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Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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3

Analysis of the Program

BIRDS

Allocation of Program Effort

The panel has analyzed the allocation of Environmental Studies Program effort among marine regions and categories of study. The eight marine regions are those listed in the section on benthic studies. The studies are divided into seven broad categories, as follows:

  • Colony inventory. Location and mapping of breeding colonies and estimates of numbers of birds of each species in each colony.

  • At-sea inventory. Surveys and mapping of distributions of birds at sea, usually based on standardized transect methods.

  • Shoreline habitats. Surveys of habitats and their use by birds in nearshore, intertidal, and supratidal zones, including studies of distribution, abundance, and feeding of birds in these zones during the breeding season and on migration.

  • Colony processes. Studies conducted at breeding colonies of phenology, reproductive success, trophic processes, recruitment and age structure, and changes in numbers.

  • At-sea processes. Studies relating the distribution of birds at sea to physical and biological features of the ocean environment, including prey numbers and distribution.

  • Exposure and effects. Studies of factors that control direct and indirect exposure of marine birds to oil and physiological and reproductive effects of exposure.

  • Modeling. Integrative models of the consequences of oil spills, including estimates of contact with bird populations and consequent mortality, physiological, and population changes.

MMS maintains records of the allocation of contracts by administrative region and by lease-sale area, but the Ecology Panel chose to examine allocation of project effort and funds by marine region and by category of ecological study. The allocation developed by the panel was based on a list of contracts provided by MMS. For projects conducted in more than one marine region or in more than one year or covering more than one category of study, the panel allocated project effort according to the following rules:

  • One project-year was assigned to each region for every year for which the project was funded.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×
  • For projects involving more than one group of animals (birds, pinnipeds, cetaceans, or turtles), the panel assumed that project funds were assigned equally to each group.

  • The panel assumed that project funds were assigned equally to each region and to each category of study listed in the project title or in titles of reports or publications.

It is recognized that these assumptions are imprecise, but they should give a reasonable approximation of the actual allocation of program efforts.

An analysis by the panel of MMS's bird studies shows that the regional allocation of bird-related effort in the MMS program has been extremely uneven. Almost all the program effort was allocated to waters off Alaska (85% of project-years and 67% of program funds) or to waters off California (12% of project-years and 29% of program funds). The large amount of program effort in Alaska was not unreasonable, in view of the large numbers of marine birds that breed there, the relatively poor initial knowledge of these birds, the drilling activity in Alaskan waters in the early years of the ESP, and the high costs of investigation there. A large amount of effort was expended in the Beaufort Sea region, which has a small number of pelagic birds breeding there, but in fact the effort was spent mainly on investigation of shoreline and lagoon habitats, where migratory birds and waterfowl are concentrated and are potentially vulnerable to OCS activities. The allocation in California of 29% of all the program funds allocated to birds appears out of proportion to the small numbers of marine birds that breed in California, but it is not; much of the work was conducted on the numerous migratory and wintering species and on effects studies that could be generalized to other regions.

Essentially no MMS studies of birds have been conducted in the Atlantic regions, although some studies have been conducted by other agencies (e.g., Erwin, 1979 (FWS); Korschgen, 1979 (FWS); Powers, 1983 (NMFS)). Only about 2% of the program's resources were allocated to studies in the Gulf of Mexico. The amounts of effort and funding allocated to the Gulf of Mexico and the Atlantic regions are much smaller than would have seemed appropriate, given the magnitude of existing or proposed OCS activity. The lack of follow-up studies of birds in areas with oil production, i.e., in the Gulf of Mexico and southern California, has made it impossible to learn the long-term effects of OCS production on birds.

The allocation of program effort among the various categories of study appears reasonable. About 31% of program funds was allocated to studies on breeding colonies, including surveys, censuses, and studies of productivity and diet. About 39% of program funds was allocated to studies at sea, mainly on distributional surveys and diet studies during the breeding season. About 17% of program funds was spent on shoreline habitat studies, mainly in Alaska, and about 11% on studies of exposure to and effects of oil. Only 3% of program funds (three projects) was spent on constructing models of effects of oil spills.

Assessment of Results

The ESP provided a major impetus for the study of marine birds in the waters of the United States. It sponsored major surveys of the distribution of seabird colonies and the distribution of birds at sea. Through those efforts, our knowledge of the distribution and abundance of breeding North American seabirds has been greatly increased, particularly in Alaska, for which only sketchy information was previously available. ESP studies of the pelagic distribution and abundance of birds were, with a few exceptions, the first systematic attempts to study the pelagic biology of seabirds in U.S. waters, and they have provided the foundation of our knowledge of the marine biology of seabirds and the data base needed by investigators to pursue more narrowly defined projects, supported by other agencies.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

In the pelagic realm, the early ESP efforts led to techniques that are now standard in surveying, data recording, and oceanographic and remote sensing. The studies of foraging distribution and trophic webs greatly increased our general knowledge of seabird pelagic ecology and provided data on which later research would be based.

In contrast, the colony-based studies did not result in the same degree of advancement of a field of study as did the pelagic work. Useful modeling exercises were carried out by the ESP, but it is not clear how lasting a contribution they will make, because of the specialized nature of the models and the apparent lack of follow-through in generalizing, validating, and applying them.

Finally, in toxicology, the ESP has funded the development of excellent new analytical techniques for detecting and identifying hydrocarbon residues and of innovative field studies of the effects of hydrocarbon pollutants. The physiological studies, although narrowly directed at the effects of oil, have increased our awareness of the sensitivity of some native species and of the importance of working with native species in the wild, rather than relying solely on laboratory tests with standard animal models.

The following evaluation provides a more critical analysis of the strengths and weaknesses of the ESP relative to its mandate for environmental impact assessment. In the broad overview, the program supported a wide variety of research endeavors that added greatly to our knowledge of marine birds in a very short period. Most of the knowledge is available in the “gray” literature, and a fairly large amount is becoming available in the refereed literature. The latter body of published material is strong evidence of the accomplishments of the ESP effort.

Selection of Species and Locations for Study

The panel was not provided with any documentation as to the methods or rationale for the selection of bird species or sites for study. Although general planning meetings were held for both the Southern California Bight region (Lavenbin and Earle, 1975) and the Alaska region (NMFS, 1975), they were too general to yield carefully designed plans (see also Bartonek and Nettleship, 1979). The selection of species appears to have been largely at the discretion of the various investigators and to reflect a combination of factors, such as ease of study and scientific interest, as well as potential vulnerability to oil. This mix of criteria seems reasonable; in most regions where there was a substantial ESP effort, the variety of species chosen provided a reasonably good coverage of the most abundant species, the species most vulnerable to oiling, and easily studied species that might be good indicators of local environmental change.

In the pelagic studies, little apparent effort was made to target selected species for study. An exception was the study of shearwaters (Puffinus spp.) in Alaska (Guzman and Myers, 1982). Generally, individual investigators singled out particular species for more thorough analysis, e.g., brown pelican, Pelicanus occidentalis, in California (Briggs et al., 1981b, 1983a). For the most part, studies were aimed at the investigation of given areas and encompassed all species present. That was usually appropriate, in that the integrated study of marine ecosystems is more likely, as a first cut, to provide a broad understanding of the multiplicity of factors that influence the pelagic distribution and abundance of birds than would the study of individual species.

The allocation of effort in the study of the breeding distribution of birds was on a colony or area basis, rather than on a species basis. Surface-nesting and cliff-nesting species received the best coverage, and burrow-nesting (particularly nocturnal) species received less complete coverage. Nocturnal species are very difficult to count, and the sizes of their populations remain

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

poorly known. To the extent that nocturnal species are potentially very vulnerable to oil pollution, more attention should have been paid to assessing the location and size of their nesting populations.

In the colony-based studies of reproductive and trophic ecology, many factors appear to have influenced which colonies were chosen initially and the selection of species for study. Large colonies, important centers of the population of a given species, and accessibility were considered important. In no region was there a detailed plan at the outset for the coverage of particular species or a particular set of “representative” colonies. However, in most colonies investigated, a mix of species was used, including surface or cliff nesters and species that dive in pursuit of prey (alcids) and forage at or near the surface, often while airborne (kittiwakes, gulls, and terns). Studies of storm petrels, fulmars, and nocturnally active alcids were few and narrowly distributed.

Conspicuously absent from the ESP for marine birds are studies of the several endangered or threatened species that occur in lease areas or habitats adjacent to OCS areas. We found no studies focusing on the short-tailed albatross (Diomedea albatrus), cahow or Bermuda petrel (Pterodroma cahow), California brown pelican (Pelecanus occidentalis) (although aspects of pelican biology were addressed in several California studies), Aleutian Canada goose (Branta canadensis leucopareia), snowy plover (Charadrius alexandrinus), California least tern (Sterna antillarum browni), roseate tern (S. dougallii), or the various threatened or endangered salt-marsh-inhabiting species, including some of the subspecies of the clapper rail (Rallus longirostis) or the various salt marsh sparrows. If anything, the endangered marine bird species appear to have been avoided as subjects of study in the ESP. In some cases, attempts to direct studies toward endangered species would have been futile, because of the small numbers present in OCS waters (e.g., short-tailed albatross). In other cases, the failure to examine carefully the potential impacts of OCS development on endangered and threatened bird species potentially vulnerable to OCS activities was a serious oversight.

The rationale for the selection of colony sites for process studies and at-sea areas for both inventory and process studies is unclear. For colony process studies, we know of no attempt at the outset to select a representative group of major colonies in each OCS region, let alone in each marine domain, for careful, long-term study. Most colonies in most regions were studied for short periods, 1-3 years, and sometimes for less than one full season. This dispersed, fragmented approach dissipated resources and led to a diversity of data, most of which are too incomplete to provide a clear picture of the degree of natural variation in the system. After the first year or two of the program in each region, it would have been appropriate to select, in cooperation with other concerned state and federal agencies (U.S. Fish and Wildlife Service, and various state fish and game departments), the one or two most important colonies in each ecological domain on which to focus long-term attention (for the duration of the OCS program). An extremely productive effort of that sort, which took place in the fall of 1984 in Alaska for studies in the Bering Sea, included not only federal and state scientists but others, as well. However, this and later efforts came almost 8 years or more too late for influencing the major ESP efforts in Alaska. We are unaware of any equivalent cooperative planning process that was used to assess progress and to develop recommendations for priorities for future seabird work in any other OCS region.

The sites for pelagic inventories of marine birds and pelagic process studies were decided more by the dictates of other programs in charge of ship use than by needs for adequate coverage to discern where and why marine birds might congregate at sea. Relatively little work was devoted to studying the distribution of vulnerable species (e.g., alcids) foraging near major colonies; efforts at the Pribilof Islands (Hunt et al., 1981a), at Kodiak Island (Gould

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

et al., 1982), and in the Southern California Bight (Hunt et al., 1979) were exceptions. For other areas, MMS obtained few or no data on where birds from important colonies might be expected to concentrate their foraging. Such data are essential for developing an appropriate environmental impact statement (EIS) for the protection of critical foraging areas, and for the protection of the colonies from spilled oil. Birds are not distributed randomly but are aggregated with respect to physical structures. Two major instances of aggregation in predictable locations are in the vicinity of fronts and where currents impinge on bathymetry of high relief, causing prey to aggregate and become more available to birds. To the extent that such areas are near colonies or are along migration routes, it can be expected that large numbers of birds will be concentrated in small areas. MMS should focus on process studies within foraging range of colonies and in known major migration routes to determine where predictably large concentrations of birds will occur.

Colony Inventories

Inventories of seabird colonies are now available for most of the coasts of the coterminous United States. The inventories were sponsored by MMS in Alaska (Sowls et al., 1978) and California (Sowls et al., 1980) and by the Fish and Wildlife Service (FWS) in Washington and Oregon (Varoujean, 1978), the Gulf of Mexico (e.g., Keller et al., 1984), and the Atlantic coast (e.g., Erwin and Korschgen, 1979). Additional surveys have been sponsored by the U.S. Army Corps of Engineers (e.g., Buckley and McCaffrey, 1978; Chaney et al., 1978; Peters et al., 1978; Schreiber and Schreiber, 1978). Together, the atlases and reports based on those surveys are an excellent source of information on areas where breeding seabirds were concentrated and where densities of seabirds were low, at least at the times when the surveys were conducted. However, MMS was unable to furnish the panel with maps depicting distribution and abundance of breeding birds; the lack of such maps limits the ability to retrieve information on birds at risk in the event of a major OCS oil spill or for use in planning or running quantitative oil-spill risk models. Recently, however, a computer mapping and analysis system was developed by FWS and NMFS for analyzing the spatial and temporal distribution, abundance, and life history of breeding colonial seabirds on the west coast of North America from California to Alaska. The data base for this system includes information from MMS-sponsored inventories (FWS/NMFS, 1991).

Although the panel considers the available knowledge of colony locations and sizes adequate for assessing the potential for damage from OCS activities (i.e., as the basis for estimating risk), the available data are inadequate as the basis for assessing change (including measurement of impacts of actual events). First, the methods for estimating population size within colonies have been crude at best. Many colonies were surveyed only from a boat or from a passing aircraft. The surveys established where large numbers of surface- and cliff-nesting species were, but gave little information about burrow-nesting, particularly nocturnally active species. Estimates of numbers in the largest “supercolonies” are particularly uncertain. Although marked plots have been established in a small number of breeding colonies in Alaska (mostly by FWS, independently of the ESP), the relationship of numbers within these plots to colony size and regional populations is poorly understood. Hourly, daily, seasonal, and annual changes in numbers within study plots and within colonies are relatively large and are difficult to control for (Wanless et al., 1982). Thus, baseline measures of sample or regional populations are imprecise. Second, most of the regional surveys have been conducted only once. Movements of birds between colonies would confound attempts to infer regional trends from

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

sample counts, but these movements have not been investigated for any species in the MMS program. Finally, counts are available only for breeding birds: the proportions of prebreeders and nonbreeders are unknown. In virtually no cases have surveys been accurate enough or counts been repeated enough to provide the means to detect any but the largest or most sustained changes in population size. The few exceptions to that generalization are long-term studies of individual species funded by agencies other than MMS (see Hunt, 1987; Nisbet, 1989).

At-Sea Inventories

Techniques for the at-sea survey of birds from both ships and aircraft were developed at the outset of the ESP (e.g., Briggs et al., 1981a). The newer surveys improved on many studies done elsewhere, in that they used a format that reduced (but did not eliminate) the problems of differential detectability of species and variations in visibility related to observers' height above the water and weather conditions. Aerial remote sensing of oceanographic characteristics coupled with observations of pelagic birds constituted an important method not only for describing bird distribution, but for testing hypotheses concerning the mechanisms responsible for the patterns observed (Briggs et al., 1987). The latter information is important for understanding whether the patterns observed are likely to be regular and frequent.

The surveys of the distribution and abundance of marine birds at sea varied greatly from one marine region to another in spatial and seasonal coverage. No up-to-date maps showing the distribution of sampling effort by marine region and by season or maps of seabird distributions are available from MMS, although maps showing the areas covered by specific studies are available in the final reports of completed studies. Most parts of the continental shelf off Alaska received at least some coverage, particularly during the summer season. The Alaskan studies provide a good general overview of seasonal shifts in the distribution of birds and a preliminary indication of spatial patterns of abundance (Hunt et al., 1981b; Gould et al., 1982).

Coverage of the coast and the waters off California has been excellent, and both seasonal and spatial patterns of distribution are known (Briggs et al., 1981a, 1983b, 1987). No MMS studies of pelagic distributions of birds off the Oregon and Washington coasts have been published, although a study of this region is to be completed in 1991.

In the Gulf of Mexico, surveys of the distribution of marine birds have provided poor coverage of the area and only fair coverage of seasonal patterns of abundance. A pilot study (Fritts and Reynolds, 1981) provided aerial coverage of four small areas in August and December 1979, and a followup study covered these areas with a series of seven surveys between June 1980 and April 1981 (Fritts et al., 1983). In all, the study involved approximately 45 days of flying; about half the flights were at an altitude suitable for bird observations (91 m) and about half at a higher altitude (228 m), more suitable for spotting marine mammals.

There appear to have been no MMS-sponsored surveys of marine bird distribution along the southern and central Atlantic coasts or for Georges Bank or the Gulf of Maine. However, much of this area has been surveyed by other agencies (e.g., Powers, 1983 (NMFS); Brown, 1986 (Canadian Wildlife Service)). Although sampling methods were standardized for MMS-sponsored studies on the Pacific coast and in Alaska, different methods were used in the surveys of the Gulf of Mexico and Atlantic waters. The lack of uniformity of data collection and storage prevents the construction of a nationwide data base, although some regional data bases are being maintained. To the panel 's knowledge, data from the Gulf of Mexico and Atlantic coast have not been incorporated into an MMS data base, from which they could be retrieved (e.g., for real-time response to an oil spill or for planning purposes, such as inclusion in a quantitative oil-spill risk model).

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

Examination of the available data on pelagic distributions of birds reveals that data on bird densities (transect counts) for relatively large areas consist of small numbers of counts with high among-count variances (e.g., Hunt et al., 1982). Even in the areas with the best coverage (Alaska and California), the data are useful only to provide a general picture of the patterns of spatial and seasonal abundance and hence to identify general areas in which bird populations might be at special risk. Because the samples are small and the variance-to-mean ratios (reflecting the patchiness of bird distributions) are high, the data are, for the most part, statistically inadequate to provide a reference against which to measure change.

Shoreline Habitat Inventories

MMS-funded surveys of inshore waters and intertidal and supertidal areas are limited in coverage and distribution. In Alaska, there have been extensive surveys of habitat availability (Arneson 1980), but only fragmentary studies of use of the habitats by birds. Parts of the Beaufort Sea coast have been well studied (e.g., Connors et al., 1981; Johnson, 1983), as have parts of Norton Sound (Drury et al., 1981), the Yukon Delta (Eldridge, 1987), the north coast of the Alaska Peninsula (Troy and Johnson, 1987), and some areas in the Gulf of Alaska where major migratory stopovers have been identified (reviewed in DeGange and Sanger, 1987). For the most part, however, use by birds of the coastal zone of Alaska remains poorly known because of extreme logistic difficulties. In the 48 states, MMS has provided partial support of beach and inshore bird surveys in the Southern California Bight and in a small portion of the Gulf of Mexico, and other agencies have sponsored beach surveys in central California. Most coastal areas remain unsurveyed.

MMS has sponsored studies of the distribution of beach-cast carcasses of oiled birds in California (e.g., Stenzel et al., 1988) and on a small portion of the gulf coast of Texas, but few elsewhere. Recent studies of the proportion of oiled carcasses that actually reached the beach indicate a great deal of short-term variability in the likelihood that a carcass would reach the beach and be found (Page et al., 1982). Without extensive concurrent data on winds, currents, and carcass flotation, beached-bird surveys are of little value as measures of mortality and are of only modest value as a reference for future monitoring.

Colony Process Studies

Process studies conducted on colonies include measurements of phenology, diet, chick growth, and productivity; variations in these characteristics can be correlated with environmental factors, such as temperature and prey availability. Measurement of additional characteristics —such as survival, age at first breeding, recruitment, and dispersal —can then provide the basis for construction of models of population structure and of the relationship of population change to environmental factors. Because most seabirds are long-lived, total population size and colony numbers are less sensitive to short-term changes in the environment than are process measures, such as clutch size, chick growth rates, and productivity. Process studies are therefore essential, if effects of local or short-term environmental changes are to be detected.

Colony process studies can provide information on the natural range of variation in system characteristics, an early warning of potential problems, and a means of detecting and predicting changes caused by environmental factors other than OCS activities. Properly executed, they can provide a historical record against which to measure change. They can also

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

be useful in increasing our understanding of the environmental correlates and natural causes of changes in reproductive and trophic biology of selected species. Colony process studies are essential as sources of data for constructing predictive models of impacts of OCS activities. Colony studies are unlikely to provide the basis for attributing specific observed changes to the effects of OCS activities, but might be useful in providing alternative explanations when changes are observed.

To be of greatest value, colony process studies need to be carried out over long terms and be incorporated into monitoring programs. Within the ESP, however, most colony process studies have lasted only 2-4 years. In Alaska, colonies of various species have been studied for longer periods with support from MMS in some years and from FWS in others (e.g., Cape Lisburne, Pribilof Islands, and Prince William Sound). In California, MMS supported one 3-year study in the Southern California Bight that was continued with funds from other sources. In central California, one 19-year study at the Farallon Islands supported by non-MMS funds is going on now (Ainley and Boekelheide, 1990).

In the panel's opinion, the colony process studies conducted under the ESP yielded much less valuable results than could have been obtained with better allocation of the same funds. The lack of a coherent plan and of a commitment to long-term studies at strategic locations at the outset has resulted in a large number of studies of short duration, many of which cannot be interpreted or integrated into an overall understanding of colony processes. Many of the studies were terminated 5-10 years ago; in the absence of recent followup, it is not clear whether the early results can be used to predict or evaluate impacts of OCS activities. Properly planned and executed, colony process studies could have been invaluable in identifying short-term changes and in correlating them with environmental changes. Without continuing studies, it will be difficult or impossible to identify natural causes of observed changes and hence to rule out OCS activities as causes of these changes. The ESP made a good start on thorough process studies at several colonies; the program is deficient in that it did not follow up this good start by shifting efforts at some of the sites to a continuing monitoring program designed for the duration of OCS activities in the selected areas, as is required by OCSLA as amended in 1978.

At-Sea Process Studies

In the context of the ESP, the primary function of at-sea process studies is to aid in understanding the observed patterns of avian distribution and abundance. Such understanding, based on elucidation of underlying processes, should help in the prediction of the degree of aggregation of at-sea populations and prediction of the locations of aggregations in specific circumstances. Process studies should integrate information across trophic levels and should ultimately be grounded in the understanding of physical and biological processes in the ocean.

Most at-sea process studies of marine birds conducted in the ESP are of only limited value in serving those functions and were not designed to do so. In Alaska, most at-sea process studies investigated food habits of birds, but did not integrate the resulting information with physical data or data on prey availability. However, in the California studies, information on physical processes and chlorophyll concentrations obtained with remote sensing was combined with shipboard collections of data on the foods available and taken by birds in areas of seabird abundance to provide a picture of why particular species concentrated where they did (Briggs et al., 1987). The panel knows of no MMS-funded studies of the effects of marine processes on seabird distribution and abundance other than those in Alaska and California.

In nearshore and shoreline habitats, data were gathered on the foraging of seabirds and

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

shorebirds along the Beaufort Sea coast (Connors et al., 1981) and in the coastal regions of the Gulf of Alaska (Senner, 1979). Those studies provided useful information on feeding sites, foods, and fat deposition of migrating shorebirds and yielded an assessment of the importance of the studied habitats to the successful completion of migration by the species. Studies of the use of coastal lagoons by waterfowl also provided valuable information on the use of the specific lagoons for the successful migration of the species and populations that used them. The process studies in the intertidal zone have yielded data essential for assessing the vulnerability of areas used as staging areas by important populations of shorebirds and waterfowl.

Effects Studies, Modeling, and Estimation of Risk

The MMS program has put only a small percentage of its seabird program effort into investigations of the potential effects of OCS activities on birds. The studies that were funded included investigations of the incidence of oil ingestion by storm petrels (Boersma, 1986) and of reactions of birds to oil and incidence of oiling (Varoujean et al., 1983), field studies of the effects of ingested oil on reproduction in alcids and petrels (Fry, 1987), studies of recovery rates of two species of birds on the Pribilof Islands (Ford et al., 1982), and a series of risk-assessment models, primarily for the Southern California Bight (e.g., Ford, 1985). Studies of the effects of the IXTOC-I oil spill on the coast of Texas showed decreased use of beaches by shorebirds and fouling of plumage and accumulation of globs of tar on the feet of gulls, terns, and shorebirds, including threatened and endangered species (A. Amos, Texas A & M Marine Station, pers. commun., 1991). On the whole, those efforts appear to have been useful. The panel considers the opportunistic use of wild species of seabirds in the field for toxicity studies to be a marked improvement over laboratory studies of waterfowl or other model species—species that might differ substantially in susceptibility to toxic effects of oil from the wild species that are at risk. However, there appears to have been a lack of followup in efforts that might be most useful. Although excellent techniques for the detection and identification of hydrocarbon compounds in tissues were developed, we know of no continuing, regular monitoring for contamination of bird tissues in any OCS region currently producing oil or gas or in areas near major transportation corridors.

Several attempts were made to delineate “risky” areas on the basis of observed seabird distributions and on the basis of measures of patchiness. They included useful innovations in risk characterization, but the approach has not been followed up with applications throughout the several OCS regions. In particular, the risk modeling conducted for the Southern California Bight (Ford, 1985), although promising as a tool for identifying and measuring possible outcomes of a hypothetical oil spill, does not appear to have been followed up or generalized to other OCS regions. Thus, an opportunity to develop generalized risk models has not been exploited adequately. Likewise, there seems to be little attention to the effects of chronic contamination of low magnitude or of chronic disturbance.

Gaps in the Available Data

The panel sought to identify data deficiencies that were of central concern with respect to the goals of the ESP. The minimal program of studies that should have been included in the ESP from the start can be summarized as follows.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×
Colony Inventories

There are no known gaps in the inventory of seabird colonies. But almost none of the inventory counts provides a statistically adequate historical record against which to measure changes in population size. At too few colonies has there been the repetition of counts between years, let alone within years, needed for statistical soundness. Many surveys are now over 10 years old. The panel is aware that MMS is beginning to update colony censuses.

At-Sea Inventories

Large areas of the OCS have received little or no MMS coverage. We have almost no information on the birds at risk in those areas. The lack of coverage in the Gulf of Mexico is perhaps the most glaring deficiency; up-to-date survey data are also needed for Georges Bank. In some areas that have received coverage, the seasonal distribution of counts is uneven. The lack of surveys in Alaska during winter is of concern. Although such surveys are logistically difficult, winter is a time when birds might be concentrated in coastal areas or near the ice edge and thus be particularly vulnerable to spilled oil.

Coverage of most areas has been insufficient to detect major at-sea migration routes and staging areas. The passage of birds on migration is a transitory phenomenon during which major segments of the population of a species can be concentrated in small, traditionally used locations for brief periods. The locations and the timing of their use might be known to local residents, but are probably not known to MMS.

Shoreline Habitat Inventories

The inventories of the shoreline habitat and nearshore waters throughout most OCS regions are generally insufficient to let MMS assess the potential risk of impact or the actual loss of birds if an oil spill occurs; data gaps appear particularly severe for the coasts of the Gulf of Mexico, the middle and south Atlantic seaboard, Cape Cod, and the Gulf of Maine. Data are also apparently unavailable for the northern California, Oregon, and Washington coasts.

Colony Process Studies

Information on age-specific mortality, fecundity, and recruitment —critical for the construction of population models—is lacking. There are no data on dispersal, and there are no continuing long-term studies of reproductive ecology and its relationship to environmental change.

At-Sea Process Studies

With few exceptions, there is insufficient knowledge of the major foraging areas near large colonies and of the degree to which they are geographically fixed because of topographically driven marine processes. Information is lacking on the physical and biological processes that result in predictably greater availability of prey in particular locations.

More knowledge of the processes that determine the location of major concentrations of

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

migrant and wintering birds is needed. At-sea processes responsible for concentrating birds have been best studied in the Bering Sea, central California, and Georges Bank, but are not well known for other regions.

Shoreline and Nearshore Process Studies

For many, if not most, of the known major staging areas, the energetic consequences and the resulting impact on bird populations of the partial or complete loss of what are thought to be critical habitats for both waterfowl and shorebirds are unknown.

Effects

There are insufficient data on the behavior of birds at oil slicks. Too few species have been studied, and the data on those studied are inadequate for predicting the proportion of birds likely to encounter oil in the event of a spill.

There is little or no information on factors that control the rates at which oil will be ingested and on whether oil is likely to be ingested primarily with food or through other activities, such as preening.

There is a lack of knowledge of the generality of the hemolytic and reproductive effects found by Fry (1987) in the full range of wild birds likely to be exposed to oil.

It is not now possible to assess the full number of birds killed in a spill with accuracy.

Data on the present prevalence of oil contamination on and in live birds in the wild are sparse. Spills that occur should be used as study opportunities to obtain these kinds of data.

Models and Estimation of Risk

The means are lacking to predict the number of birds at immediate risk because of any particular oil spill, other than one in the Southern California Bight, and even the risk-assessment model for the Southern California Bight lacks validation. It is not yet possible to relate episodic events, such as mass deaths in an oil spill, to population structure and consequent changes in populations.

Recommendations for Future Research

The panel identified the kinds of data needed if the goals of the ESP are to be met fully. Some of the required studies, however, are not feasible, given the length of time needed for their completion, the cost in relation to the information they could yield, or logistic problems that almost certainly would preclude success. The panel therefore recommends below the studies that are most urgently needed for addressing the central goals of MMS, but tempers its recommendations with considerations of feasibility and cost-effectiveness.

Colony Inventories

There needs to be a single, integrated data base in which all information on location, species composition, and population size is recorded and from which data can be retrieved for

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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planning and for immediate use in case of a spill or other accident. MMS should select a subset of vulnerable or potentially vulnerable colonies for the creation of a statistically based historical record and monitoring program in which surveys of representative colonies will be kept up to date.

At-Sea Inventories

The most critical need is to integrate, to the extent possible, existing data bases and to create a real-time retrieval of data on the at-sea distribution and abundance of birds at any OCS location in any season of the year.

MMS should conduct at-sea surveys of marine bird distribution and abundance in regions with oil exploration or continuing oil development that lack adequate, up-to-date pelagic inventories and in other regions that lack pelagic inventories. It should also conduct focused studies of migratory routes to identify areas and timing of concentrations of birds, e.g., in the Straits of Florida, Bering Strait, and Aleutian Passes (a Unimak Pass study is in progress). Some at-sea distribution and survey data can be collected on platforms of opportunity, while some work might require dedicated research vessels. MMS should work cooperatively with NMFS, FWS, and relevant state agencies to plan cooperatively and carry out multi-disciplinary studies in regions of mutual interest and concern.

Shoreline Habitat Inventories

There is a need for a systematic inventory of shoreline regions used by birds near shore facilities or where oil-spill trajectory models suggest that oil might come ashore. Surveys of areas of such potential impact need to include not only avian use of salt marsh, lagoon, and intertidal flats and beach, but also nearshore waters to 5 km offshore.

Colony Process Studies

The panel recognizes that data on age-specific fecundity, recruitment, and mortality are important, but it is not practical to begin a project intended to measure them at this late stage in the ESP program. For most important species in Alaska, that would require a huge effort for at least 5 years to study recruitment, and 10-20 years to study age-specific mortality and fecundity. However, in a few cases, species might be relatively easily studied (e.g., eider ducks on the North Slope and pigeon guillemots in the Gulf of Alaska). In other cases, existing long-term studies of marked populations of known-age birds could be used for the construction of life tables (Nisbet, 1989). The life tables would be valuable for predicting the impact of oil-related activities on populations of the studied species and, by extension, other species.

MMS should give high priority to seeking cooperative agreements to construct life tables with investigators who have extensive populations of known-age marked birds. Species and locations that would be appropriate include black guillemots on the North Slope, various species on the Farallon Islands, various terns on the East Coast of the United States, brown pelicans in California, and possibly the Leach's storm petrel in the Gulf of Maine. MMS should seek cooperative agreements with the Canadian Wildlife Service, which has continuing, long-term

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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studies of seabirds. Clearly, all available data sets should be used in designing a comprehensive program for studying bird colony processes.

At selected colonies of selected species, MMS should conduct annual studies of selected reproductive characteristics, including phenology, clutch size, chick growth, production of young, and food used. The monitoring studies should extend until the end of OCS activities in the area. At least one representative colony in each oceanographic domain with at least one species of each foraging type, to the extent practical, should be investigated. If suitable colonies are available for study, the panel suggests a minimum of one colony in the Chukchi Sea, two in the Bering Sea, and two in Prince William Sound, one in the Gulf of Alaska, one in northern California, one in southern California, and one in the Gulf of Mexico. The panel sees the resulting data as more important for monitoring the status of populations than mere counting of birds at colonies.

At-Sea Process Studies

MMS should conduct studies of the processes that affect the at-sea distribution of foraging birds near major colonies that are potentially exposed to oil spills from OCS activities. MMS should locate and study the spatial and temporal scales of processes responsible for the at-sea aggregation of seabirds, so that it can develop models capable of predicting the consequences of spills. The process studies should focus on areas where birds concentrate in active lease-sale and production areas. Information from other scientific disciplines must be integrated in the development of the new process studies; available at-sea marine bird data bases should be re-examined, so that it can be determined whether identified areas of concentration correspond with the location of known oceanographic processes or features. When possible, studies of oceanography, fish, resources, birds, and marine mammals should be planned and carried out cooperatively to develop comparative data sets and make the best possible use of available ship, aircraft, and other resources.

Shoreline Process Studies

For the major staging and wintering areas, MMS should measure the energetics of birds and model the potential impact of partial or total losses of staging areas on populations. For major staging and wintering areas, MMS should determine the relationships among density, number, residence time, and food availability and, if local food availability is found limiting, the behavioral mechanisms that regulate numbers of birds. Such information is needed particularly for waterfowl that winter inshore.

Effects and Risk Studies

MMS should improve its ability to use real oil spills, regardless of source, to study the behavior of birds on their first contact with spilled oil, and its physiological effects in the wild, as well as long-and short-term responses to oil spills and clean-up activities. This would require a contingency plan for real-time studies, preferably in cooperation with other responsible agencies. This point applies to marine mammals, fish, and other species groups, as well as birds.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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There is a need for testing of more species of birds in the wild (e.g., shearwaters, alcids, and sea ducks) for sublethal toxic effects, such as reproductive failure and hemolytic anemia. For species shown to be vulnerable, factors controlling exposure should be investigated.

Studies of the movements of dead birds at oil spills should be conducted to help in determining what happens to bird carcasses. Further work is also needed to interpret the significance of the number of oiled birds on a beach relative to the population at risk or actually affected.

The presence of oil and oil residues in the tissues of selected species should be monitored at selected colonies.

Modeling Studies

MMS should develop and validate models designed to show how many birds are likely to be at risk in connection with any spill in an OCS area in any given season and the significance of the number of dead birds relative to the population that is at risk or is actually affected. The models should include both breeding and nonbreeding birds and should incorporate data on foraging distributions around colonies, as well as data on nonbreeding, or “passage” birds. Validation of the models with appropriate pelagic surveys (which could be combined with other survey programs) is essential.

On the basis of data acquired in process studies, life tables should be developed to relate adverse changes in survival or productivity to long-term population size and recovery rates; at the least, this will require extension and generalization of the model by Ford et al. (1982).

Criteria are needed for determining the smallest size effect regarded as “significant.”

Coordination, Cooperation, and Organization

In discussions with MMS personnel, principal investigators, and people in various agencies, it became apparent that, at least within the marine bird studies, there has not been an overall ESP plan of work that has coordinated efforts among the various OCS regions, other federal and state agencies, and university-based investigators funded from other sources. Planning sessions involving knowledgeable people capable of setting priorities and making commitments have not been held regularly. Without such meetings at which priorities are decided and workplans are developed, coverage and effort become uneven and discontinuous. Without followup and development of processes for information transfer, data gathered in research not funded by MMS fails to be included in MMS data banks and reports. MMS needs more data than it can afford to acquire. The availability of mechanisms and inducements to investigators for sharing data (e.g., covering the cost of reformatting data tapes) could yield a wealth of information of value to the MMS planning and monitoring program. Likewise, data gathered by MMS could be of value to other federal and state agencies. The lack of formal mechanisms for sharing data and coordinating efforts is an aspect of the ESP that requires improvement.

SEA TURTLES

The Cetacean and Turtle Assessment Program, the MMS-funded study known as

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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CETAP (Winn, 1982), is discussed in the marine mammal section. It was conducted between 1978 and 1982 and covered the area from Cape Hatteras to the Canadian border, extending to just beyond the 1,000-fathom (1,830 m) isobath. The survey provided important data (now in need of updating) on the seasonal distributions of sea turtles in those waters and would have provided a reasonable basis for assessing the likelihood that turtles would come into contact with spilled oil.

The available information on the at-sea distribution of turtles farther south in the Atlantic Ocean and in the Gulf of Mexico is much less satisfactory. Fritts and Reynolds (1981) conducted a pilot aerial survey in the Gulf of Mexico, and it was followed by aerial surveys in the gulf and off the southern Atlantic coast in 1980-1981 (Fritts et al., 1983). Those surveys were too limited in scope and techniques to provide more than fragmentary information on turtle distribution. In 1989, MMS convened a workshop to plan future studies on sea turtles and marine mammals in the Gulf of Mexico. Workshop participants concluded that an information base needs to be developed to create models that would predict actual and potential human impacts, that distribution and abundance studies should examine habitats associated with different life history stages, in particular the pelagic habitat, and that priority should be given to the Kemp's ridley (Tucker and Associates, Inc., 1990).

Another NRC committee has recently reviewed the available data on sea turtles in U.S. waters, including information on causes of the recent decline in numbers of some species (NRC, 1990b). All five species that occur in U.S. waters are listed as endangered or threatened and are protected under the Endangered Species Act. Although much is known of their breeding distribution, of population trends, and of some aspects of their ecology (Bjorndal, 1981; NRC, 1990b), information on their at-sea distribution and vulnerability to oil is only fragmentary, especially for the Gulf of Mexico. Turtles appear to be attracted to oil platforms, especially east of the Mississippi River (Lohoefener et al., 1990), and there is evidence that the use of explosives in the removal of platforms kills turtles swimming nearby (Klima et al., 1988). The NRC committee (1990b) estimated, with considerable uncertainty, that oil-platform removal might cause 10-100 turtle deaths each year in U.S. waters “without protective intervention. ” Although it cited no other information on oil-related mortality of turtles, ingestion of oil and tar balls has been blamed for the deaths of young green turtles in Texas and Florida (Witham, 1981; Woody, 1986). The oil spill resulting from the IXTOC I blowout in 1979 probably affected Kemp's ridley turtles near their only known nesting beach in Mexico (Waldichuk, 1980), but the effects were not adequately investigated.

MMS's investigations of sea turtles, especially in the Gulf of Mexico, have been inadequate in view of the listing of the populations of these species in U.S. waters as endangered and their apparent vulnerability to OCS activities, although it has recently supported a study of the associations of turtles with oil platforms (Lohoefener et al., 1990). As pointed out in a recent NRC report (NRC, 1990b), available information on sea turtles in the Gulf of Mexico is inadequate as a basis for assessing potential effects. Lohoefener et al. (1990) also recommended additional studies of sea turtles in the Gulf of Mexico, especially east of the Mississippi River, to better assess the risk to them of platform removal.

Although little is known of sea turtle life history during the post-hatching phase (NRC, 1990b), it is reasonable to expect that young loggerheads and Kemp's ridleys and perhaps other turtle species reside in the sargassum community, where currents converge in the Gulf Stream. Oil spilled during normal operations as well as oil from larger spills is likely to become concentrated in the convergences that also concentrate sargassum. Given the recent leasing and proposed OCS leasing for sites within the Gulf Stream, MMS should survey the sargassum community to determine the distribution and abundance of turtles there.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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MARINE MAMMALS

Introduction

This section discusses the adequacy of the Environmental Studies Program for marine mammals—whether, in combination with data available from other sources, the ESP has provided a basis for an informed decision about the potential impacts of OCS petroleum operations. Marine mammals are especially important, because many are endangered species (e.g., many large whales, sea otters, and manatees); some have cultural, subsistence, and economic importance to Native American groups; many are highly valued by the public (e.g., dolphins, whales, polar bears, and baby seals); and all are protected by the Marine Mammal Protection Act. They can also be extremely difficult to study —all are highly mobile, none is a good “laboratory” species, and all are relatively long-lived. Previously, there had been few large-scale synoptic surveys in U.S. waters, so there was little foundation of information on which to build. Acquiring the data necessary to permit reasonable environmental assessments has presented a major challenge to MMS.

MMS has a general responsibility to understand what marine mammals are present within areas that are leased for exploration, their ecological relationships, and the potential impact of offshore petroleum operations on them. These studies should focus on the most sensitive and vulnerable species, life history stages, and processes. MMS should not however, as a rule, assume responsibility for collecting the data necessary for an understanding of the population dynamics of marine-mammal populations in all U.S. waters or conduct research on populations that have been adequately studied by other organizations.

We have subdivided our analysis into three parts: inventory, effects, and ecological processes. The first part deals with whether the spatial and temporal sampling of mammal populations has resulted in an acceptable description of the stocks, including seasonal patterns of distribution, movement, and abundance. The second part is related to the understanding of the effects of contact with hydrocarbons or other pollutants and of responses to noise and disturbance. The third is related to population dynamics and the ecological relationships that affect the distribution, abundance, and population trends of marine mammals.

Environmental Studies Program and Results
Inventory

Inventories of the species of marine mammals present and the seasonal patterns of their distribution and abundance are of fundamental importance in evaluating potential impacts. Because many marine mammals are migratory and inhabit remote locations, MMS has funded major aerial survey programs over the last decade. In fact, MMS has been the largest source of funding for studies of cetacean distribution and abundance in the United States. Its programs have been carried out in all the major frontier OCS areas.

At the outset of the Environmental Studies Program, little was known about the distribution, movement patterns, and relative abundance of cetaceans in OCS waters. The migration corridors and areas used seasonally were virtually unknown for most species. For preparing accurate EISs, it was important that information be obtained on whale presence in OCS waters. Consequently, major survey programs have been conducted in nearly all OCS areas, although not all were funded by MMS.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Studies of pinniped and sea otter distribution and abundance have often been combined with surveys of cetaceans and less commonly with surveys of seabirds. Almost all the surveys of pinnipeds have been conducted off the West Coast or in Alaskan waters. Estimates of abundance of pinnipeds, particularly of harbor seals and gray seals, along the East Coast have not been funded by MMS, but have been funded by other federal agencies, such as the Marine Mammal Commission, or private research foundations (Prescott and Gilbert, 1979; Payne and Selzer, 1987). The effort in the Pacific region has been focused on the California coast, although a study of the OCS off Washington and Oregon is now under way. Studies in the Alaska region have been conducted in the Gulf of Alaska, the Aleutian Islands, and the Bering, Chukchi, and Beaufort seas. The MMS-funded surveys have been complemented by a report on the status of 10 marine mammals in Alaskan waters (Lentfer, 1988) funded by the Marine Mammal Commission. All those accounts, each with special research and management recommendations, constitute a valuable compendium of recent information on distribution, population dynamics and trends, and conservation issues and needs. Most consider possible consequences of oil and gas development.

The MMS-funded surveys have been largely successful, but expensive. They resulted in descriptions of seasonal patterns of use, particularly by cetaceans, that have in some instances led to additional research on the role of these mammals in marine ecosystems. For example, MMS contracted with the University of Rhode Island to conduct a major survey program of the mid-Atlantic and North Atlantic areas from 1978 to 1982 (Winn, 1982); the study is popularly known as CETAP, the Cetacean and Turtle Assessment Program. The study area extended from Cape Hatteras, North Carolina, to the border with Canada and seaward to just beyond the 1,000-fathom (1,830 m) isobath. Data were collected through aerial survey, from observers placed aboard “ships-of-opportunity ” and “aircraft-of-opportunity,” and from chance observers.

CETAP resulted in a much-improved picture of the distribution of whales and dolphins in the mid-Atlantic and North Atlantic regions, and this has led to more detailed work, some of which is associated with the whale-watching industry that has recently developed there. The Great South Channel has been identified as an area of particularly high use by right and humpback whales. Similarly, the feeding concentrations of blue and humpback whales that were discovered through MMS surveys in the waters off northern California have become the subjects of detailed studies (Calambokidis, et al. 1990a,b). CETAP data were less reliable for small cetaceans than for large ones and no additional surveys were supported by MMS. Surveys directed at small cetaceans that replicate the CETAP study design are being conducted by NMFS (Gerald Scott, NMFS, SE Fisheries Center, Miami, Fla., pers. commun., 1991). The study will also include sampling in the South Atlantic and Gulf of Mexico.

Surveys of marine mammals in the Atlantic south of Cape Hatteras and in the Gulf of Mexico have been much less complete than those conducted elsewhere in the U.S. OCS. The Fish and Wildlife Service, on behalf of MMS, prepared a report on the marine mammals from Cape Hatteras south to the Florida Keys (Fritts et al., 1983). The report was based on aerial surveys in an area of 111 x 222 km off the central east coast of Florida during 1979, 1980, and 1981 and on other information. FWS also conducted surveys in the Gulf of Mexico in three rectangular areas; surveys were conducted every 2 months in the last year of the program. The areas measured 222 x 111 km, with the long axis perpendicular to the coast. One area was off the coast of Texas, near Brownsville; the second off the Louisiana coast, near Marsh Island; and the third off the west coast of Florida, near Naples (Fritts et al., 1983). Those surveys made up the first systematic offshore study of cetaceans in the Gulf of Mexico, but because the effort was far less than that in other studied areas, we do not believe that the information on cetaceans in the Gulf of Mexico is adequate. However, MMS has recently undertaken more extensive

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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cetacean surveys in the Gulf of Mexico. Quantitative information is also needed on the use of the South Atlantic by right whales for calving purposes. An aerial survey of bottlenose dolphins was conducted by NMFS from 1983 to 1986 (Gerald Scott, NMFS, SE Fisheries Center, Miami, Fla., pers. commun., 1991).

For the region off the California coast, surveys of marine mammals and seabirds were combined (Dohl et al., 1981, 1983). Generally, they were intended to obtain an indication of the species present at different times of the year, and they were carried out with aircraft that flew transects along the California coast and with various survey designs. Bonnell et al. (1981, 1983) surveyed the California coast for distribution and abundance of marine mammals and seabirds; one study (1983) concentrated primarily on pinnipeds and sea otters along the central and northern California coast. Their transects were perpendicular to the coast to a distance of about 250 km. Line-transect analysis was used to estimate densities of the species involved, and attempts were made to consider shifts in yearly and seasonal distributions in the 3 years surveyed. There have been no comparable studies off the coasts of Oregon and Washington, although some are being conducted.

MMS expended its largest effort in the Alaska OCS region. Although cetaceans are abundant in Alaskan waters, relatively little was known about them before the MMS-sponsored studies. The Alaska region presents special problems for conducting surveys to determine seasonal distribution and abundance: much of the area is remote from bases of operation, weather conditions often are poor, and the winter day is short. Consequently, work in the Alaska region is very expensive and often difficult. Many of these surveys were done for operational purposes to meet the requirements of lease stipulations that seismic and other activities not be conducted when bowhead whales are present in the area.

The bowhead whale, which occurs in the northern Bering, Chukchi, and Beaufort seas, presented a special problem to MMS. It is a high-profile species in two ways. First, it is legally classified as an endangered species; when preparations were being made for the first Beaufort Sea lease sale, it was commonly believed that the population might have numbered less than 1,000. (The most recent point estimate of population size accepted by the Scientific Committee of the International Whaling Commission in 1991 is 7,500 (IWC, 1991).) Second, it is the subject of an important subsistence hunt by Alaskan Eskimos. Consequently, a large proportion of the cetacean inventory effort has been focused on the movement patterns of this species. Surveys were done to obtain data on timing and median depth of fall migrations, and variations relative to ice conditions (Ljungblad et al., 1988; Traecy, 1988).

Generally speaking, the ESP has not funded studies whose primary focus is the development of new techniques of study; this is seen as lying outside the MMS mandate. However, because of both the limitations and the high cost of aerial survey for gaining information about whales, MMS has made an exception to the general rule: it has aimed research at developing a means of tagging whales with a device that would be linked to satellite receivers. This effort has not yet proved completely successful. Methods for tracking large cetaceans were assessed in an MMS workshop (Montgomery, 1987). Such a satellite-linked radio tag would permit individual whales to be followed continuously, regardless of weather or day length, for extended periods and without using aircraft and human observers. Contracts were let to both the Woods Hole Oceanographic Institution (WHOI) (Watkins, 1981) and Oregon State University (Mate and Harvey, 1981, 1982) for the development of tags and systems to allow their attachment to whales. Although the species of greatest interest was the bowhead, development and testing involved more abundant and more accessible species, such as gray, humpback, right, and fin whales. The benefits of a satellite tag are great for understanding habitat-use and movement patterns. A fully operational tag has the potential to yield very important data on such subjects as critical habitat and the influence of offshore operations on

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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migration behavior. Studies were also undertaken to determine the effects of the attachment systems, all of which involved invasion of the skin, on the whales themselves. Work undertaken at WHOI included an attempt to assess the effects of implanted radios on the skin of fin whales that were to be taken in the Icelandic commercial whale fishery (as governed by regulations and quotas determined by the International Whaling Commission). Laboratory work was undertaken at the University of Guelph.

Surveys of the distribution and abundance of seals and sea otters in lease-sale areas have been funded by MMS in most regions of the Pacific coast, including Alaska, although some of these surveys are over 10 years old. Combined with data gathered by other agencies, and within reasonable limits, these surveys provide adequate stock assessments for some species (harbor seals, sea lions, fur seals, and sea otters). There is somewhat more recent information for ringed seals. More information is needed on at-sea distribution, movement patterns, feeding habits, and feeding areas for all species to monitor changes in population size. Several of these species have been undergoing dramatic population declines. The basic understanding has been summarized in a readily accessible publication (Lentfer, 1988).

A comprehensive polar-bear research program has been under way in the Fish and Wildlife Service since the 1970s, and so there was no need for MMS to duplicate such a program. MMS has, however, provided FWS with supplemental funding and logistics support (Cleve Cowles, Chief, Environmental Studies Unit, Alaska Regional Office, MMS, pers. commun., 1991). FWS has studied population size, movements, denning location and behavior, and production and survivorship of cubs (Amstrup et al., 1986). That information is adequate for impact assessment at the lease-sale stage.

FWS has also had an extensive program of research on manatees and has adopted a manatee recovery plan because of their status as an endangered species (FWS, 1989). Although manatees reside primarily in fresh water on coastal waterways in Florida, they come into salt water to forage on sea grass and to move seasonally from one coastal area to another. It is important for MMS to document use of marine habitat and foraging areas where oil could come ashore and where there is potential for collisions with boats and barges.

Surveys of marine mammal abundance are now being done in the entire outer continental shelf by NMFS as required by the MMPA for purposes of managing bycatch of marine mammals by fisheries. While these surveys will be useful to MMS, they do not address seasonal or overall distribution.

Effects

The relatively large size of most marine mammals and their protected status would make them poor experimental subjects, even if they became available for study. The primary concerns are related to the effects of spilled oil and to disturbance by underwater and airborne sound. Most of the research has been short-term research.

Direct Observation of Marine Mammals in the Presence of Oil

It has been possible to study cetaceans in the wild to observe their responses to oil slicks from spills and from natural seeps. During the CETAP project, Goodale (1981) observed both dolphins and baleen whales behaving apparently normally in slicks of crude oil that resulted from the sinking of the tanker Regal Sword off Cape Cod; some humpback and fin whales

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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seemed to be feeding in the slick. As part of MMS-sponsored research, Evans (1982) observed gray whales swimming through oil slicks from natural seeps off the California coast. Other researchers, not funded by MMS, have also observed dolphins in the presence of oil (Sorensen et al., 1984; Gruber, 1981). These observations indicate that cetaceans do not appear to avoid oil.

Very little work has been done on how pinnipeds and sea otters might respond behaviorally to the presence of oil. Sea otters are particularly vulnerable, because oil contamination soils their fur, destroying its insulating properties. Consequently, oiled sea otters often die from hypothermia or the toxic effects of oil that is ingested as they groom themselves. Even though the oil that is transported through Prince William Sound does not come from an OCS source, and MMS was not the primary agency responding to the Exxon Valdez spill, MMS responded quickly to provide some funding for studies that could take advantage of the opportunity it presented. Research efforts on sea otters were, however, managed by FWS, the agency responsible for sea otter management. Results of those studies will become available as legal restrictions permit.

Physiological Studies of Contact with Oil

Contact with oil might damage the skin, plug the nares, dog baleen, or possibly cause some other mechanical interference with affected animals' activities. For both legal and logistic reasons, it is impractical to expose whales to an experimental oil spill or to feed them oil experimentally. Geraci and St. Aubin (1980) examined the effects of oil on the flow of water through baleen taken from fin, gray, humpback, and sei whales, and Braithwaite (1983) investigated the effects on bowhead whale baleen. They found that the heaviest treatments of oil could impair filtering efficiency for a period of hours to a few days, but that the effects were reversible.

Geraci and St. Aubin (1982, 1985) found no apparent inflammation after exposure of small areas of skin of captive dolphins to crude oil and only slight inflammation after exposure to unleaded gasoline; reaction of the skin of human volunteers exposed to the same gasoline was greater. They also found no allergic contact dermatitis after repeated exposure to aromatic hydrocarbons; they reported little to moderate cellular damage after such exposure, but it was reversible. Although the most severe exposures (75 min of continuous contact) produced definite effects on dolphin skin, the effects were reversible and appeared to be no more severe than effects on the skin of other mammals. The most severe exposures exceeded those reasonably expected to result from a spill involving free-ranging animals that would be at the water's surface for only brief periods. The study concluded that the potential for severe effects of contact of cetacean skin with petroleum is much less than was commonly suspected earlier and that adverse effects may be temporary on species that do not rely on fur for insulation.

The ESP has funded work on the effects of oil on fur seals and sea otters. Both species rely on their thick fur to insulate them. When the fur becomes soiled with oil, it loses its insulating function, and many of the animals die of hypothermia. Costa and Kooyman (1981, 1982), Tetra Tech (1986), and Davis (1986) investigated the effects of oil on sea otters and their habitat and sought ways to rehabilitate such animals and return them to their environment. Their studies have generally shown that sea otters are extremely vulnerable to oil contamination, but that cleanup of individual animals is possible, if facilities and trained personnel are available. The ability of cleaned and rehabilitated otters to survive in the wild is uncertain.

Studies in Canada by Geraci and Smith (1976) suggested that the thermoregulatory

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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effect of oil on ringed seals was not as great as on animals that depend on their coats for insulation. Those results would probably be the same in other seals that do not use their fur as major protection against hypothermia and in sea otters with respect to damage to internal organs. Similar studies done with captive seals resulted in death of the animals, possibly because of the added stress of captivity (Smith and Geraci, 1975), indicating that the effect of spills may depend in part on other variables, such as the time of year, that affect the general condition of the animals at the time of the spill.

Geraci and St. Aubin (1982) reviewed the literature on ingestion of petroleum by other mammals and concluded that it is unlikely that any cetacean would ingest enough spilled oil to cause its death. Because the light fractions of petroleum would rapidly evaporate and would be carried away from the area of an oil spill, they concluded that exposure to petroleum vapors was not a likely potential cause of harm to cetaceans from an oil spill.

As the following quotation from Geraci and St. Aubin (1987) suggests, there has been little experimental study of the relative toxicity of ingested oils on marine mammals:

There have been three oil ingestion experiments in seals and one in cetaceans. Harp seals given a single dose of up to 75 ml (1-3 ml/kg) of crude oil began to excrete oil in the feces within 1.5 h, suggesting increased gastrointestinal motility (Geraci and Smith, 1976). Some was undoubtedly absorbed into blood and tissues, as was shown in studies of ringed seals given smaller doses (0.2 ml/kg/day for 5 days) of oil (Engelhardt et al., 1977; Engelhardt, 1981). There was no gross, microscopic, or biochemical evidence of tissue damage in either species. A bottlenose dolphin given small quantities (2.5-5 ml) of machine oil daily for over three months also showed no clinical signs of organ damage or intoxication (Caldwell and Caldwell, 1982).

The discovery after the Exxon Valdez oil spill that several killer whales were missing from pods in Prince William Sound raises questions about the effects of oil on cetaceans (Trustee Council for the Exxon Valdez Natural Resource Damage Assessment, 1991) and suggests the need for tissue sampling following oil spills. At the time of writing, the recent data on Prince William Sound killer whales are being kept confidential, pending possible litigation. When these data become available, it will be possible to better evaluate and clarify the potential explanations.

The only research conducted on oil effects on polar bears was an experiment involving three bears in Canada near Churchill, Manitoba (Engelhardt, 1981; Oritsland et al., 1981; Hurst and Oritsland, 1982). The bears were forced into an oil-covered pool and suffered hypothermia and various toxic effects. Two of the bears died as a result of toxic effects of oil, and the other survived only after an intensive and prolonged period of treatment. There has also been one documented case of a polar bear dying after consuming ethylene glycol (antifreeze) (Amstrup et al., 1989). There does not appear to be a need for MMS to fund additional research on effects of oil on polar bears.

MMS has sponsored research on the effects of oil on sea otters. It included behavior of captive animals exposed to slicks (Siniff et al., 1982), thermoregulatory effects (e.g., Costa and Kooyman, 1981, 1982), and cleaning and rehabilitation of the otters (Davis et al., 1988; Williams et al., 1988). Others have studied oil and otters, both experimentally and opportunistically. The value of rehabilitating otters and releasing them to the wild is controversial, because the process of rehabilitation is expensive, the number of animals that can be treated is small, and the survivorship of animals that are rehabilitated and released appears poor (Monnett et al., 1990).

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Almost nothing is known about the effects of oil contamination on manatees. It is possible that oil ingested with food could affect the microflora in the animals' digestive tract essential for digesting cellulose. Barge and boat traffic is extensive in the inland and coastal waterways of Florida where manatees live, so the animals are chronically exposed to low concentrations of petroleum. However, there are no studies of effects.

Geraci and St. Aubin (1990) and Richardson et al. (1989) have summarized the results of research sponsored by MMS and others on the effects of oil on marine mammals.

Sources and Characteristics of Underwater Sound

Over the last few decades it has come to be recognized that marine mammals live in an environment greatly affected by sound. Sound travels much farther in water than light does and it can be detected in the dark. Marine mammals make great use of underwater sound for various purposes and at various frequencies. Baleen whales use sound for communication and probably for obtaining information from their environment; toothed whales use sound for echolocation as well. Because offshore petroleum operations involve activities that produce underwater sound, there is a potential for them to interfere with sound produced by cetaceans as well as to cause disturbance and stress. Even as recently as 1980, there was very little information about the frequency composition and intensity of underwater sound produced by such petroleum-related activities as drilling, dredging, and vessel traffic or the intense sound produced during seismic exploration. And there was almost no information about the efficiency of sound transmission through water. MMS has invested considerable effort in research on the characteristics and effects of underwater sound.

Gales (1982) studied the underwater sound from oil-production platforms in Santa Barbara Channel, California, and in Cook Inlet, Alaska. Greene (1987) studied the sounds produced by dredges, drilling operations, and vessel traffic in the Canadian Beaufort Sea. The sounds produced by those operations tended to be of low frequency; the majority was below 500 Hz. Helicopters and, to a much smaller extent, fixed-wing aircraft are also used in offshore petroleum operations; they also tend to produce sound mostly below 500 Hz. The energy impulses used for seismic profiling are produced by nonexplosive means, such as with air guns that release pulses of compressed air. Greene (1982) found, for example, peak sound pressures of 242-252 dB 1 meter from the source. Seismic sounds are by far the most intense sounds produced by the petroleum industry; under some conditions, they can be detected up to 100 km away.

The transmission of sound underwater is complex and depends on a number of factors, including water temperature, salinity, depth, the presence of ice, ambient noise, and the nature of the sea bottom. Because of the complexity, simple general equations are unreliable predictors of sound propagation, and so empirical observations in each location of interest are necessary. Greene (1987) and Miles et al. (1987) have derived empirical equations for the attenuation of sound with distance at particular locations in the Canadian and Alaskan Beaufort Sea. The distance over which sounds are detectable depends not only on the intensity and the rate of transmission loss, but also on ambient (background) noise and hearing ability. Ambient noise arises primarily from wind and storms, ice movement, biological sources, and shipping activity. Some effort has been expended in measuring the natural ambient sound in the Beaufort Sea (Greene, 1987; Miles et al., 1987).

Assessing the potential effects of industrial noise on whales depends not only on the nature of industrial sounds, but also on the nature of the sounds made by the whales themselves. Consequently, a large number of recordings of bowhead sounds have been made by Greene

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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(1987), Wursig et al. (1985), and Ljungblad et al. (1987). Their calls typically can be described as moans, groans, growls, and trumpetlike sounds. The frequencies of most bowhead sounds are below 1,000 Hz, although some are up to 2,000 Hz. Data on various factors related to noise produced by OCS activity, sound transmission in water, ambient sounds and sounds made by the whales themselves, and disturbance responses can be combined to define a “zone of influence” in which marine mammals can be affected by noise. Although these zones cannot be precisely estimated because of limitations in available data and the necessity of relying on assumptions, the attempt to do so is a useful way to discover data gaps (Richardson et al., 1989; Davis et al., 1990).

Effects of Underwater Noise and Disturbance

Sound sources in the water can be characterized as moving (i.e., vessels), stationary (i.e., dredging and drilling operations), aircraft, and seismic. MMS played an important role in funding research on the effects of underwater sound on cetaceans. Many of the points covered were identified in an Acoustical Society of America workshop held in 1981 (ASA, 1981). Information on the response of whales to underwater sound and disturbance is derived from two basic types of situations. First, it has been possible on many occasions to observe bowhead whales close to various industry operations; but opportunistic observations lack controls for comparison. Second, experimental observations have been possible under more controlled circumstances; these have sometimes involved playback of recorded sounds and sometimes full-scale operations that have been under control of scientists conducting the work. MMS studies have focused on baleen whales, in particular bowheads (e.g., Richardson, 1985; Richardson et al., 1991) and to a lesser extent gray whales (Malme et al., 1983). A species of toothed whale, the white whale, has also been the subject of one study (Stewart et al., 1983).

Bowhead whales were the primary species of concern in the Alaskan Beaufort Sea, an area that was considered particularly likely to yield oil and gas, owing to its proximity to the supergiant Prudhoe Bay oilfield. As an early step to understanding the problem that might be presented by underwater sound, the U.S. Naval Ocean Systems Center (NOSC) recorded sounds produced by production platforms of various sorts in several areas and collected observations of whales made by persons working on the platforms (Gales, 1982). The NOSC analysis included sound intensity and frequency. LGL Limited (Richardson, 1985) began a study in 1980 of bowhead whales in the Canadian Beaufort Sea, the summer feeding grounds, where offshore exploration had been under way (outside the Mackenzie River estuary) since 1976. The largest and most extensive study of the response of whales to disturbance was conducted from 1980 to 1984 in the Canadian Beaufort Sea (Richardson, 1985) with additional work in the Alaskan Beaufort Sea (Ljungblad et al., 1987). The clearest response of bowhead whales to an industry activity was the response to vessel traffic. Obvious responses usually began when a vessel approached within 1-4 km of the whales. MMS also funded studies that defined zones of influence of activities on cetaceans (Richardson et al., 1989, 1991; Davis et al., 1990).

Beginning in 1978, NOSC began studies of bowheads in Alaskan waters, primarily the Beaufort Sea. The main aim was to study the timing and location of bowhead movements in spring (April, May, and early June) and fall (late August, September, and October). In some years, responses to seismic exploration were also studied. These studies were intended to be used for determining whether the bowheads' migration corridor was displaced offshore by industry activity. However, it is not clear that the data have been appropriately analyzed in this context.

The communication of baleen whales is probably more susceptible to interference from

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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OCS activity than that of other whales because the dominant frequencies in their calls overlap with the dominant frequencies of industrial sounds (Davis et al., 1990). However, the importance of such effects cannot be determined until there are data on the hearing ability of baleen whales.

In general, ship traffic and aircraft overflights can cause short-term behavioral reactions and temporary local displacement of some marine mammals. Elevated noise levels might mask natural sounds that marine mammals rely on, and there might be a long-term reduction in utilization of heavily disturbed areas by some species (Davis et al., 1990).

Ecological Processes
Population Ecology

The research necessary to estimate and monitor the vital characteristics of the population ecology of marine mammals within a geographical area with sufficient precision to be useful requires a long-term commitment of funds. For high-profile species, especially those which are particularly vulnerable, data of this nature are required, if population modeling and analysis have a high priority. North Pacific fur seals and California sea otters are examples. Where possible and appropriate, MMS should focus on species, populations, life history parameters, and locations that could serve as indicators, i.e., be of most use for extrapolation with careful validation.

We believe that studies of the population ecology of marine mammals in areas that might be affected by development are appropriate. However, we caution against overreliance on such studies as a basis for monitoring effects, although they could provide information that is essential for assessing potential impacts and population-recovery times. The dynamics of marine-mammal populations are affected by many factors; even if the populations could be monitored precisely enough to detect important changes, it might be very difficult to know whether the underlying causes are related to petroleum development. We recommend that population monitoring studies include an attempt to identify causal linkages, to ensure that clearest indicators of effect are studied.

Modeling of Interactions Between Oil Spills and Marine Mammals

The environmental studies program has recently funded modeling efforts that have attempted to explore the effects of oil spills and other petroleum-related activities on various marine-mammal populations. Reed et al. (1986) summarized existing data on northern fur seals into a model for studying the potential effects of oil spills in the Bering Sea on the population dynamics of this species. Their study used data on migration routes and other population characteristics to explore what would happen if oil contamination existed in particular areas of the Bering Sea at different seasons. The study was useful in pointing to the need for additional data if such modeling efforts are to be more predictive. Siniff and Ralls (1988) performed a 2-year field study on California sea otters and obtained population and movement data. Their data were added to existing data to construct a population model to help in predicting the effect of oil spills along the California coast. That study, too, was valuable in helping to predict times for the population to recover from oil spills of different sizes and in different regions of the California coast. It also pointed to the need for additional information to support predictive

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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modeling: data on population characteristics, such as survival of sex and age classes, changes in reproductive rates from one year to the next, and the variance of various population measures.

Applied Science Associates undertook a computerized simulation study aimed at integrating information on the location and timing of the migration of bowhead and gray whales with oil-spill trajectory models to arrive at the probability of interaction between oil spills and these species (Reed et al., 1987). The usefulness of models of this sort is limited by their inability to incorporate microscale behavior of oil and the response of whales to oil. Thus, the models might provide a reasonable picture of the potential for whales to be in the proximity of oil, but not of the degree to which there will be contact.

Trophic Studies

Trophic studies have been done in both the Alaskan and Canadian Beaufort seas to determine if changes in abundance of bowhead whales are correlated with changes in oceanographic conditions, and productivity. Griffiths and Buchanan (1982) found that changes in distribution of bowhead whales were related to oceanographic conditions. Richardson (1987) found that the changes were related to food availability caused by the presence or absence of upwelling. Thomson (1984) examined feeding patterns of gray whales in the Bering Strait area. A study of pinnipeds in the Bering and Chukchi seas analyzed stomach contents of seals to understand how the animals function ecologically (Lowry et al., 1981a,b). A current study, the South Channel Ocean Productivity Experiment (SCOPEX), cofunded by MMS and NSF, is examining the relationships among right whales, zooplankton, and the physical and biological environment. The study is based on oceanographic sampling, whale tagging, and aerial surveys conducted in the Great South Channel where humpback whales congregate at particular times of year.

Studies of trophic relations and food availability, conducted over a period of several years, should help provide understanding of spatial and temporal variability in the distributions of marine mammals.

Gaps in Available Data
Inventory

The results of MMS studies have formed a general picture of seasonal and geographic variation and of the use of particular areas by cetaceans in most OCS waters. Exceptions are the South Atlantic, the Gulf of Mexico, and off Washington and Oregon, although surveys are under way in the latter two areas. The information base could be improved with considerable effort as has been expended for the bowhead whale, although we question whether the need for the large bowhead effort has been justified scientifically. These studies were driven primarily by legal and political pressures that have been present because of the requirements of the ESA and MMPA, and the importance of bowhead whales as a subsistence resource for Alaskan natives.

More detailed and intensive study of whales is justified in specific areas proposed for development after exploration has determined that commercial quantities of petroleum are present. Such research should aim to determine the numbers of animals using an area, movement patterns, and the ecological function of the area (e.g., feeding, migration, etc.). In studies that focus on a relatively circumscribed area, research might include vessel-based

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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observation incorporating identification of individual animals, as well as aerial surveys. The use of satellite tags is potentially valuable here (Mate, 1989, 1991).

Information on pinniped and sea otter distribution and abundance in several OCS areas is lacking. Particularly lacking on the U.S. east coast are MMS-funded projects that consider distribution and abundance of harbor seals and gray seals; as mentioned earlier, some information has been collected by other government agencies or through private funding, but additional MMS effort is needed to provide a historical record of changes in their population. Available information (Gilbert et al., 1979) suggests that gray seals are increasing in some regions of the northeastern coast. The role of gray seals in the ecosystem is virtually unknown, and monitoring the increase in their abundance would be valuable for correlation with future changes in ecosystem structure and function. Otherwise, if changes in abundance accompany oil and gas development, it will be difficult to separate the influence of development from unrelated causes of change. If extensive exploration or development is planned near seal habitat, MMS should undertake studies of seals.

Surveys have been done along the Pacific coast in California; in some locations along the Alaska Peninsula, particularly in the Cold Bay-False Pass region; and in some locations of the Bering Sea and are going on in Oregon and Washington. Ice seals have been surveyed along the northern coast of Alaska. Those areas are important with respect to oil and gas leasing programs.

Although there has been much oil-related development in Prince William Sound, little research has been done there; however, oil that is transported through Prince William Sound comes from onshore locations near Prudhoe Bay, and not from OCS areas that would fall within MMS 's responsibility. Because of the pipeline terminus and the importance of the region with respect to transport of oil, some long-term studies of cetaceans, pinnipeds, and sea otters are appropriate. The Fish and Wildlife Service has conducted long-term sea otter studies in the region, so the general population status of this species is well known. However, data on cetaceans and pinnipeds of the Prince William Sound region are sparse, although some seasonal surveys have been made. Because this area seems to be at high risk, basic inventory and process studies on all marine mammals would also be appropriate. Although there is some question about which agencies should assume responsibility, MMS should continue to take part in these studies, as it did after the Exxon Valdez spill, because of the opportunities to examine actual effects of spills and because of the importance of the region for the transport of oil.

The need for further information on distribution and abundance of pinnipeds and sea otters will depend in large part on future leasing plans and discoveries that could lead to development. Information on distribution and abundance is one of the first items necessary, in light of legal requirements with respect to leasing programs. Data on distribution and abundance in most locations are largely insufficient for documenting normal annual variations. Therefore, the effects of oil and gas development on a given region are impossible to document, because they might be well within the range of variation caused by other environmental factors. That suggests that monitoring studies should take into account mechanisms of potential impact. Distribution and abundance data have been collected over just a few seasons before leasing programs have begun. Lessons from prior studies point to the need for longer-term data in regions where oil and gas development is likely to occur but before development occurs.

Effects

The effects of oil and gas exploration and extraction have been considered in the

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Environmental Studies Program. The effort has centered mostly on the noise generated in these processes. Kelly et al. (1986) considered the effect of noise disturbance from on-ice seismic exploration on ringed seals, as did an earlier study by Cummings et al. (1984). Those studies considered whether the noise produced by oil and gas exploration and extraction have important impacts. In general, the studies have shown that the noise impacts are localized and not likely to have large population consequences. Similar studies by Riedman (1983) considered the effects of marine seismic noise on sea otters in California and came to a similar conclusion. As mentioned previously, modeling efforts on the effects of OCS activities on marine mammals have been useful in pointing to the need for additional data as described below.

Considerable information has been obtained on the effects of oil contamination on the two most sensitive species: sea otters and fur seals. These studies have generally shown that rehabilitation of the two species after oiling is possible, but have pointed to the need for extensive facilities where rehabilitation programs can be executed.

It seems likely that the information obtained from the earlier Canadian studies on ringed seals can be transferred to other pinniped species that do not rely on fur for protection from hypothermia. A recent review by Geraci and St. Aubin (1990) is a valuable resource with respect to gaps in data on the various species of marine mammals. It seems that many data on effects can be transferred from one species to another for which insulation by fur is not a problem.

The California sea otter has been designated as threatened under the ESA because of its small population size and the increased risk of spills from tankers carrying oil. As described above, Siniff and Ralls (1988) pointed to the need for additional information on population characteristics such as survival of various sex and age classes, changes in reproduction rates from year to year, and a sense of the variance of the various population characteristics from one year to the next.

Ecological Processes

Little work has been done in process studies on pinnipeds. Information on trophic relationships of some of the northern species is available from collections from previous MMS studies (Lowry et al., 1981a,b). However, further information on ecosystem processes—knowledge of major foraging areas, seasonal variation in prey species, potential areas of competition between pinniped species for food, and general knowledge of various population characteristics—is virtually lacking for most pinniped species, on both the east and the west coasts of the United States. Information on feeding areas of the northern sea lion is becoming available through studies of its decline and its apparent interactions with fisheries of the high seas and coastal areas.

The information on walruses and sea otters with respect to trophic interaction and food-web relationships is much better. A recent monograph by Riedman and Estes (1990) reviews sea otter behavior, ecology, and natural history. Estes and Jameson (1983) have provided detailed information on the relationship between sea otter populations and the nearshore community. Data are still lacking that could tie changes in population characteristics—reproductive rates, survival rates, amount of time spent foraging, and sex-age interactions—with the structure and function of the nearshore community. Recently, Siniff and Ralls (1988) have provided some insight into the relationship between these characteristics and the animals' population status in California. However, data on sea otter populations at different locations in Alaska are lacking. The feedback mechanisms between prey abundance and walrus population are not well understood.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Conclusions and Recommendations
Inventory

MMS has funded comprehensive surveys of marine mammals, particularly cetaceans. The information that has been gathered on seasonal patterns of use of most U.S. waters by marine mammals has provided an understanding that is generally adequate for assessment of the potential for damage from OCS activities, but not as the basis for assessing change (including the measurement of impacts of actual events). Additional site-specific information will be needed for the latter purpose.

The surveys of bowhead whales in the Beaufort and Chukchi seas have been extensive and prolonged. Bowhead whales have received uniquely thorough study because, in addition to legal requirements, the entire Alaskan range of this species is scheduled for oil and gas leasing, because it is an endangered species, and because it is the object of a very important subsistence hunt by Alaskan Eskimos. In view of the present, much-improved understanding, MMS should re-examine the need for continuing the high level of attention that the bowhead receives; MMS should convene a workshop of experts on bowhead whales to examine the need for further bowhead research and to consider the possible value and design of site-specific and population monitoring.

There has been controversy over the median depth analysis (an analysis based on the median depth of water in which bowhead whales are observed) that has been standard for the bowhead fall-migration data. Reanalysis of the data based on different criteria seems appropriate. Reanalysis could be initiated through a small workshop in which biases in past analyses could be discussed and improved procedures identified, e.g., sensitivity analysis.

Information on seasonal distribution and abundance of marine mammals in the Gulf of Mexico and South Atlantic regions is incomplete at present. In those regions, additional surveys are needed, focusing particularly on patterns through the entire annual cycle. This is particularly important, because of the current degree of exploration, development, and production in parts of the regions.

Effects

The bulk of the existing information on the behavioral responses of cetaceans to noise and disturbance from offshore petroleum operations is derived from studies funded by MMS. In addition, to support the disturbance studies, much research was conducted on the nature and transmission of underwater sound produced by petroleum operations. Those studies have yielded a good understanding of the types of responses exhibited by cetaceans and the distances over which the responses occur.

One need is for an investigation of the behavioral phenomenon of habituation (i.e., the diminution of response of an animal after repeated exposure to harmless stimuli, such as noise from aircraft flights or nearby vessel traffic). Many wild animals commonly show a great deal of tolerance to human activity, e.g., birds nesting and feeding near active aircraft runways and busy highways. It would be useful to understand better how the ability to habituate might affect the long-term responses of marine mammals (and birds) to effects of OCS development. It is also possible that diminution of response is a product of physiological stress (e.g., adrenal depletion) rather than habituation, and this hypothesis needs to be tested. To determine the significance of individual noise sources in masking the sounds made by marine mammals, it would be useful to

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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better understand the functions and significance of the sounds that marine mammals make. Data on the hearing ability of some species, particularly baleen whales, would also be useful, although perhaps difficult to obtain (Davis et al, 1990).

After an oil spill, much effort is expended on rehabilitation of oiled animals. That effort is extremely expensive. In the case of sea otters in Prince William Sound, probably only a small fraction of the animals contaminated with oil were captured and treated (Trustee Council for the Exxon Valdez Natural Resource Damage Assessment, 1991), and many of the animals captured died either in captivity or shortly after release. The rehabilitation effort had little effect on recovery of the Prince William Sound sea otter population. Rehabilitation operations exist for humane reasons, but are unlikely to increase population size or health in a manner that will increase recovery rates. That might not be true of small populations, and in instances where the animals affected represent a large proportion of an endangered population, but the population size at which rehabilitation is effective in enhancing recovery remains to be determined. Rehabilitation of marine mammals (and birds) needs to be examined in a population context. Considerable review of and planning for sea otter rehabilitation have been done by FWS and California as part of their effort to translocate southern sea otters to San Nicolas Island (FWS/California Department of Fish and Game, 1989). Workshops focusing on the matter are appropriate, particularly before MMS spends much money on rehabilitation centers and other facilities. Such a workshop might also examine this question in relation to marine birds.

The question that always arises after oil contamination has affected populations and ecosystems is the length of time needed for recovery. Recovery of ecosystems involving marine mammals is complicated, and rates of recovery are often difficult to predict, because of the lack of information on density-dependent responses and trophic relationships. Studies to gain information for assessing recovery in areas where oil or mineral development has occurred are appropriate. Such recovery depends on local circumstances. For example, are animals from surrounding areas available for colonization? Is the whole population, or some fraction, likely to be affected? Estimates of local survival rates, reproductive rates, and other population characteristics before any spill or other environmental event will be necessary, if recovery times are to be predicted. The exact nature of studies and data needed for such considerations are tied to local situations and the species of marine mammals involved.

Many OCS activities on the north coast of Alaska might take place in winter months and could have effects that are specific to polar bears. In the winter months, female polar bears producing cubs retire to dens, while others are active on the ice. Potential effects and specific research needs were identified in a January 1989 workshop sponsored by the Marine Mammal Commission. Research needs identified by the workshop include the identification of denning habitat and ways to reduce human interactions with polar bears (Lentfer, 1990). Those recommendations should be considered and evaluated in planning studies for polar bears.

MMS has sponsored a relatively complete suite of studies on the effects of oil on whales, sea otters, and fur seals and on rehabilitation of oiled sea otters; studies on the effects of oil on hair seals have been conducted by other researchers. Although some questions remain, legal and permit constraints and public opinion prevent additional experimental work.

MMS should be prepared to study the effects of oil on marine mammals when oil spills present the opportunity. We recommend that MMS enter into agreements with the appropriate agencies—i.e., FWS and NMFS and state agencies—regarding the necessary protocols and contracting procedures so that the research possibilities presented by “spills of opportunity” are not lost.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Ecological Processes

MMS's efforts on distribution and abundance have yielded information on the species and numbers of marine mammals that might be present at a particular location at some time, but not basic details of population dynamics or data on diet and habitat that would be necessary to determine indirect (e.g., food-chain) effects. The exception to that generalization has been related to sea otters in California. For key species, it is appropriate to collect basic data to document and understand causes of trends in populations and to predict recovery times in the event of a major impact. However, we recognize that the necessary effort will not be possible for all species or all areas. For example, long-term data on harbor seals and northern sea lions in the Prince William Sound area before the Exxon Valdez spill are minimal. Some survey data are available from MMS contracts with the Alaska Department of Fish and Game and other sources, but they are sparse. Data on characteristics such as reproductive rates, survival rates of young during lactation, and survival through the first year of life are all needed and would have been useful for comparison with estimates after the Exxon Valdez spill.

MMS should consider studies to obtain estimates of population measures in areas and for species most likely to be affected by OCS oil development and associated activities. The northern sea Lion, the northern fur seal, and the harbor seal (in some areas) are declining in abundance and should be considered for such studies. Harbor seals are considered to be nonmigratory, so their populations could be affected substantially; studies of this species in areas where oil development has occurred or is likely to occur would be appropriate.

An understanding of the underlying factors that govern the distribution and ecological relationships of key species is important for assessing the potential for impact and for distinguishing natural changes from those anthropogenic changes. Process studies should collect information on food and feeding behavior and the factors that control food distribution. A general knowledge of processes is necessary at the leasing and exploration phase, but we do not believe that it is necessary for MMS to conduct detailed site-specific studies that are not related to general process questions until there is a discovery that could lead to development and production. There might, however, be cases where the concern or extent of activity is so great as to justify a more complete range of studies than would normally be considered appropriate, such as the cases of the bowhead whale and California sea otter.

Data Management and Accessibility

The data collected by MMS-funded researchers are of Little use if they cannot be accessed. Data management can take several useful forms in addition to making final reports available: archiving original data, placing data in an interactive computer format, preparing papers for publication in refereed journals, and publishing books. MMS has increasingly recognized the importance of publishing the results of research, and has supported it, but there is room for improvement, particularly with respect to older work. Private contractors, in particular, need to be funded to permit them to publish and make data more widely accessible. Otherwise, financial pressures can make these activities difficult.

BENTHIC STUDIES

The Minerals Management Service and the Bureau of Land Management before it have

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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spent over $128 million from 1974 to 1988 in the Environmental Studies Program for studies of the benthic environment. The studies have included analysis of the benthic fauna and physical and chemical characteristics of the habitats of interest for OCS development (See Table 3-1, Table 3-2, Table 3-3, Table 3-4 and Table 3-5). Under authority of the Outer Continental Shelf Lands Act (Section 20), the ESP has the responsibility of providing an adequate description of each environment before leasing regions of the OCS for oil and gas exploration and development and of monitoring the environment during these activities to document environmental impacts. Studies of benthic organisms have been seen as key elements of both preleasing descriptions and monitoring, because these organisms are thought to be relatively susceptible to contaminants that settle to the seabed and because their relatively stable populations and sessile nature would make them suitable for impact assessment.

Accomplishments of the Environmental Studies Program

The panel assessed the benthic programs supported by the ESP and evaluated their contributions to advances in marine benthic ecology and predictions of the impacts of OCS operational activities. The effects of some OCS activities, such as the discharge of drilling fluids and accidental oil spills, and the long-term effects of offshore oil and gas development have been reviewed extensively by previous groups (NRC, 1983, 1985; Boesch and Rabalais, 1987). More recent studies (e.g., Neff et al., 1989; Chapman et al., 1991) have added to our knowledge, but they have not changed the overall picture. Therefore, the panel limited itself to reviewing the findings of previous reports, examining ESP case histories, and developing conclusions and recommendations for future studies.

One of the major achievements of the ESP in regard to benthic studies was the characterization of benthic habitats of the U.S. continental shelves. In most instances, however, sites were sampled only infrequently or for too short a period, so there is little understanding of temporal and spatial variability. As discussed by Rabalais and Boesch (1987), benthic surveys of the OCS revealed highly diverse oceanographic and biological conditions. Marine ecosystems are complex, open, and dynamic (Boesch et al., 1987), and interpretation of the environmental effects of anthropogenic activities is therefore extremely difficult. Temporal and spatial variation occurs at all levels of the ecosystem, and predictable patterns of resilience and recovery from perturbations are difficult to discern.

Descriptions of the dominant features and processes of the continental shelf environments of the United States constitute an adequate basis for defining research efforts directed at understanding the processes governing shelf environments and evaluating the impacts of environmental perturbations. The continental shelf environments of the United States range over 48° latitude and extend from polar seas to nearly tropical waters. The continental shelf regions of the United States discussed by Rabalais and Boesch (1987) are presented in Table 3-6 with MMS's planning regions for comparison.

Each of the regions is characterized by rather distinct oceanographic, geological, and biological characteristics. Because the biological systems usually reflect the physical forces and the geological substrata, it is critical that the abiotic characteristics of each region be understood. The dominant physical oceanographic features of U.S. continental shelves were discussed in an earlier report on physical oceanography (NRC, 1990a), and the biotic and abiotic features of these environments were discussed in detail by Rabalais and Boesch (1987). Those works make it clear that much is known about the geological and biological characteristics of each of the shelf environments.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

TABLE 3-1 Features and Processes of U.S. Continental Shelf Areas—Shelf Morphology, Sedimentary Regimes, and Depocenters

Region

Shelf morphology

Stage of sedimentary evolution

Sedimentary regime

Depocenters

New England

Dominated by shallow plateau (Georges Bank) bordered by deeper channels; Gulf of Maine with irregular bedrock and basins; large sand shoals and waves of Nantucket Shoals; shelf edge incised by submarine canyons

Autochthonous

Low depositional, dominantly sands with gravels in areas, sand shoals and waves in shallower areas, grade to medium to fine sands mid shelf

Major area SW of Georges Bank, “Mud Patch,” heads of submarine canyons, some eventually to Long Island Sound

Middle Atlantic Bight

Broad, gently sloping platform with complex mesoscale topography of ridges and smaller sand waves, sediment-filled channels

Autochthonous

Low depositional, dominantly sands >75%, mostly >90%, fine-grained sediments generally absent except for some accumulation in depressions

Deposited in salt marshes and estuaries or carried to shelf edge, slope, and heads of submarine canyons

South Atlantic Bight

Broad, gently sloping platform with cross-shelf shoals, sand waves, rocky outcrops; calcareous reefs at shelf break; no submarine canyons

Autochthonous

Low depositional, coarse to medium sands with finer sands at depth, little fine fraction except in cape-associated “shadows”

Deposited in marshes and estuaries or carried to shelf edge

West Florida Shelf

Broad, gently sloping platform of carbonate sand sheet with subsurface or low relief exposed hard strata at mid and outer shelf and algal nodule areas at shelf break

Autochthonous

Predominantly sands with little fine fraction, some areas of finer sediments nearshore, mid shelf and near Florida Keys

Off shelf and into Florida current, may be removed from shelf area

North Central Gulf of Mexico

Broad, gently sloping shelf except at Mississippi River prodelta and De Soto Canyon; ridges and pinnacles on outer shelf and at shelf break

Autochthonous/Allochthonous

Quartz sand sheet with increasing fine fraction towards Mississippi River prodelta and off major estuaries

Mississippi River prodelta, sound, off Mobile Bay, also to outer shelf of West Florida shelf

Northwestern Gulf of Mexico

Gently sloping, wide shelf with relict shorelines, distributary ridges, relict reefs and numerous diapirs on shelf, shelf break and slope; very wide, hummocky slope

Allochthonous/Climax Grading

Sand decreases and silt increases seaward; patchy occurrence of sand areas, increase in clay W of delta, poorly to very poorly sorted sediments inshore

Mississippi and Atchafalaya deltas and prodeltas, outer shelf and slope

South Texas

Gently sloping wide shelf with deltaic bulges at Rio Grande and off Matagorda Island with broad, ramp-like indentation between; relict shorelines and reefs, sediment-filled channels, diapirs on shelf

Climax Grading

Mostly silty sands with decrease in sand and increase in silt offshore, patches of sands on ancient deltas, higher clay content in area mid shelf off Port Aransas

Bays, outer shelf and slope

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

Southern California

Narrow shelf, complex borderland with southeast-northwest trending ridges and basins, shallow rocky banks at shelf edge, indentation by submarine canyons

Climax Grading

Progrades from sands to silty sands to sandy silts and then silts at shelf edge, more complex sediments around rock outcrops

Deposition mostly in nearshore basins and on slopes but also in outer basins

Central and Northern California

Narrow, gradually sloping shelf incised by several submarine canyons along entire length, bands of bedrock habitats on inner shelf, rock outcrops on outer edge of basins at shelf edge

Climax Grading/Allochthonous

Coarser, sandy sediments nearshore to finer silts and clays offshore, fine sediments between Eel and Klamath Rivers and off Russian River

Submarine canyons and slopes

Washington-Oregon

Narrow, gradually sloping and generally featureless shelf, some major submarine canyons incise shelf

Climax Grading/Allochthonous

Inner shelf sands to 60 m, mid-shelf silts to 120 m, some sandy near canyons

Mid-shelf sediments of silt similar to Columbia River suspended load

Bering Sea

Broad (>500 km), gently sloping marginal shelf in SE to broad, shallow epicontinental shelf in NE; relatively flat and featureless in SE, undulating hummocky in W, modern and relict sand ridges and shoals in NE, prograding Yukon delta in Norton Sound

Climax Grading, SE; Autochthonous, N; Allochthonous, Norton Sound

Fine-grained transgressive sands with decrease in sands offshore in SE; glacial gravel and transgressive sands in W; thin transgressive sands facies in N, nondepositional; thick, muddy deposits in Norton Sound

Major center in southern Chukchi Sea for Yukon-derived sediments, also eastern sector of Norton Sound, localized areas on southeastern shelf

Alaskan Arctic

Broad, gently sloping marginal shelf in Chukchi Sea to very narrow shelf in Beaufort Sea; little bathymetric relief except for Barrow Sea Valley and Hanna Shoal in Chukchi Sea

Climax Grading

Majority of Chukchi Shelf with 5ϕ sediments; Beaufort shelf with primarily sandy muds and silt and clay at shelf edge, gravels at shelf break, some input from river run-off, tundra slumping, and river ice

Low sediment transport nearshore and predominantly westward, possible depositional site in SW Harrison Bay for Colville River delta muds

Gulf of Alaska

Broad, gently sloping marginal shelf, dynamic bedforms of sand waves (8 to 15 m high); major submarine valleys and basins in NE, series of flat banks (50 to 100m) and troughs down to 200 m off Kodiak

Autochthonous/Climax Grading

Mostly reworked glacial off Kodiak, shelly sands nearshore, coarse sediments on banks, fine in troughs; silts/clays and high sedimentation rates inshore in NE, sand and gravel mixed with silts and clays at shelf break

Troughs off Kodiak (except Stevenson), volcanic ash as indicator of present day dispersal patterns; removed from shelf and slope in NE

Source: Adapted from Rabalais and Boesch, 1987.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

TABLE 3-2 Tidal and Wave Climates, Physical Processes and Benthic Boundary Layer Dynamics

Region

Tides

Wave climate

Dominant processes and events

Benthic boundary layer dynamics

New England

Semidiurnal of moderate magnitude, 4 m at mouth of Bay of Fundy; tidal current 30-40 cm/s in channels, >55 cm/s on Georges Bank proper

30-40% of waves >1.5 m, 50% of waves > 1 m

Constant reworking by fast tidal currents and waves down to 60 m, winter storms

Surficial sediments under almost constant scour, dynamic sand waves, low suspended particles over Georges Bank, 750-800 µg/l over mid shelf, 250 µ/l over outer shelf

Middle Atlantic Bight

Semidiurnal of moderate magnitude; tidal current <25 cm/s

~30% of waves >1.5 m, ~5-10% of waves >3.5 m

Wind-influenced currents on inner shelf, storm-wave generated currents affect outer shelf, winter storms

Ripple marks down to 200 m, winter storms main cause of disturbance >60 m, more frequent disturbance <60 m by winds and tidal currents; sand waves not active

South Atlantic Bight

Semidiurnal of moderate magnitude; tidal current <25 cm/s

Nearshore waves <0.5 m, ~20% of waves >1.5 m, ~5% of waves >3.5 m

Tidal currents and wind regimes affect depths to 20 m, freshwater inflow off Georgia and S. Carolina, hurricanes, Gulf Stream intrusions

Evidence of ripple marks in <20 m, no active sand waves

West Florida Shelf

Predominantly diurnal, but mixed and semidiurnal, low magnitude 0.3-1.2 m; tidal currents generally <8 cm/s

Generally low, most 0.3-1.3 m (summer-winter)

Seasonal wind-generated currents and waves, hurricanes, winter frontal passages

Localized turbidity fronts, seasonal sand ripples, near-bottom nepheloid layers influenced by storms, frontal passages, bottom currents; strong nepheloid layer at mid shelf

North Central Gulf of Mexico

Predominantly diurnal, but mixed and semidiurnal low magnitude 0.3-1.2 m; tidal currents generally <8 cm/s

Generally low wave regime, most 0.5-1.0 m (summer-winter)

Seasonal wind-generated currents and waves, particularly in winter, high frequency of hurricanes, winter frontal passages

Spring turbid bottom waters (surface also) near Mississippi River, water column turbid whole depth in winter

Northwestern Gulf of Mexico

Diurnal and mixed, low magnitude 0.5-1.5 m; tidal currents low, ≤14 cm/s

Low wave regime 0.5 m in summer to 1.0 m in winter, historical maximum of 7.3 m in summer

River discharge, inshore efects as far west as Galveston, wind-generated currents and waves, high frequency of hurricanes, winter frontal passages, widespread seasonal hypoxia

Nepheloid layers and turbidity currents, near-bottom nepheloid layer present all seasons except winter, in <20 m associated with wind-generated currents

South Texas

Mixed diurnal and semidiurnal, low magnitude 0.4-0.5 m; tidal current velocity ≤14 cm/s

Low wave regime, most 0.9-1.8 m; summer, most 0-0.6 m; winter, most 1.2-1.8 m; waves up to 2-3 m in hurricanes

Persistent SE winds predominate, along with winter northerly winds cause wind-generated currents and waves, high frequency of hurricanes, winter frontal passages

Near-bottom turbidity all seasons, variable in thickness and distribution, related to thermal mixing, internal waves, nearshore suspension by waves and tidal mixing

Southern California

Mixed semidiurnal, of moderate magnitude, 0.3-2.5 m

Average significant wave heights 1-2 m, tsunamis with waves of 6.3 m

Wind-generated nearshore water movements, prevailing winds from NW (16-32 km/hr), more onshore in summer, spring, and summer upwelling, occasional small tsunamis, periodic El Niño events, seismicity

Sediment erosion from exposed shallow shelf with deposition in basins of southern California borderland

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

Central and Northern California

Mixed semidiurnal of moderate magnitude, 0.3-2.3 m

Average significant wave heights of 1-3 m, storm waves of 5-11 m, tsunamis with waves of 6.3 m

Severe extratropical winter storms, moderate storm surges of 0.5-1 m more common, spring and summer upwelling, occasional tsunamis, seismicity

Winter storm dominated sedimentary regime with sediment deposition off major northern California rivers

Washington-Oregon

Mixed semidiurnal of moderate magnitude, up to 3 m in spring off Oregon

Average wave heights greater than to south, tsunamis with waves of 6.3 m

Severe extratropical winter storms, spring and summer upwelling, occasional tsunamis

Mid-shelf silt deposits transient and undergo repeated resuspension and redeposition by storm-induced bottom currents

Gulf of Alaska

Mixed semidiurnal, mean range at Kodiak 0.9-3-.3 m, in NE 2-4 m; swift tidal current in Cook Inlet averages 300 cm/s

High waves in storms (9 m and higher), 3 m waves prevalent in winter, maximal tsunami waves up to 33 m

Extreme storm conditions with winds up to 160 km/hr, floe ice and pack ice in Cook Inlet in winter, tsunamis, seismicity and volcanism

In general, little suspended matter due to strong currents and winter storm waves which prevent sediment accumulation, water exiting Cook Inlet with high suspended sediments (5-200 mg/l) which flows into Shelikof Strait

Bering Sea

Mixed semidiurnal tides with marked diurnal inequalities; in southern area near peninsula and land restrictions up to 5 m, in NE tides <0.5 m

Larger waves in SE up to 10-20 m, lower in NE up to 7 m, maximum wave heights 32 m, waves most influential in shallow Norton Sound and Bristol Bay

Severe storms may double strength of wind-generated currents and waves, N-S differences in storms; ice movements, dense coverage, ice presence, N-S differences; tsunamis in North Aleutian shelf; potential seismicity and volcanism

In NE, major storm surges every several years resuspend and transport sediments; dynamic sediment transport by ice gouging, storm waves, and ice loading

Alaskan Arctic

Mixed semidiurnal tides with mean range of 10 to 30 cm, small tidal currents of 0.3-0.5 cm/s

Extreme storm waves not as likely as in Bering Sea or Gulf of Alaska because generation hampered by pack ice, 2.5 m waves during storms, only 22% >0.5 m

Severe storms with high winds but waves tempered by sea ice, gouging by offshore pack ice, offshore subsea permafrost, active ice flow lead along Chukchi Sea coast, coastal erosion on Beaufort Sea coast

Storm-affected sediments in Chukchi Sea, ice gouging on seabed out to 60 m in whole area; low coastal sediment transport inshore on Beaufort Shelf, some reworking of coarse sediments by hydrodynamic forces on inner and central shelf

Source: Adapted from Rabalais and Boesch, 1987.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

TABLE 3-3 Temperature Regimes, Biogeographic Affinities, and Literature References to Benthic Studies

 

Bottom temperature regime (winter °C to summer °C)

   

Region

Inner shelf

Outer shelf

Shelfbreak

Benthic studies

Biogeographic

affinities

New England

0.5-4° to 10-12°

4-5°-~8°

10°

Wigley, 1965; Wigley & McIntyre, 1964; Wigley & Theroux, 1976, 1981; Maurer & Lethem, 1981a,b; Michael, 1977; Michael et al., 1983; Battelle/WHOI, 1983, 1984

Boreal or cold water assemblage

Middle Atlantic Bight

1-4° to 14-17° with latitudinal differences

5-8° to 13-14°

10-12°

Gross, 1976; Wenner & Boesch, 1979, Schaffner & Boesch, 1982; Boesch & Bowen, in press

Transitional between cold water assemblage to north and warm, temperate south of Cape Hatteras, shallow water Carolinian affinities, offshore boreal affinities

South Atlantic Bight

6-10° to 28° with latitudinal differences

12-17° to 26-27° with latitudinal differences

15-17° [14-21°]

Williams et al., 1968; Day et al., 1971; Tenore, 1979; Herbst et al., 1979

Warm, temperate Carolinian affinities inshore with subtropical and tropical affinities offshore

West Florida Shelf

20 to 26° with latitudinal differences

20° to 24° with latitudinal differences

16° to 22° with latitudinal differences

State Univ. Syst. Flor., 1977; Dames & Moore, 1979; Woodward-Clyde & Cont. Shelf Assoc., 1983; Lyons, 1980; Collard & D'Asaro, 1973; Lyons & Collard, 1974

Shallow shelf with Carolinian affinities, deep shelf with West Indian/tropical affinities

North Central Gulf of Mexico

~12-15° to 29°

~18-19° to 21-25°

~19° to 22°

State Univ. Syst. Flor., 1977; Dames & Moore, 1979; Lyons & Collard, 1974

Warm, temperate Carolinian affinities, separated by some from northern Gulf W of Mississippi River, outer shelf tropical affinities

North-western Gulf of Mexico

15-16° to 27-28°

18-19° to 21-25°

19-20° to 22°

Ward et al., 1979; Bedinger, 1981; Middleditch, 1981; Jackson, 1977; Hann & Randall, 1980; DeRouen et al., 1982

Warm, temperate Carolinian affinities, separated by some from northern Gulf E of Mississippi River, outer shelf tropical affinities

South Texas

14-15° to 28° with latitudinal differences

15-17° to 25° with latitudinal differences

19-22° with latitudinal differences

Holland 1977, 1979; Flint, 1981; Flint & Holland, 1980; Flint & Rabalais, 1980a,b, 1981

Mostly warm, temperate Carolinian affinities with more subtropical influence, considered by some as Texas transitional between temperate and tropical outer shelf tropical affinities

Southern California

12-14° to 17-19.5° with latitudinal differences

10-13° to 15-17°

10-13° to 15-17° @ 200m 8-9° throughout year

Jones, 1969; Barnard & Hartman, 1959; Barnard, 1963; Fauchald & Jones, 1977, 1978; Balcom, 1981

Transitional between southern subtropical Panamanian province and northern temperate Oregonian province

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

Central and Northern California

10° to 14° with latitudinal differences

9-10° to 12-13°

9-10° to 12-13°

Jones & Stokes Assoc., Inc., 1981

Temperate, Oregonian province

Washington-Oregon

9-10° to 12-13°

9-10° to 12-13°

9-10° to 12-13°

Carey, 1972; Lie & Kelley, 1970; Lie & Kisker, 1970; Richardson et al., 1977

Temperate, Oregonian province

Gulf of Alaska

<2° in May, 1-2° to 6-9° in <100 m over shoals on Kodiak where water nearly isothermal

2-3° in May

4-5° throughout year at Kodiak shelf break

Feder and Matheke, 1979; Feder & Jewett, 1980

 

Bering Sea

<−1.5 to 8-10° with latitudinal and depth differences

−1-0° to −1-2° with latitudinal differences

1-3° to 2-4° with latitudinal differences

Hood & Calder, 1981; Stoker, 1981; Haflinger, 1981; Feder & Jewett, 1981; Nelson et al., 1981

Primarily boreal Pacific

Alaskan Arctic

−1-4° in summer to −1° in fall with most values at −1-10°

2° in summer to −1.5° in fall

0° in summer to −1° in fall

Carey et al., 1974, 1984; Carey & Ruff, 1977; Bilyard & Carey, 1979, 1980, Broad et al., 1981; Stoker, 1981

Primarily boreal Pacific in Chukchi with more Arctic species than Bering Sea; dominance of amphiboreal species in Beaufort, many also occur in temperate or tropical latitudes, or both

Source: Adapted from Rabalais and Boesch, 1987.

In addition to providing valuable support for descriptive studies of U.S. continental shelf habitats, the ESP has contributed to our understanding of marine biogeography, animal-sediment relationships, and the importance of shelf ecosystems in food-chain dynamics. In recent programs, the fate of chemicals in continental shelf habitats (Bothner et al., 1983; Boehm and Farrington, 1984; Boehm, 1987; Boehm et al., 1987; Boehm et al., 1990), the interaction of biological and physical processes in benthic environments and bottom boundary layer processes (Battelle/WHOI, 1983; Butman and Moody, 1983), and the effects of exploratory drilling (Neff et al., 1989) have been examined. Through both ESP and the National Oceanic and Atmospheric Administration's Outer Continental Shelf Environmental Assessment Program (NOAA/OCSEAP) efforts, advances in analytical chemistry have been achieved for assessing low-level contamination associated with discharges of oil and gas exploration and production (MacLeod et al., 1979, 1980, 1982, 1984, 1985, 1988; Krahn and MacLeod, 1982; Malins et al., 1984).

In summary, the ESP has succeeded in characterizing OCS frontier areas of interest for oil and gas development, although not to the point where temporal and spatial variability could be discerned; demonstrating that these areas are relatively uncontaminated with trace metals and petroleum hydrocarbons, but in some instances slightly contaminated by other

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

TABLE 3-4 Dominant Benthic Assemblages

 

Dominant macrofauna

Region

Inner shelf

Outer shelf

Shelf break

New England

60 m—top of bank: Tellina agilis (b), Pseudunciola, Protohaustorius (a), Polygordius, Exogene, Hebes, Spiophanes (p), Echinarachnius (ecd)

80 m: syllid polychaetes, Phallodrilus (o), Unciola, Erichthonius, Byblis (a)

Paraonid, capitellid, cirratulid polychaetes, Ampelsica (a); in another study: Pseudohaustorius, Protohaustorius, Trichophoxus (a)

Middle Atlantic Bight

~20-30 m, dynamic sands: interstitial feeders, Tanaissus (t), Polygordius, Goniadella, Lumbrinerides (p)

~40-100 m: fewer interstitial feeders and more amphipods, Unciola, Ampelisca, Erichthonius, Photis, Rhepoxinius (a), Spiophanes, Goniadella, Lumbrinerides, Euchone, Lumbrineris (p)

~110-200 m: increase in burrowers and subsurface deposit feeders, Onuphis, Lumbrineris, spiophanes, Aricidea (p), Harbansus (os), Amphioplus (op), Ampelisca, Unciola (a)

South Atlantic Bight

<40 m “turbulent zone”: Paleanotus, Polygordius, Lumbrineris (p), Protohaustorius, Maera (a)

40-124 m, more quiescent zone: Onuphis, Spiofillicornis, Chaetozone, Pomatoceros (p), Siphonocoetes (a)

160-205 m: Odontosyllis, Onuphis, Lumbrineris, Prionospio, Chaetozone (p), Paraphoxus, Unciola (a), Nucula (b)

West Florida Shelf

>40 m: Fabricia, Vermiliopsis, Prionospio, Hydorides, Lumbrineris, Goniadides, Ehlersia (p), Photis, Maera (ga), Cyclaspis (cu), Phtisica (cp), Lucina (b)

40-100 m: Magelona, Ceratocephale, synelmis, Schistomeringo, Tharyx, Prionospio, Ampharete (p), Lucina (b), Selenaria (br)

100 m: Glycera, Prionospio, Synelmis, Terebellides (p)

North Central Gulf of Mexico

Not delineated

Dominants for entire shelf: Syllis, Sphaerosyllis, Websterinereis, Glycera, Lumbrineris, Prionospio, Paraprionospio, Mediomastus (p)

Not delineated

Northwestern Gulf of Mexico

Lumbrineris, Paraprionospio, Magelona, Sigambra, Diopatra (p), Golfingia (s), Ampelisca (a)

Cossura, Ninoe, Nephtys, Notomastus, Lumbrineris, Paraprionospio (p), Corbula, Nuculana (b), Volvulella (g)

No shelf break stations

South Texas

~15-30 m: Magelona, Nereis, Mediomastus, Aricidea, Prionospio, Paraprionospio (p), Tellina (b), Ampelisca (a)

~40-90 m: Paraprionospio, Cossura, Nephtys, Paraonis, Magelona, Asychis, Notomastus, Mediomastus (p), Ampelisca (a), Apseudes (t), Eudorella (cu)

~100-135 m: Paralacydonia, Tharyx, Sternaspis, Paraonis, Sigambra (p), Xenanthura (i), Amygdalum, Nuculana, Pitar (b), Alternochelata (os)

Southern California

<25 m, dynamic sands: Sipunculus (s), Loimia, Ophelia, Nephtys, Nothria, Prionospio, Diopatra (p), Tellina (b), Amphipholus(op), Diastylopsis (cu), Paraphoxus (a)

28-109 m: Pectinaria (p), Heterophoxus, Paraphoxus, Westwoodilla (a), Parvilucina, Tellina (b), Euphilomedes (os), Listriolobus (ech)

161-620 m: Pectinaria, Prionospio, Maldane (p), Ampelisca (a), Limifossor (g), Allocentrotus, Brissopsis (ecd), Amphiodia (op), Cyclocardia (b)

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

Central and Northern California

Sands of shallow shelf: Diopatra, Nothria (p), Dendraster (as), amphipods

Not delineated

Not delineated

Washington-Oregon

~35 m, inner shelf sands: Diastylopsis (cu), Ampelisca, Paraphoxus (a), Tellina, Macoma (b), Owenia, Nephtys, Chaetozone (p)

~95 m, intermediate shelf sands: Magelona, Sternaspis, Nephtys, Haploscoloplos (p), Yoldia, Macoma, Axinopsida (b), Paraphoxus (a)

~150 m deep-water muds: Prionospio, Sternaspis, Ninoe (p), Axinopsida, Adontorhina, Macoma (b), Heterophoxus (a), Brisaster (ecd), Ophiura, Amphioplus (op)

Gulf of Alaska

NE: inshore, deposit feeders (worms) predominate (61-65% of sample), Nucula, Nuculana, Yoldia, Thyasira, Axinopsida (b), Terebellides, Nereis, Lumbrineris, Sternaspis (p), Heterophoxus (a), Chaetoderma (ap), Diamphiodia (op)

Same as inner and mid shelf

NE: shelf break and slope, more suspension feeders (clams), comprise 32% of sample, deposit feeders 26%, Notoproctus, Glycera, Sabellids, syllids (p), sipunculids, brachiopods, Astarte (b), Anonyx (a)

Bering Sea

Byblis, Ampelisca (a), Capitella, Ampharete, Haploscoloplos, Myriochele, Sternapsis (p), Cylinchna (g), Serripes (b), Diamphiodia, Gorgonocephalus (op)

Axinopsida, Tellina, Yoldia, Clinocardium (b), Byblis, Bathymedon, Protomedeia (a), Capitella, Haploscoloplos, Brada, Artacama (p), Echinarachnius (ecd), Chaetoderma (ap)

Aricidea, Glycera, Asabellides, Harmothoe, Maldane (p), Ampelisca (a), Ophiura (op), Golfingia (s), Astarte, Hiatella (b)

Alaskan Arctic

In Chukchi similar to Chukchi outer shelf; in Beaufort, inshore zone <20 m, polychaetes, gammarid amphipods, isopod, bivalves, priapulid

Chukchi: Maldane (p), Astarte, Macoma, Nucula, Yoldia (b), Ophiura (op), Golfingia (s), Pontoporeia (a); Beaufort: offshore zone (20-200 m), fauna not delineated

In Chukchi, similar to outer shelf, in Beaufort, not studied

NOTE: Abbreviations for taxa are: a—amphipod, ap—aplocophoran, as—asteroid, b—bivalve, br—bryozoan, cu—cumacean, ca—caprellid, ecb—echiuran, ecd—echinoid, g—gastropod, ga—gammarid amphipod, i—isopod, o—oligochaete, op—ophiuroid, os—ostracod, p—polychaete.

Source: Adapted from Rabalais and Boesch, 1987

anthropogenic activities; and improving our understanding of the minimal effects of exploratory drilling on shelf habitats (although to a large extent studies of the toxicity and sublethal effects of exploratory drilling were supported by industry and other federal agencies).

Shortcomings of the Environmental Studies Program

In spite of detailed characterizations, it is difficult to determine the vulnerability of shelf ecosystems to OCS activities and the recovery of the ecosystems (Rabalais and Boesch, 1987). Although the relative sensitivities of coastal habitats to oil spills have been evaluated (Gundlach and Hayes, 1978; Owens and Robilliard, 1981), little effort has been spent on comparing the sensitivities of shelf habitats or assessing OCS impacts other than oil spills.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

TABLE 3-5 Other Benthic Assemblages

Region

Macrofaunal variability

Epifaunal predators

Hard substrates and rare habitats

New England

Regional stations distinct by depth and sediment type across seasons during two years, little seasonal variability with differences not reputable over two years

Gadid fishes, flatfishes, cancroid crabs, starfish

Epibenthic and soft coral communities at heads of submarine canyons

Middle Atlantic Bight

Variability related to mesoscale topography, bathymetric gradients related to temperature, temp. variability, frequency and magnitude of sediment disturbance, variability of population and community structure decreases with depth

Gadid fishes, flatfishes, cancroid crabs, starfish

Epibenthic and soft coral communities at heads of submarine canyons

South Atlantic Bight

High seasonal variability and year-to-year differences nearshore, variability with depth related to frequency and magnitude of sediment disturbance as well as sediment distribution

 

Shallow coral patches near shore, calcareous reefs at shelf break, scleratinian coral reefs at shelf break off Florida

West Florida Shelf

Seasonal differences in community structure, particularly nearshore, faunal differences related to bathymetry and sediment distributions

Penaeid and sicyonid shrimp, portunid crabs, sea basses, flatfishes, holothurians (bioturbation)

Numerous hard substrates with epibenthic fauna and hermatypic corals, algal nodule substrates, nearshore seagrass beds, Florida Middle Grounds

North Central Gulf of Mexico

Seasonal differences with decreases in polychaete taxa and density and crustacean density in winter, variability in polychaete density with depth related to sediment differences

Penaeid and sicyonid shrimp, portunid crabs, sciaenid fishes, flatfishes

Exposed hard substrate areas on outer shelf and at shelf break

Northwestern Gulf of Mexico

Seasonal changes in abundance and dominance, variability in community structure related to sediment differences both with depth and physiography and to seasonal hypoxia on inner shelf

Penaeid shrimp, portunid crabs, sciaenid fishes, flatfishes

Exposed salt dome banks of carbonate sediments on outer shelf and shelf break, many with hermatypic corals, most with top environmental priority ranking, East and West Flower Gardens

South Texas

Some seasonal differences but not consistent over depth or latitude gradients, large-scale community differences related more to sediment distributions and hydrographic variability

Penaeid shrimp, portunid crabs, sciaenid fishes, flatfishes

Exposed salt dome banks of carbonate sediments on outer shelf, most with low diversity epibenthic communities, most with low environmental priority ranking

Southern California

Seasonal recruitment shown by aggregations of Amphiodia in summer on mainland shelf, no apparent seasonality in basins; large-scale differences related to complex topography

Sea basses, sciaenid fishes, sea urchins and starfish, cancroid crabs, pandalid shrimp

Scattered submerged ridges and topographic highs in complex borderland, rocky banks at shelf edges, some in shallower water with purple coral (Allopora), others with rich epibiota; kelp forests, Tanner and Cortez Banks

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

Washington-Oregon

Increases in density, diversity and standing stock with depth

Cancroid crabs, flatfishes, rock fish

 

Gulf of Alaska

In NE, east/west differences, increase in diversity at shelf break, differences in community structure related to sediment differences and sedimentation rate

Lithodid and cancroid crabs, pandalid shrimp, flatfishes, sea urchins and starfish

Area of bedrock extending from Kayak Island to 200 m, gravel areas at shelf break with communities similar to those of hard substrate areas

Bering Sea

No seasonal or annual standing stock differences over 5 years, “relatively stable”; most nearshore/offshore differences or large-scale differences related to sediment distributions, latitudinal differences related to sea ice dynamics

Lithodid crabs, pandalid shrimp, flatfishes, codfish, starfish, marine mammals

Yukon River delta area

Alaskan Arctic

In Chukchi, no seasonal or annual standing stock differences over 5 years, “relatively stable”; in Beaufort, longitudinal variability related to warmer Bering-Chukchi water in W and E-W sediment differences, seaward differences related to sea ice dynamics

Whitefish, cisco, grayling, arctic char, arctic cod, flatfishes, sculpin, marine mammals

Boulder areas on inner shelf with epibiotic communities, Boulder Patch in Stefansson Sound, kelp forests, Colville River delta area

Source: Boesch and Rabalais, 1987.

Rabalais and Boesch (1987) concluded that four features of continental shelf habitats could be used for a comparative evaluation of habitat sensitivities:

  • Sedimentary regime, with depositional areas being the ultimate repository of particle-bound contaminants.

  • Temperature, which controls rates of both biodegradation and recolonization by benthic organisms.

  • Depth, which influences rates of recolonization and recovery after disturbance.

  • Biogenically structured communities, where species interactions control the recovery, e.g., coral reefs, mangroves.

To a large extent, benthic studies have been largely descriptive, or observational, and, because of design inadequacies, have failed to increase our ability to predict impacts on the OCS. Carney (1987) concluded that the inadequacies of many benthic surveys resulted from the lack of an operational definition and understanding of potential impacts, the lack of a stated hypothesis for delineating impacts and distinguishing impacts from natural variation, and a failure to use appropriate statistical techniques for population surveys.

Too little emphasis has been placed on process-oriented studies, including studies of sediment dynamics, trophic interactions, recruitment mechanisms, and biogeochemical cycling. With the exception of data from recent studies in the north Atlantic, California, and the Beaufort Sea, OCS frontier areas lack sufficient data to support predictions of the long-term fate and effects of operational discharges or an understanding of large-scale consequences of changes in benthic populations.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

TABLE 3-6 Continental Shelf Regions of the United States Compared with Planning Areas of MMS.

Region

Coastal boundary

MMS offshore planning areas

ATLANTIC COAST

 

New England

 

North Atlantic

 

Montauk Point

 

Middle Atlantic Bight

 

Middle Atlantic

 

Cape Hatteras

 

South Atlantic Bight

 

South Atlantic

GULF OF MEXICO

 

West Florida Shelf

 

Eastern Gulf

 

Cape San Blas

 

North Central Gulf of Mexico

 

Eastern Gulf (in part)

 

Louisiana-Mississippi border

 

Northwestern Gulf of Mexico

 

Central Gulf

Western Gulf (in part)

 

Matagorda Bay

 

South Texas

 

Western Gulf

PACIFIC COAST

 

Southern California

 

Southern California

 

Point Conception

 

Central and Northern California

 

Southern California (in part)

Central-Northern California

 

California-Oregon border

 

Washington-Oregon

 

Washington-Oregon

ALASKA

 

Gulf of Alaska

 

Gulf of Alaska

Kodiak

Cook Inlet

Shumagin

 

Aleutian Islands

 

Bering Sea

 

North Aleutian Basin

St. George Basin

St. Matthew Hall

Navarin Basin

Norton Basin

 

Bering Strait

 

Alaskan Arctic

 

Hope Basin

Chukchi Sea

Beaufort Sea

Source: Adapted from Rabalais and Boesch, 1987.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

The ESP has focused mostly on frontier areas of the OCS to provide baseline information for lease sales. But analyses of potential long-term effects of OCS activities have concluded that the most important impacts are expected to occur during development and production, and not during exploration (Boesch et al., 1987). A greater balance should be achieved between studies conducted in frontier areas and studies conducted in areas where development and production are occurring (e.g., northwestern Gulf of Mexico) or are likely to occur. MMS should expend more resources on examining benthic communities on the shelf slope and rise (i.e., within the 200-mile EEZ). The panel notes that a preliminary survey has been done on the slope of the Gulf of Mexico (Gallaway, 1988). Greater attention should also be placed on characterizing the impacts of all operational discharges from OCS activities. The effects of drilling-fluid discharges have been reviewed extensively (NRC, 1983); water-based drilling fluids used in U.S. OCS areas are relatively nontoxic and pose little long-term or large-scale risks to benthic systems. Little attention has been focused on the fate and effects of produced waters, a potentially more important source of toxic contaminants.

A final shortcoming of the ESP is a lack of continuity in technical expertise from one study to the next. That seems to be a result of the infrastructure of MMS's “procurement” approach, rather than a research-and-development approach, to program administration.

Design of Benthic Monitoring Programs

Ecologists in all disciplines have long recognized the importance of good time-series data. They have produced powerful and unexpected insights into oceanic systems. In each case, a particular goal was initially instrumental in setting up long-term sampling programs, but each program yielded convincing and important results that illustrate the power of even crude time-series data in testing hypotheses and predictions. Furthermore, the data base for each has provided new and nonintuitive insights into the functioning of ocean systems; they are particularly useful in establishing the importance of physical forcing of biological events. Although such studies have usually been harmed by struggles over financing, the power of time-series data is so great that even studies flawed by budget cuts have contributed to our understanding.

A major problem in benthic ecology is understanding the factors that influence the dispersal and local abundance of the long-lived pelagic larvae typical of most benthic invertebrates. Many instances of strong, episodic benthic recruitment almost certainly result from large-scale variation in larval abundance or dispersal processes. Those episodes represent the normal state of affairs for large, long-lived benthic species, such as flatfishes, crabs, lobsters, abalones, and most echinoderms. The patterns of distribution revealed by large-scale benthic studies result from episodic recruitment; it is important to recognize that episodic recruitment must be evaluated in decades, rather than years. Thus, long-term programs like the California Cooperative Fisheries Investigations (CalCOFI) program, but with appropriate spatial and temporal resolution for benthic studies, would be useful in areas with active development and production, i.e., in the Gulf of Mexico and southern California (where the existing CalCOFI program should be strengthened).

Understanding Benthic Processes

It is insufficient for a monitoring program to document an effect without also providing

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

an understanding of the mechanistic processes that produced the effect (Carney, 1987). Establishing mechanisms often requires some well-designed field or laboratory experiments to complement the monitoring process. Many variables are inextricably confounded in nature in such a way that their effects can be separated only through experimentation (Carney, 1987). Mesocosms (experimental setups larger than those typically found in indoor laboratories), flumes, or small experimental setups are potentially important in permitting observations of organism behavior and various biological interactions that are necessary to form a complete understanding of benthic processes. Mesocosms and other laboratory systems must be used appropriately, lest laboratory artifacts confound the results (Capuzzo, 1987; Underwood and Peterson, 1988). Although laboratory and mesocosm studies are restricted to studies of processes on smaller spatial scales, they provide a valuable link between field investigations by defining the biological and geochemical characteristics responsible for contaminant transport and effects. Furthermore, only through careful experimentation can complex interactions, such as nonadditive effects and higher-order interactions among variables, be detected and understood.

To measure the important variables on appropriate spatial and temporal scales, a conceptual model is needed of the hypothesized processes by which anthropogenic activities could be influencing the benthic biota. That might be self-evident, but such models are almost never used—an appalling omission. A monitoring program that is not linked to an assessment of various reasonable models of processes will gather data of very limited usefulness. For fuller evaluation of the processes by which anthropogenic activities influence the benthos of the continental shelf, modeling efforts should ultimately become numerical or analytical, at least for the physical processes of importance.

Biogeochemical Concerns

The transfer of contaminants derived from oil and gas activities on the continental shelf to marine biota depends on several factors that govern the fate of specific contaminant classes. Contaminants can accumulate in biological resources through aqueous, dietary, or sedimentary pathways, and the relative importance of each pathway depends on both chemical factors, such as compound solubility and adsorption-desorption kinetics, and biological factors, such as feeding habits and metabolism. For both trace metals and organic contaminants, factors that influence bioavailability must be resolved before uptake and potential damage to biota can be estimated (Boehm, 1987). Low-molecular-weight hydrocarbons and other partially oxidized organics found in produced waters are highly water-soluble and would be diluted rapidly on discharge. Uptake of those hydrocarbons by marine biota has been demonstrated (Armstrong et al., 1979), and the residence time of accumulated hydrocarbons can be much longer in marine biota than in the water column. Neff (1987) recently reviewed studies of the fate and effects of discharged drilling fluids and produced waters. He concluded that assessment of the importance of long-term exposure required more detailed characterization of the hydrocarbon and tracemetal composition of produced waters from different coastal and continental shelf sources. Accumulation of chemical components in the surface microlayer might result in the exposure of surface-dwelling eggs and larvae to high concentrations of toxicants (Hardy et al., 1987a,b).

The effect of oil spills on marine biota has been the subject of several recent reviews (NRC, 1985; Capuzzo, 1987; Spies, 1987). Data on several recent oil spills suggest that the medium- and higher-molecular-weight aromatic hydrocarbons, such as alkylated phenanthrenes and alkylated dibenzothiophenes, are among the most persistent petroleum hydrocarbons in both animal tissues and sediments (Grahl-Nielsen et al., 1978; Roesijadi et al., 1978; Teal et al., 1978;

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

Boehm et al., 1981, 1982; Farrington et al., 1982; Boehm, 1983). Thus, although short-term effects can result from acute exposure to a wide range of hydrocarbons, long-term chronic effects probably result from exposure to medium- and higher-molecular-weight aromatic hydrocarbons (Boehm, 1987), and the response of marine ecosystems to off exposure has been linked to the persistence and degradation of these hydrocarbons. Data from off spills—such as the West Falmouth off spill (Sanders et al., 1980), the Tsesis off spill (Elmgren et al., 1983), the Amoco Cadiz spill (Berthou et al., 1987), and the Galeta spill (Jackson et al., 1989)—confirm the relationship between the persistence of petroleum hydrocarbons and long-term recovery of benthic biota. Biological effects of oil spills and chronic petroleum discharges are greatest in low-energy environments from which physical removal of hydrocarbons is slow.

The ultimate fates of spilled petroleum or operational discharges depend primarily on the ability of microorganisms to use hydrocarbons as sources of carbon and energy (NRC, 1985). However, no crude off is completely biodegradable. The polar fractions of petroleum and most molecular fractions that contain nitrogen, sulfur, and oxygen are essentially nonbiodegradable (NRC, 1989b). The paraffinic fractions are readily degradable under ideal conditions (Payne et al., 1987). The absolute amount and rate of biodegradation of any petroleum depend on its composition and the specific abiotic environmental conditions.

Microorganisms capable of degrading a variety of petroleum hydrocarbons are widespread in aquatic environments (Atlas et al., 1981; Bauer and Capone, 1988). In response to the Amoco Cadiz oil spill off the coast of France, microbial populations changed in their ability to degrade hydrocarbons (Ward et al., 1980). Similarly, the numbers of hydrocarbondegrading bacteria vary by several orders of magnitude among sites sampled after the Exxon Valdez oil spill (Brown and Braddock, 1990). Several studies cited by Bartha and Atlas (1987) in their extensive review of hydrocarbon metabolism by microorganisms showed positive correlations between the numbers of hydrocarbon-degrading microorganisms and oil-pollution patterns.

In general, the rate of petroleum biodegradation in marine waters is not limited by oxygen or temperature, but rather by the availability of inorganic nutrients. The most toxic low-molecular-weight aromatic fraction of crude oil in the water does not generally persist long. However, although a “light transparent fuel oil” spilled in 1969 became invisible within days, chemical analyses could detect fractions of the oil in the water for up to 8 months (Blumer et al., 1971).

In nutrient-rich (organic) marine sediments, oxygen concentration is the primary environmental variable that controls rates of degradation, especially of the more complex aromatic fractions of petroleum. Urban estuaries, such as Boston Harbor, can contain polycyclic aromatic hydrocarbons at up to 100 mg/gram of sediment. Once confined in aquatic sediments, the more complex fractions remain for indeterminate periods. Where long-term persistence of petroleum hydrocarbons has been documented, sublethal effects have been observed. Krebs and Burns (1977) studied populations of fiddler crabs (Uca pugnax) for 7 years after the West Falmouth spill of no. 2 fuel oil and observed long-term reductions in recruitment and population density, changes in sex ratios of adult crabs, behavioral changes, and increases in overwintering mortality. After the release of 8,000,000 liters of medium-weight crude oil from a ruptured off-storage tank at the refinery on Isla Payardi in the Republic of Panama, Jackson et al. (1989) observed changes in stomatopod behavior and population structure, increased coral injury, and overgrowth by algae. Garrity and Levings (1990) observed reduced recruitment of snails at the same site for 2 years after the spill.

Salinity, temperature, mineral nutrients, oxygen availability, hydrocarbon concentration, biomass, acclimation of microbes to a particular hydrocarbon, and other factors can affect rates

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

of hydrocarbon transformation (Bauer and Capone, 1988). Acclimation implies induction and growth of microorganismic enzyme systems capable of transforming hydrocarbons. The induction and growth depend on hydrocarbon concentration and the initial biomass of microorganisms present. Because petroleum is not a single defined organic compound, monitoring its biodegradation or transformation is complex and demanding. Indirect techniques (such as CO2 evolution, O2 consumption, and enzyme assays) can be used to estimate the overall fate of petroleum in water or sediments. With such methods, in situ hydrocarbon degradation rates in water have been estimated at 0.001-60 g/l per day (Bartha and Atlas, 1987).

Statistical Analyses

Environmental monitoring suffers conspicuously from the lack of adequate statistical test designs. A complete program of environmental monitoring should include support for development of statistical procedures appropriate to the specific problems being addressed. As in any scientific investigation, samples for environmental monitoring must be carefully constructed in combination with the statistical test that is contemplated to permit appropriate and effective testing of hypotheses (Carney, 1987). Testing of environmental impacts with monitoring data, however, poses special problems. First, many variables covary in natural systems, so separation of their influences is difficult or impossible. Second, appropriate “control” (untreated) sites might not exist, especially in tests of the effects of pervasive processes that could influence the benthos on large temporal or spatial scales. Third, replication of treated sites might be impossible, if there is only a single impact locality; this does not prevent rigorous testing of a potential impact at the site, but the site-specific nature of such tests renders extrapolation and generalization of the results risky or even impossible.

An example of the successful development of a rigorous test for site-specific impacts is the “BACI” test of Stewart-Oaten et al. (1986), which uses a creative solution of the general problem of achieving replication and identifying an appropriate control site. The test uses temporal replication before application of the environmental impact and provides temporally replicated estimates of the usual (pretreatment) differences between a control and an impact site. The pretreatment differences are then compared statistically against a time-series of differences after application of the impact.

A branch of applied statistics that needs further development to enhance environmental monitoring studies is power analysis. Power analysis is so rare in ecological studies that no universal standard has been established. Furthermore, the power of a test depends entirely on the size of the difference that one would like to be able to detect. Thus, in monitoring studies, it is important to determine the magnitude of impact that is deemed serious, so that power can be calculated against the appropriate alternative hypothesis. That is rarely if ever done. There is even merit in considering increasing the probability of rejecting a true null hypothesis, to increase power in environmental monitoring studies. All these issues require further analysis and development by experts in applied statistics.

Biological Hierarchy

Anthropogenic effects on benthic organisms can potentially be detected at a wide variety of organizational levels, ranging from molecular or cellular responses to ecosystem responses. It is prudent to conduct simultaneous tests for the influence of anthropogenic activities on the

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

benthos at several levels of biological organization. Some tests at the cellular or physiological levels could prove to be more sensitive and better able to detect effects of anthropogenic influences, whereas changes at the population and community levels might more commonly reflect important consequences of those influences.

Most studies of marine benthic impacts have focused almost exclusively on detection of impacts without addressing their consequences. But the issue of consequences should be an important element of any program to study anthropogenic impacts on benthic populations of the continental shelf. Anthropogenic impacts can be measurable but of only trivial importance and of no consequence to maintenance of biological diversity, productivity of fish and shellfish stocks, remineralization of organic matter, or even population sizes and community structure of benthic communities. Presumably, such effects would be irrelevant to protection and preservation of benthic systems of the shelf.

Many indexes of sublethal stress have been proposed for monitoring the responses of organisms to anthropogenic impacts (McIntyre and Pearce, 1980), but few have been linked to the survival potential of individuals or the reproductive potential of a population. Particularly sensitive responses that might be related to population effects include biochemical and cellular responses that are associated with energy metabolism, membrane function, or detoxification and physiological responses that influence the energy available for growth and reproduction or for other aspects of reproductive and developmental processes (Capuzzo, 1987). Although sublethal responses have been demonstrated to be sensitive to anthropogenic influences (such as chronic petroleum discharges), it is difficult to ascertain the relationship between these responses and large-scale alterations in the functioning of marine ecosystems and the harvesting of fishery resources.

Because the spatial scales of larval dispersal of continental shelf benthos are so large and the natural mortality of larval marine benthic invertebrates is extremely high, population sizes might be largely decoupled from the reproductive output of spawning adults. The decoupling of population structure from the physiological condition of individual organisms makes it important to study local effects at both levels of biological organization. The best approach to assessing the effects of anthropogenic inpacts on the marine benthos might involve an array of tests that include both studies of sublethal effects on individual organisms and measurement of changes at the population or community level.

Impairment of behavioral, developmental, and physiological processes could occur at concentrations much lower than acutely toxic concentrations and lead to alterations in the long-term survival of affected populations. Observed discrepancies between laboratory studies of acute toxicity and field assessments of the aftermath of major oil spills (Jackson et al., 1989) might be due at least in part to sublethal responses that alter the growth and reproductive potential of individuals in exposed populations.

Other Impacts

Overfishing of exploited finfish and shellfish stocks poses a qualitatively different anthropogenic impact on the benthic systems of the continental shelf. It is well established that the removal of top carnivores can have ramifications on biological interactions throughout an entire community. Bottom disturbance during trawling or dredging operations may have substantial effects on the benthic fauna, because such activities destroy the small-scale structure important for most infaunal species. It is important to note that collapse of populations due to overfishing and natural causes can be severe and sudden and can be independent of offshore

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

hydrocarbon development. Given our current understanding of processes that control benthic community structure, separation of these impacts is difficult, if not impossible.

Summary of Monitoring Design Requirements

The need for broad-scale survey work has passed, and adequate general descriptions of the benthic environments of the U.S. continental shelf are in hand (Rabalais and Boesch, 1987). Future efforts must be directed toward designing sampling programs that define the magnitude of a perturbation that will have no detectable biological effect. The ESP has the ultimate responsibility to design monitoring approaches that incorporate statistical analyses of monitoring data, interpretation of results, coordination of ancillary monitoring and research efforts, and the publication of conclusions that have been subjected to appropriate and independent peer review. The ESP has the responsibility to assess not only the impacts of offshore exploration and development, but also the effects of transportation or other support activities on shoreline habitats.

An environmental monitoring program that will improve understanding of the impacts on benthic processes of OCS activities on the U.S. continental shelf must consider:

  • Characterizing the spatial and temporal extent of impacts of discharges and disturbance, including the physical and chemical processes that regulate the fate and transport of contaminants from OCS activities.

  • Measuring direct and indirect biological effects and distinguishing them from natural variation in ecosystem structure and function.

  • Assessing the vulnerability of different shelf habitats and predicting recovery rates.

  • Developing predictive models to assess the long-term effects of OCS activities.

As our knowledge of benthic systems increases, our ability to differentiate between anthropogenic impacts and natural variation should also increase. Given the present state of knowledge, however, our ability to predict impacts is minimal. Carney (1987) recommended that future studies focus on four major questions to resolve the differences between anthropogenic impacts and natural variation in benthic systems:

  • Can impacts be related to processes that can be studied effectively in the field?

  • If a faunal census approach is used, is something other than a species-by-species approach more informative and cost-effective?

  • Can we substantially increase our understanding of the relationship between faunal and environmental spatial and temporal variation?

  • What types of powerful and robust statistical models might be most applicable to long-term effects studies?

Until those questions are answered, studies might be limited to a faunal census approach, but at the very least such studies should follow good statistical design, should be aimed at hypothesis-testing, and should use both multivariate and univariate techniques. Recent efforts of the Intergovernmental Oceanographic Commission (IOC)/Group of Experts on the Effects of Pollutants (GEEP) Workshop on Biological Effects of Pollutants held in Oslo in 1986 demonstrated the robustness of multivariate and univariate techniques as applied to higher

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

taxonomic units (i.e., family and higher) in resolving site-specific differences. The results suggest that more cost-effective approaches might be feasible in the analysis of anthropogenic impacts on macrofaunal communities and perhaps also on meiofaunal and microbial components (Bayne et al., 1988).

Preliminary surveys or reconnaissance can provide substantial information on a specific study site and provide the basis for the design of further long-term studies. Such a survey should include an analysis of the temporal and spatial patterns of faunal and environmental variables, including broad-scale characterizations of the biological, chemical, physical, and geological features of the region. Later studies should focus on defining the spatial and temporal distributions of impacts by time-series analysis of biological and other environmental features. That approach is now used in the assessment of the Santa Maria Basin and should serve as the model for future ESP benthic studies.

In the design of a sampling program for assessing the effects of offshore oil and gas operational discharges on benthic ecosystems, some effort should be used to determine the persistence and degradation rates of contaminants in sediments and the flux of these contaminants between sediments, interstitial waters, and biota. If the flux is substantial, it is important to relate contaminant content in sediments, interstitial waters, and biota to changes in benthic biomass, the structure of benthic communities, recruitment success of benthic populations, and trophic interactions. Finally, demersal fish and shellfish populations that migrate little or not at all should be used as models to relate contaminant concentrations in biota to the activity of biotransformation mechanisms, reproductive condition, and incidence of energetic abnormalities and pathology.

As a means of addressing subtle chronic impacts, such a study design must integrate an understanding of the physics of bottom boundary layers, the chemistry of bioavailability of contaminants, and the biology of population structure and function, resource use, and recovery.

FISHERIES

MMS has sponsored many studies on fishery resources and some studies on the structure and function of ecosystems. However, the studies have provided relatively few quantitative assessments of the effects of OCS oil and gas activities on fishery resources, and assessments of the effects on ecosystems are almost completely lacking. The reason is not a lack of concern, but rather the complexity of the assessment problem. As noted in Chapter 2, efforts to understand the causes of population fluctuations in fisheries have met with limited success in all programs.

Information Needed

The most basic information that is needed is the spatial and temporal distribution of fishery resources and key ecosystem components. Life-history patterns should be understood well enough to permit one to identify critical habitat whose degradation could jeopardize a population. Spawning grounds, areas of concentration of eggs and larvae, nursery grounds, and migratory routes are particularly important.

Characterizing the distribution of fishery resources and other ecosystem components is needed for assessing the relative importance of habitat. In some cases, critical habitat is remote from drilling, but can be vulnerable to onshore OCS-related activity, e.g., pipeline routings

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
×

through coastal wetlands, gravel islands and causeways in arctic regions, and channelization. One MMS study (Turner and Cahoon, 1988) examined the reasons for the loss of wetlands and the increasing rate of wetland loss in Louisiana. The study produced estimates of direct and indirect impacts on wetlands, quantified the extent of those impacts that resulted from OCS activity, and addressed some key questions regarding the mechanisms of those impacts. Critical coastal habitat can also be vulnerable to oil spills or blowouts. Quantitative assessment of the effects of OCS activity requires information on the fates of contaminant, i.e., spatial and temporal distribution of contaminants and their degradation products. Overlap in the distributions of contaminants and ecosystem components determines the magnitude of ecosystem exposure. Research on the biological effects of exposure (specified by concentration and duration) is an essential element for analysis.

Priority for studies of biological effects should be given to species that are potentially vulnerable (e.g., exposed to contaminants) and thought to be sensitive. Early life-history stages, such as eggs and larvae, are most likely to suffer lethal effects. The most important sublethal effects are the ones that can be related to demographic measures (e.g., reproductive output and growth rate) that govern the production and abundance of populations. Research might be necessary on the degree to which mobile organisms avoid and are likely to come into contact with oil and other material originating from OCS activity.

For fishery resources, traditional models of fishery population dynamics can be expanded to account for other sources of stress, such as those resulting from OCS activity (e.g., Schaaf et al., 1987). That approach takes advantage of the large literature on fish population dynamics and response to fishing.

Predicting the impacts of offshore off and gas activities requires an understanding of the responses of marine biota to both chronic small discharges of drilling fluids, formation waters, and other contaminants from platforms and accidental discharges of larger volumes from blowouts or oil spills. Biological effects of contaminant discharges on marine biota depend on:

  • Bioavailability and persistence.

  • The ability of an organism to accumulate and metabolize contaminants.

  • The interference of contaminants with normal metabolic processes so as to alter an organism's chances for survival and reproduction in the environment.

In considering the long-term effects of offshore oil and gas development activities, one should ascertain what biological effects might result in subtle ecological changes and impairment of fishery resources (Capuzzo, 1987). Rosenthal and Alderice (1976) concluded that the stages in the life cycle of marine fish (and most invertebrates) that are most sensitive to contaminant exposure are the development of gonadal tissue, early embryonic (pregastrulation) stages, the larval transition to exogenous food sources, and metamorphosis. Several investigators have shown that early embryonic and larval stages are more sensitive than later larval stages to petroleum hydrocarbons (see review in NRC, 1985; Capuzzo, 1987).

Sublethal effects of petroleum hydrocarbons on early life-history stages include a wide range of developmental and energetic abnormalities (Kuhnhold, 1974; Linden, 1976; Smith and Cameron, 1979; Linden et al., 1980; Hawkes and Stehr, 1982; Capuzzo et al., 1984). Cod and pollack eggs collected after the Argo Merchant oil spill had a high incidence of cytological deterioration and abnormal differentiation (Longwell, 1977). Effects of petroleum hydrocarbons on reproductive and developmental processes include interference with hormone synthesis (Truscott et al., 1983), impairment of gonad development (McCain et al., 1978), transfer of hydrocarbons from gonads to early developmental stages (Koster and Van den Beggelaar, 1980),

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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and reduced hatching success (Kuhnhold, 1978; Sharp et al., 1979). Sharp et al. (1979) suggested that hydrocarbon exposure of embryonic and larval stages might result in the shunting of energy reserves away from critical differentiation and morphogenic processes to metabolic maintenance.

Sublethal changes in energetics of adult organisms as a result of petroleum exposure can increase susceptibility to other environmental stresses, such as disease. Several studies have shown a direct correlation between hydrocarbon stress and increased incidence of histopathological conditions (McCain et al., 1978; Sindermann, 1982; Murchelano and Wolke, 1985). Populations of plaice (Pleuronectes platessa) collected from off-contaminated estuaries after a spill from the Amoco Cadiz had reduced growth rates and fecundity (Conan, 1982) and histopathological aberrations (Haensly et al., 1982; Stott et al., 1983). As illustrated in Figure 3-1, impairment of energetic and developmental processes occurs at much lower than acutely toxic concentrations.

Polycyclic aromatic hydrocarbons and other lipid-soluble foreign compounds are metabolized by many marine vertebrates and invertebrates (Bend and James, 1978; Stegeman, 1981). Metabolism affects the disposition or increases the removal of the compounds; it can also transform them to potentially more toxic derivatives. Malins (1982) suggested that metabolic transformation could be linked to a wide range of cytological, structural, and developmental abnormalities.

FIGURE 3-1 Comparison of lethal and sublethal effects of petroleum hydrocarbons on fish and invertebrates. Source: Vandermeullen and Capuzzo, 1983.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Long-term effects of offshore oil and gas development can be both direct (through the loss of reproductive or recruitment success) and indirect (through the disruption in food-chain dynamics). Both types of impacts are difficult to assess, because of our lack of knowledge of natural variability in reproductive effort and recruitment and of flexibility in prey selection by commercially important species of fish and shellfish. Although MMS has used oil-spill models to predict the spatial and temporal interactions of spills with eggs and larvae, little attention has been given to predicting the impact of chronic exposure on reproductive or developmental success.

MMS, through the NOAA/OCSEAP, supported numerous studies relevant to the fishery resources of the Alaska OCS, including toxicity studies related to early life-history stages of Alaska fish and invertebrate species (Rice et al, 1983); studies of sublethal effects of petroleum hydrocarbons on salmonids, king crab, and other species (Rice et al., 1983); studies of effects of hydrocarbons on cytological, cytogenetic, and histopathological disorders (e.g., McCain et al., 1978; Hawkes, 1980; Malins et al., 1982; Varanasi and Gmur, 1981); and studies of habitat and distribution of commercially important species (Rice et al., 1983). In addition, fishery models have been developed to assess the impact of OCS activities; these are discussed in the modeling section.

Those studies have provided a fundamental understanding of the broad range of responses of fishery species to petroleum hydrocarbons. Techniques developed in them are suitable for application in monitoring the effects of OCS activities, especially the short-term effects of produced waters and the long-term effects of accidental petroleum discharges. Similar studies were conducted during the evaluation of the effects of the Exxon Valdez oil spill, but the results were not available to the panel for review. A recent workshop on fisheries oceanography in the Arctic (Meyer and Johnson, 1990) identified specific research needed for assessing fishery resources at risk from oil and gas activities in the Arctic, primarily in the Beaufort and Chukchi seas. Characteristics related to the distribution, habitat requirements, and reproductive biology of important species were identified as information gaps, especially during the winter months when habitats are covered by ice.

ECOSYSTEM MODELING

Mathematical models should play an important role in assessing the effects of OCS activity, although they must be used with caution. Models of the fates of contaminants—which require focused studies of physical and geochemical processes—should be developed to assess ecosystem effects of OCS activity. Models have been used to study the fates of contaminants from acute events, such as blowouts and oil spills.

Biological Models Developed with MMS Funding
Circulation Models

Although this section is concerned primarily with fishery and ecosystem models, a brief discussion of circulation models is warranted, because the physical environment is the primary determinant of contaminant distribution. MMS has funded the development of several circulation models that range from regional-circulation models (e.g., of the West Florida Shelf) up to basin-scale models (e.g., the Gulf of Mexico). The models have been reviewed by the

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Physical Oceanography Panel, whose report (NRC, 1990a) should be consulted for details and evaluations of the models.

The current distributions obtained with the circulation models are used in two ways. First, the simulated current distributions are used in conjunction with the Oil Spill Risk Assessment model to determine statistically the direction of transport of oil discharged into the marine environment and the probability that spilled oil will reach specified “targets” (usually segments of shoreline). The trajectories produced by the model can be used to assess the risk to a particular population (e.g., sea otters or birds), if the distribution and population dynamics of the population are known. Second, the simulated current distributions can be used directly in a coupled physical-biological model as variable coefficients to provide the physical forcing that transports constituents (e.g., biological constituents or contaminants) throughout a given region. Given the importance of currents in determining the distribution of constituents in the marine environment, the assumptions and procedures used to develop the circulation model must be carefully considered before the output of one of these models is used to assess biological questions. In particular, circulation models typically are formulated to represent space and time scales that are larger than the scales that are important in biological oceanographic and fishery problems.

Population Risk Models

MMS has supported attempts to construct models to investigate the effect of oil spills on organisms, such as marine birds and mammals. Reed et al. (1986) constructed a model to consider the effects of oil spills in the Bering Sea on the population dynamics of northern fur seals in different seasons. The available data were derived from observations of fur seal migration routes and various population measures, such as reproductive and mortality rates. The primary benefit of the study was in pointing to the need for additional data, if such modeling efforts were to be predictive for natural populations.

The study of Siniff and Ralls (1988), also described earlier in this chapter, helped to predict the effects on the sea otter population of an oil spill along the California coast. Although the study was valuable in helping to predict recovery times for a population of sea otters after oil spills of different magnitudes and in different regions of the California coast, and it also demonstrated the need for additional information data on various population measures.

Ford et al. (1982) used a modeling approach to consider the sensitivity of colony-breeding marine birds to oil spills within the birds' foraging area. Their model consisted of submodels for bird population demographics and foraging behavior. Sensitivity analyses of the population characteristics included in the submodels revealed that the model results were sensitive to values chosen for some of them. The study concluded that the realism of the modeling analysis was hampered by the lack of field observations that would make it possible to specify several of the critical model elements, a conclusion applicable to many modeling studies.

Ecosystem and Oil-Flux Models

As a result of MMS and MMS-related activities, mathematical models have been developed to investigate the biological impact of oil spills and to synthesize and integrate multidisciplinary data. One example is the BIOS (Biological Impact of an Oil Spill) ecosystem simulation model, developed by OCSEAP as part of its eastern Bering Sea environmental

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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impact study. It is a multicomponent model in which most parts of the marine ecosystem and the effects of pollution on organisms, such as fish, are represented in some fashion. The model was used primarily to estimate contaminant concentrations in some fish species and some benthic organisms that result from exposure to oil-contaminated water and sediments and the consumption of oil-contaminated food. Decontamination processes are also included in the calculation of oil-contaminant concentrations in a particular organism. In general, water-column processes (e.g., phytoplankton and zooplankton influences) are included only to the extent they provide food sources for the benthos for the transfer of oil to the sea floor. The model allows for spatial variability due to fish migration and provides an estimate of the amount of contaminated biomass that leaves the model region. The BIOS model and simulations performed with it are described in several technical reports (e.g., Gallagher, 1984; Gallagher and Pola, 1984; Swan, 1984).

Although not funded by MMS, a complex ecosystem model was constructed for the Buccaneer Field study off the Louisiana coast (Fucik and Show, 1981). The model was supported by EPA and NOAA and was developed to aid in evaluating the effects of offshore oil and gas production on the marine environment. Like the BIOS model, the Buccaneer Field model is a multicomponent model. It consists of a system of coupled ordinary differential equations that describe the time-dependent behavior of several biological components and several chemical constituents. Each biological or chemical component is divided into several processes, each of which can be affected by processes in other compartments. The time-dependent model itself is coupled to a hydrodynamic model to obtain spatial distributions.

The biological portion of the Buccaneer Field model consists of 10 components that describe the trophic dynamic relationships in the region of interest. The hydrocarbon portion comprises four chemical constituents—aliphatics, aromatics, branched and cyclic alkanes, and alkyl-substituted aromatics—that are divided on the basis of molecular weight and are acted on by six weathering processes.

The Buccaneer Field model was used to investigate seasonal biomass trends and to describe the flow and storage of carbon between the various biological components. The chemical portion was used to estimate the percentage of total hydrocarbons lost because of weathering. Finally, the combined model was used to obtain average steady-state hydrocarbon concentrations in each biological compartment. Model results implied that the major flow of material in the Buccaneer Field system was through phytoplankton. The short residence time of phytoplankton in the Buccaneer Field region (due to advection), however, indicates that there is only a small probability that contaminated phytoplankton are being preyed on by other organisms in the Buccaneer Field. Nevertheless, contaminated particles might be transported to other locations and incorporated into the food webs there.

Fishery Models

MMS has sponsored the development of two fishery models to assess the effects of OCS activity quantitatively: the Georges Bank model (developed by Spaulding, et al., 1982) and the Bering Sea model (developed by Laevastu et al., 1985). MMS recently commissioned critical reviews of those models by Fletcher (1989) and Deriso (1989). The panel in general agrees with those reviews, whose major points are included in this section.

The Georges Bank model was designed to assess the effects of an oil spill on fishery resources of Georges Bank. It considers only the direct effect of oil on pelagic early life-history stages. It is composed of four submodels: a hydrodynamic model, an oil-spill fate model, an

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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ichthyoplankton transport and fate model, and a fish-population model. The first two submodels have been reviewed earlier (NRC, 1990a). The Georges Bank model is applied to four traditionally important fish species: cod, haddock, sea herring, and yellowtail flounder.

The ichthyoplankton transport and fate model treats pelagic eggs and larvae as passive drifters, subject to local horizontal currents averaged over the top 10 m of the water column. The currents are derived from the hydrodynamic model. The vertical distribution of ichthyoplankton, however, is known to be variable and frequently is often related to such physical features as thermoclines (e.g., Buckley and Lough, 1987). Ichthyoplankton might not be passive with respect to vertically averaged current fields; some species are known to have persistent concentrations in areas where average horizontal currents are strong (e.g., Georges Bank herring, Iles and Sinclair, 1982). The spatial and temporal distribution of the pelagic ichthyoplankton of Georges Bank has been sampled extensively by NMFS. Where the data are available, one can use empirical distributions of ichthyoplankton in oil-spill assessment models, instead of modeling ichthyoplankton transport. Where data are lacking, data on distribution should be collected to verify ichthyoplankton transport models. Where spawning has a wide temporal and spatial distribution (e.g., Georges Bank cod), verification will be difficult.

The Georges Bank fish population submodel assumes a compensatory spawner-recruit function, although no empirical data support this assumption for cod. If the assumption is invalid, the impact of an oil spill will be underestimated. Because the commercially exploited fishery resources of Georges Bank have been depleted by overfishing (NMFS, 1988b), they might not be able to compensate for the additional stress of an oil spill. The maximal effect of an oil spill should have been assessed without the assumption of spawner-recruit function.

The Bering Sea model is more ambitious (not necessarily more useful) than the Georges Bank model. It considers the effect of oil that settles to the bottom on demersal eggs and larvae of Pacific cod and red king crab, in addition to the effects of surface off on pelagic eggs and larvae of yellowfin sole and walleye pollack. It also models the tainting of juvenile and adult king crab, sockeye salmon, and 16 other fish species. The Bering Sea model is poorly documented, so it is difficult to evaluate. Many parameter values are drawn from unpublished sources that are not readily accessible. The initial conditions for juvenile and adult fish biomass are taken from an ecosystem model, “Dynumes” (Laevastu et al., 1985), which is also poorly documented and unverified.

The Bering Sea model shares the two shortcomings of the Georges Bank model. It assumes passive drift of eggs and larvae according to vertically averaged horizontal currents; empirical data on the spatial and temporal distribution of eggs and larvae in this region are inadequate for use in impact assessment or model verification. For most simulations performed with the Bering Sea model, recruitment is assumed to be independent of spawners (having no functional relationship with them); this is equivalent to assuming strong compensation, which can result in an underestimate of the impact of an oil spill. A noncompensatory spawner-recruit relationship is used in a sensitivity analysis, but it is not used as the basis of the primary conclusions from the Bering Sea model.

Drilling Discharges

The Offshore Operators Committee (OOC) and Exxon Production Research Company developed a computer model to simulate the short-term fate of drilling mud discharged into most areas under a variety of environmental and discharge conditions. The model has its origins in the U.S. Army Corps of Engineers-Environmental Protection Agency Dredge Spoil

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Model. It is used to predict the average concentrations of solids and soluble components in the discharged material in the region surrounding the discharge site and the concentration of the solids initially deposited on the sea floor. The OOC mud-discharge model was distributed to OOC member companies and federal and state agencies concerned with offshore-drilling discharge regulation in September 1983 (O 'Reilly et al., 1989). The model has been used extensively in predicting the impact of discharged material on the marine environment.

The mud-discharge model assumes that drilling-mud discharges originate as a jet from a submerged pipe at an arbitrary orientation. The behavior of the discharged material after release is assumed to be characteristic of one of three phases: convective descent of the jet of material; dynamic collapse, which occurs when the descending plume either hits the bottom or arrives at a level of neutral buoyancy, when descent is retarded and horizontal spreading dominates; and long-term passive diffusion, which begins when transport and spreading of the plume is determined more by ambient currents and turbulence than by any dynamic character of its own (Brandsma et al., 1980). Each phase can be represented mathematically, given an appropriate set of assumptions.

The equations that describe the first phase of the discharge, a negatively buoyant plume, are for conservation of mass, momentum, buoyancy, and solids. The conservation equations are in terms of distance along the plume. The mud-discharge model allows for up to 12 discrete classes of particles and a fluid fraction. Each particle class is described by the particle concentration, particle density, and particle settling velocity. The jet itself is described by its radius, its velocity along the jet axis, and its density. The second phase, dynamic collapse, is governed by the same conservation equations, but with the addition of an equation to describe the collapse of the elliptical cross section that is assumed to characterize the plume. In the final phase, the plume has become dynamically passive and is acted on by turbulent diffusion, advection, and settling of the solid particles. The long-term diffusion of the plume in this phase is handled with a LaGrangian scheme of diffusion. Detailed descriptions of the mud-discharge model are given by Brandsma et al. (1980) and Brandsma and Sauer (1983).

The mud-discharge model was verified and calibrated with field studies of discharges into the environment. The most extensive was conducted from a production platform off California in January 1984. In general, the observed and predicted distributions of the particles originating from the discharge agreed. The field study and comparisons between the model and observed distributions are described by O'Reilly et al. (1989).

The OOC mud-discharge model appears to be adequate for determining the average concentration of solids and particles immediately after discharge into the environment. It is not sufficient for determining the longer-term distribution of discharged material; it was not designed to provide more than short-term near-field distributions.

Evaluation of MMS Modeling Efforts

Aside from a major expenditure of resources to develop a fishery model, MMS has made few attempts to use models to consider oil and hydrocarbon effects on marine organisms. In general, the models that have been developed for the latter purpose consist of systems of coupled ordinary differential equations that consider the time-dependent effects of oil contaminants on various organisms. The parameterization of biological processes is based on empirical formulations; in some cases, the “educated guess” approach is used for unknown quantities that are difficult or impossible to estimate. That is not uncommon in biological models; however, the MMS models, such as the BIOS model, have a preponderance of

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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coefficients that are so determined. Consequently, conclusions or predictions derived from the models have little value. In some instances, the biological models have been coupled to hydrodynamic models to obtain spatial distributions. Again, the validity of the circulation model must be considered when assessing the reliability of the model predictions.

MMS has used the models it has developed in two ways: to assess acute short-term effects and to assess chronic long-term effects. Acute effects can be addressed with the oil-spill trajectory models that have been developed for various regions. Those models give the statistical probability related to where the impact of an oil spill will be greatest. That information, when used in conjunction with models of bird or seal distributions, can be useful for short-term management decisions. The effectiveness of the approach is determined by the adequacy of the oil-spill model and the availability of good biological distribution data and measurements of population growth and mortality. The models presented by Ford et al. (1982) and Reed et al. (1987) are examples. As indicated in each of the models, however, values of critical population parameters are not available. In addition, the circulation models on which the population risk models depend are of questionable accuracy (NRC, 1990a).

The assessment of chronic effects entails a different modeling approach. Models that treat couplings between ecosystem components are required, but measurements of the trophic couplings need to be available first. As discussed earlier, MMS has attempted to develop this type of model. The existing models, such as BIOS and Buccaneer Field Study, are complex, cumbersome, and dependent on little known or completely unknown coefficients. The type of data needed to verify their output is lacking. This field needs improvement, especially if MMS desires to focus on long-term effects of OCS activities.

Suggested Citation:"3. Analysis of the Program." National Research Council. 1992. Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology. Washington, DC: The National Academies Press. doi: 10.17226/1963.
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Next: 4. Conclusions and Recommendations »
Assessment of the U.S. Outer Continental Shelf Environmental Studies Program: II. Ecology Get This Book
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Assessment of the U.S. Outer Continental Shelf Environmental Studies Program reviews the ecological studies done by the Environmental Studies Program of the Minerals Management Service.

This program, which has spent $10 million a year on ecological studies in recent years, is designed to provide information to predict and manage the environmental effects of outer continental shelf oil and gas activities. The book considers studies on marine mammals and endangered species, birds, benthic organisms, fisheries, and marine ecosystems and makes recommendations for future studies.

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