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102 4.1.2 Marine Site Evaluation The impact on the ocean resulting from discharged waste depends on the composition and volume of the waste and on the dispersal and transport characteristics of the site selected for disposal. Clearly, the distribution, fate, and effects of waste inputs are governed by the physical, chemical, and biological processes that alter the chemical forms of the waste and their bioavailability. These processes are discussed in detail in Chapter 2. Sewage sludge has been routinely discharged or dumped in the sea at several sites along both the east and west coasts of the United States. From these disposal activities, data bases are available that can be used to begin to evaluate the biological impact of waste disposal in the marine environment. Although our discussion is focused on the impact of sewage sludge disposal, the input of chemical contaminants from the disposal of dredged material and industrial wastes will result in similar effects in the marine environment. 4.1.2.1 Nearshore Disposal Sewage sludge is discharged to U.S. coastal waters either by pipeline (commonly used on the west coast) or barge (primarily used on the east coast). Although the discharge method will generally determine the initial dilution of wastes, subsequent dispersal and transport will depend on advective processes. Along the coast of southern California, the city of Los Angeles discharges sewage sludge (1 percent solids) through a pipe 75 cm in diameter at a depth of 100 m along the rim of a submarine canyon 10 km from shore (Bascom, 1982). Initial dilution of the wastes by 102 occurs, and further dilution and transport of the waste plume are achieved by passive advection and lateral spreading (Brooks et al., 1982). Because of the highly stratified water column at this site, the waste plume usually remains at a depth below the pyanocline. Contaminants of biological concern, such as pathogenic microorganisms, trace metals, and xenobiotic organic compounds, are primarily associated with particulate material, and transport of the sludge particulates is controlled by the same phenomena as is the transport of natural sediments. Only 10 percent of the sludge solids discharged settle on the bottom within 5 km of the
105 dissolved oxygen and accumulation of nutrients in the benthos. Boesch (1982) concluded that the altered benthic community within Christiaensen Basin is better able to cope with organic enrichment than is the indigenous community, but it is less suitable for support of higher trophic levels. Similar changes have been observed in the southern California Bight, and only generalist feeders among demersal predator populations appear to be unaffected by alterations in benthic communities (Allen, 1975; Word, 1979). In addition to the high level of concern about toxic chemicals and pathogens in the marine environment, there is also concern about the release of degradable and nondegradable organic matter and nutrients to the ocean. If these substances are discharged in sufficiently high concentrations to oceanic areas of poor dispersion and mixing energy, depletion of oxygen as a result of the high rate of microbial degradation may occur. Eutrophica- tion of coastal areas from nutrient enrichment may result in changes in species composition and dynamics of marine communities. Mearns et al. (1982) have recently reviewed the effects of nutrient and organic enrichment on marine ecosystems, focusing primarily on the data base available for the New York Bight Apex. Coastal waters of the New York Bight and adjacent estuaries receive high annual inputs of organic carbon, nitrogen, and phosphorus from multiple sources, including barge dumping of sewage sludge and dredged materials, inputs from the Hudson- Raritan estuary, and other coastal and atmospheric inputs (Mueller et al., 1976). In the New York Bight Apex, seasonal and annual variations in productivity and stratification of the water column may lead to periods of low dissolved oxygen or anoxia in the benthos, such as that experienced during the summer of 1976 following a bloom of Ceratium tripes. Nutrient enrichment has also been observed in the Southern California Bight (G. Jackson, Scripps Institution of Oceanography, La Jolla, California, personal communication) On both the southern California coast and in the New York Bight, there are many sources of contaminants and nutrients, so biological effects cannot be attributed to the impact of dumping of sludge alone. Understanding the impact of other point sources is necessary to predict overall degradation of a receiving area. Clearly, the impact of waste discharges depends on the volume and composition of waste to be discharged and on dispersal characteristics at the site of discharge. Low-volume
106 inputs from a small coastal city will not have the same impact as inputs from a large metropolitan area, in either total volume or contaminant loading. These factors must be taken into account in future permit decisions for ocean dumping. 4.1.2.2 Deep-Water Disposal Deep-water disposal of wastes, such as sewage sludge, offers the advantages of greater dilution and dispersion, reducing the potential return of wastes to humans and reducing the potential impact on living resources in nearshore coastal areas. Two deepwater sites have been proposed for receiving sewage sludge: the 106-Mile Ocean Waste Disposal Site (Dumpsite 106) located 106 nautical miles southeast of New York Harbor on the continental slope in the northwest Atlantic at a water depth of 2,000 m; and the proposed Orange County deep-water disposal site located off the coast of southern California at a depth of 300 to 400 m. Dumpsite 106 is typical of slope water regions of the northwest Atlantic, and experience with industrial waste dumping at this site provides a background of mixing and dispersal characteristics of waste inputs. Initial dilution and dispersion of wastes will be similar to those measured for barged wastes in the New York Bight, but the greater depth and proximity to the Gulf Stream ensures greater horizontal transport (O'Connor and Park, 1982). Despite a limited number of investigations that suggest that deposition rates of sewage sludge to deep benthic areas would be minimal, no accurate information exists on the potential deposition rates of sewage sludge to deep sea benthic areas in the vicinity of Dumpsite 106, the extent of the area of deposition, or the resulting impact on benthic systems. Predictive transport models of the pipeline discharge from the proposed Orange County deep-water disposal plan indicate that initial dilution of wastes will be 5 x 102, or greater, depending on the prevailing current regime and the height to which the submerged plume may rise. Further mixing is accomplished by advection and lateral spreading. The most critical difference between other outfalls off the southern California coast and this proposed outfall is its proximity to the oxygen minimum layer, and the potential effects of high biodegradation rates on biota acclimated to a low ambient oxygen
107 concentration (1 mg/L). Brooks et al. (1982), in conjunction with a baseline study conducted by the Southern California Coastal Water Research Project, have developed a comprehensive research program to address the feasibility and impact of this particular disposal option. The paucity of documentation for the disposal of wastes at deep-water sites makes predictions of ultimate biological and/or ecosystem effects difficult to assess; further research is required for evaluation. 4.1.2 Terrestrial Site Evaluation The use of terrestrial and affiliated freshwater ecosystems for the disposal of anthropogenic wastes involves issues that are quite distinct from those of the marine situation. Because of the more intimate contact that humans may have with the wastes, compared, for instance, with contact from open-ocean disposal, the central goal of disposal for terrestrial systems is containment of the various components of the wastes. general, a properly sited terrestrial waste disposal system incorporates an area within which impacts on the natural ecosystem are not considered important and In concern instead is focused on export to other ecological and human systems. As discussed in detail in Chapter 3, such concerns include (1) long-term environmental effects, including contamination of surface or groundwater re- sources, potential threats to human health, and secondary effects on valuable natural and agricultural ecosystems and (2) long-term commitment of land resources. Land spreading and reclamation may also be used as part of ecosystem management practices, such as the use of wastes for nutrient enrichment of park lands to enhance diversity and productivity. There are a large number of terrestrial waste disposal options currently in use (Loehr et al., 1979), such as sludge applications to agricultural land (Council for Agricultural Science and Technology, 1976), sewage treatment by means of cypress domes, other wetlands and silvicultural areas (Ewel et al., 1982), and disposal in landfill and mine reclamation areas (Sopper and Kerr, 1981). Many of the constituents of waste enter surface- water and groundwater systems (Loehr et al., 1979? either through deliberate disposal (e.g., into some rivers and lakes) or secondarily (e.g., from leachate from agri
108 cultural and forest systems). The purpose of this section is not to discuss specific disposal methods or recipient systems but to highlight those aspects of land disposal that need to be addressed. The exports from disposal systems can be categorized as nutrients, organics, heavy metals, and pathogens. The pathways of concern for these include both those linked to other natural systems and those linked to humans. Disposal systems should be designed to prevent direct or indirect contamination of freshwater, groundwater, and estuarine systems, because such systems are characterized by extensive contact with humans, lack of containment, and high concern for system alterations (Ewel et al., 1982). With respect to nutrients, direct enrichment of the disposal area may result in positive benefits, such as increased harvest of food or wood products. This is a key aspect of the application of wastes to managed terrestrial systems in that the resource value (i.e., nutrients) of human activities is recycled. Concern develops with the inadvertent nutrient enrichment of water systems from surface runoff and via percolation of leachate to groundwater. Nitrogen and phosphorus are of primary concern, particularly the movement into ground- water of nitrates and the movement of nitrogen, phos- phorus, and oxygen-demanding organics into surface-water systems (Loehr et al., 1979). The latter is more problematical where climate, topography, and system management practices (e.g., agricultural cultivation) result in significant fluxes of runoff into streams and lakes. Movement of phosphorus into groundwater has been found to be far less significant (National Research Council, 1978~. For various terrestrial disposal systems, transport of toxic organics and heavy metals into both surface- and near-surface water systems remains an issue of concern, with respect to impacts on other natural systems and particularly with respect to pathways to humans. It is beyond the scope of this section to treat this topic in detail; rather, we will simply indicate that the waste stream must be characterized with respect to these toxicants and that their physicochemical characteristics and those of the environment are critical to determining the fate, transport, and effects of the toxicants. Transport of pathogens to humans must be addressed for any terrestrial system. Potential pathways include direct consumption of food products grown in waste-amended
110 population- and community-level effects occurring within the area under primary impact rather than on processes, because of the limited spatial extent of the population perturbation relative to the spatial scale of most ecosystem processes. When considering the effects of waste disposal at population and community levels, the first concern is potential elimination of a species, either through direct toxicological impacts or indirect effects, such as loss of habitat or reduction in some essential resource base. The issue of the spatial extent of the impacted area versus the spatial range of the species is critical. Further, for many species the area of concern includes the range for early life stages (e.g., nesting or spawning areas), which is smaller than the total geographical range for the mature stages. Similarly, the loss of a particular habitat that is both limited in its general occurrence and spatially of the same scale as the waste-impacted area presents a problem that must be addressed, as does the elimination of unique biotic communities. Of less dramatic concern is the alteration of com- munity structure. Community structure continually changes, even without significant anthropogenic pertur- bations; thus, alteration in the community structure per se may not represent a major problem. The situation becomes important, however, if such community alterations are major in spatial extent or unidirectional change and in the relationship and distribution of the constituent species. To evaluate these alterations, one must look at the interrelationships among the species. There may be some critical species whose presence is required for a significant part of the overall community to exist. Loss of the critical species from a location will result in concomitant indirect losses or population explosion of other species. Similarly, there are critical groups of species, i.e., a number of species may function redundantly within the system. The loss of all of them would result in the loss of their critical function in the overall ecosystem. Another class of indirect effect that must be con- sidered is the impact on some species that have par- ticular aesthetic or economic value. For example, pollution-induced reduction in benthic habitat could result in depletion of fisheries, even though the fish were not directly affected by the pollution.
111 A final issue that needs to be addressed is the recoverability of the systems under impact. Rates of recovery of defaunated or defoliated areas depend on the rates at which the area becomes habitable again and on the rates of recolonization by the biota. These values depend to a large degree on the spatial scale of the impacted area. The recovery of a small area surrounded by undamaged systems is more rapid than is recovery of large impacted areas that have relatively fewer sources of colonizers. In summary, the aspects of ecosystems that must be considered when evaluating waste impacts range from direct effects on individual species and effects resulting from interspecific interactions to effects on community structure and concomitant functional relationships. These aspects are overlaid by consideration of spatial and temporal scales. These are the types of information and understanding required, but it is quite another matter actually to attain them. For instance, while direct impacts on heavily affected areas may be readily discernible, effects of longer-term, more widely disseminated lower-level stresses are generally more difficult to detect. Such chronic stresses can affect a species in more subtle ways (e.g., behavioral changes versus immediate mortality) and often involve more indirect mechanisms. The response time is longer, and distinguishing stress-induced responses from normal environmental fluctuations and spatial heterogeneities is especially difficult. Temporal relationships, such as the one between biodegradation and accumulation rates, become important. Even more difficult to understand are synergisms, in which chronic pollutants have a greater impact in combination than separately. Each of these aspects contributes to the degree of uncertainty inherent in ecological evaluations. The significance of the uncertainty that remains after the ecosystems have been realistically characterized is a major issue in selecting among disposal options. This is particularly true since the uncertainty in predicting ecosystem-level effects of waste disposal includes not only a component related to the amount of information that has been collected about a system but also a component of intrinsic unpredictability. Further, the degree of uncertainty remaining even after a system is reasonably well studied varies from one ecosystem type to another.
112 4.2.2 Effects on Species The ultimate impact to be avoided is the actual extinction of a species. Species extinctions have accelerated at an alarming pace in recent years, in most cases from the destruction of critical habitats. Such habitat destruction from sewage disposal is unlikely in open-ocean systems because the benthic species under impact have large ranges and, usually, good dispersal capabilities relative to the areas under impact. The degradation of coastal wetland habitats could be more serious, especially on the West Coast of the United States where wetlands are smaller and more isolated than East and Gulf Coast wetlands. The few remaining West Coast wetlands are refuges for several endangered insects, vertebrates, and plants (Onuf et al., 1978). Indiscriminate disposal of sewage and other materials in coastal wetlands should be avoided. Bastian (1981), however, suggests that both freshwater and marine wetlands could be effectively managed for waste disposal without deleterious effects on the ecosystem. The U.S. Environmental Protection Agency is currently developing guidelines for wetlands management practices that could be applied to the effective and environmentally compatible use and innovative treatment of wastewater in existing wetlands as well as to the establishment and management of artificial wetlands created for the primary purpose of wastewater treatment. Landfill practices in terrestrial ecosystems can eliminate critical habitats of endangered species, and such elimination must be guarded against. At the same time, indirect effects on endangered species are also possible. These situations could include poisoning or the eutrophication of lakes, ponds, other surface waters, or groundwater in such a way that isolated critical habitats (including, e.g., caves) could be affected. In summary, species extinctions could result from sewage disposal if critical habitats are destroyed or seriously altered. This is unlikely for offshore systems; it is possible, but relatively easily guarded against in terrestrial systems; and it is a very real danger in West Coast wetlands. It is important to emphasize that species extinctions are not adequate indicators of damage. Many important changes can occur without species extinctions. Further- more, there is a tendency to be concerned about a small subset of species that are conspicuous or important to
115 reduction of these habitats by man has threatened many species, and although these habitats enjoy certain resilience, they should be protected from further perturbations, especially the West Coast remnants. Valid generalizations about the recoverability of terrestrial habitats are difficult cases vegetation can be replanted, , to make. In many but this may be more difficult than it appears as other opportunistic species often resist invasion, and natural succession can be relatively slow. In practice, the consequence of most landfill operations is residential development, and this retards natural succession almost indefinitely. In summary, relatively shallow (<60 m) offshore soft-bottom benthic communities may have the highest rate of succession and recovery from waste disposal. Many terrestrial systems can be replanted and fairly quickly recolonized by animals, but it is unlikely that landfill operations will follow this procedure. 4.2.4 Productivity Changes Wastes such as sewage sludge can change biological productivity in dumping areas either by increasing plant nutrients and thereby stimulating photosynthesis or by direct input of organic matter. Sufficient quantities of waste can, of course, completely bury and smother the biota in any environment. In waters with restricted circulation (such as in shallow and semienclosed basins, soils with high water tables, estuaries, and small lakes), direct organic additions or increased primary production can result in anoxia. In lesser amounts, organic enrichments can change the composition of communities. Generally, enrichment results in a reduction in diversity accompanied by an increase of biomass in soft-bottom marine systems (Pearson and Rosenburg, 1978), though in some cases rip a . New Enaland salt marshes) increased productivity ~ _ · ~ , ~ ~ ~ increases diversity by enhancing the abundance of rare animals and increasing "evenness. Additions of nutrients increase primary pronucc~v~`y in many systems. In experiments at the Marine Ecosystem Research Laboratory (MERL) in Rhode Island, high nutrient _ a _~.. ~ _ _ additions to shallow marine mesocosms Increases Ably ~u- plankton productivity, decreased benthic species numbers, and had little effect on numbers of copepods in the zooplankton (Grassle and Grassle, in press; Nixon et al.,
116 in press). Nitrogen addition to salt marshes increases primary production, but more important is the increase in nitrogen content of the grasses, which subsequently increases production of herbivores and detritivores and enhances the attractiveness of the fertilized stands to more mobile herbivores, such as geese and voles. Altera- tions in the relative abundance of insect herbivores in comparison with those in unfertilized marshes also occurs (Vince et al., 1981). In any nutrient-limited system, one could expect some species to be better able to make use of added nutrients than others, so that changes in plant community com- position would occur, and the changes would depend on both the duration of the additions and the nutrient levels achieved. Nutrients in sludge, along with the water in it, would drastically change the composition and productivity of desert and semidesert communities. Moderate additions to forests in humid regions would have less drastic effects on the plant communities themselves, although there could still be large changes in other components of the community, such as the abundance of insect herbivores. 4.2.5 Transport of Waste Constituents It must be decided whether waste should remain concentrated locally in the environment into which it is placed or be dispersed throughout a greater volume (i.e., diluted), thus contaminating neighboring systems. Dilu- tion can reduce the concentration of potential toxicants below the danger level but also make it impossible for complete biological decomposition to occur (Rubin et al., 1982). Dispersal of a substance makes it more difficult to recover, should that become desirable. Thus, the strategy of dilution markedly reduces the capability to mitigate undesirable consequences. Fluid transport is responsible for most movement of materials between systems. Air transport can move materials throughout large areas as the Sea Air Exchange (SEAREX) studies demonstrate, but the amount and con- centrations arriving at sites far from the source are small. Water is more effective and can move much larger amounts. Transport of contaminants to downstream systems must obviously be considered in any evaluation of aquatic sites.
117 In the case of marine disposal, once materials have reached the deep oceans, transport would ordinarily be expected between deep sites, often within the same general depth contours and therefore within one depth-controlled ecosystem. In shallow waters, movement can easily occur across system boundaries. Materials could move inshore into estuaries transported by bottom currents, or they could be moved offshore by turbidity currents. On land, surface waters can distribute pollutants over great linear distances and, eventually, into estuaries. Fluxes of waste components into groundwaters can also occur, and once the groundwater is contaminated, the potential exists for exceedingly long residence times of materials. One must also consider the possibility of an organism moving a contaminant, especially a pathogen, from one system to another. If a parasite or virus introduced with a waste survives or even multiplies within a motile organism, it could significantly contaminate a system not being contaminated directly by the dumping. Populations of fish that migrate great distances along a coastline may result in contaminated organisms being harvested from uncontaminated areas 4.2.6.1 Uniqueness . 4.2.6 Habitat Types Destruction of unique habitats and communities spatially separated from similar habitats by distances that create barriers to dispersal and recolonization should be avoided. In the marine environment, habitats of par- ticular concern include coral reefs, deep-sea hydrothermal vent communities, seamounts, kelp forests and other sites of high recreational use, and communities on the walls of some submarine canyons or islands. Estuarine communities, although often separated from each other by considerable distances, are made up of some species with efficient dispersal mechanisms so that there is little or no evidence of genetic differentiation between individuals from widely separate estuaries (Gooch et al., 1972; Morgan et al., 1978). Other so-called cosmopolitan species, however, may be shown in the future to be genetically distinct in different estuarine systems within one climatic zone. Deep-sea communities in general appear to comprise species with broad geographic ranges at certain depths.
119 organic enrichment in shallow benthic communities, Pearson and Rosenburg (1978) suggested that such successional stages include an initial zone of a few, small, rapidly breathing short-lived species with high genetic variability, followed by gradual changes in population with wider ecological and reproductive characteristics but lower genetic flexibility and contributing to increased community complexity. In terrestrial environments the same principles apply. There are numerous examples of successional changes in terrestrial ecosystems as well (McIntosh, 1980). Suc- cessional properties and rates vary widely in different ecosystems, but once disposal is abated, natural suc- cession should lead to recovery. Isolated rare habitats, however, may not be readily replaced by natural succession as propagules may not be readily available for coloniza- tion. These are exemplified by springs, especially in arid regions, isolated wetlands, rock outcrops such as limestone in regions of acid soils, and desert ponds. Restoration of unique habitats in terrestrial and aquatic ecosystems may require artificial reclamation as propagules for recolonization are not readily available. Creation of artificial wetlands on the West Coast (Race and Christie, 1982), restoration of mangrove communities (Teas, 1977), and the restoration of plant communities in many terrestrial environments, ranging from high alpine to desert ecosystems (Cook, 1976), are but a few examples of successful restoration programs. In practical terms, the uniqueness of a habitat may consist in its being the last fragment of the natural world surrounded by a greatly modified landscape. Urban ecologists have studied the importance of providing avenues for dispersal of city-dwelling fauna and flora by preserving the contiguous distribution of patches in the natural environment. Furthermore, social scientists have long appreciated the social importance of parks and natural sites in urban areas. 4.2.6.3 Nursery Grounds It is apparent that areas that are intermittently used as nursery or spawning grounds should not be used as sites for waste disposal. Such areas include banks where hydrographic conditions promote concentration of developing embryos at certain times of the year (e.g., Georges Bank), benthic areas where spawning occurs, and
120 estuaries that act as nursery areas for many resource species (e.g., penaeids, blue crabs, salmonids). 4.2.7 Monitoring Ecosystem Effects Monitoring programs are an important component of ecosystem analysis in order to provide time-series data sets of long-term, unexpected changes in the ecosystem as a result of waste disposal. Ecosystem effects must be examined directly in the field by following the complete system, so that unsuspected interactive or synergistic effects can be detected. The study must be designed by researchers familiar with the systems at the site. Laboratory and field process-oriented studies would have to be conducted in parallel with monitoring of the system to detect causes for any changes observed in the system. The most difficult aspect of the research would be the selection of adequate control sites, which should be similar to the dump site in all aspects except for being subject to waste inputs. Sites similar in climatic and hydrographic conditions, and, with regard to sediment or soils, larval or propagule supply, predators, and productivity, for example, will usually mean that such sites are close together. But the water or air must not carry pollutants from the experimental site to the control site. An upstream positioning from the dumpsite seems logical but may be difficult to achieve with certainty. This is one reason that monitoring of the pollutant concentration must be done along with the biological measuring. Furthermore, one must be especially aware of the potential for storms or other rare events to spread wastes into the control sites. 4.2.8 Health Effects--Pathogens In determining possible pathways that pathogenic organisms in wastewater sludge will follow from their point of disposal back to humans, one of the first considerations is the characterization of the dis- tribution of such pathogens in sewage wastes. In general, sewage influents contain four broad groups of human pathogens: viruses, bacteria, protozoa, and helminths (Table 4.1). The occurrence of most of these microbial pathogens is dependent on the incidence of disease in the discharging population. The concentration
123 Cabelli et al., 1982), and disease outbreaks caused by wastewaterborne Norwalk agent virus have been documented (Baron et al., 1982). Most of the evidence associating disease with wastewater-contaminated environments has been obtained from studies conducted in nearshore marine coastal waters or freshwater areas. The translation of these data to long-distance ocean outfalls or waste dump sites depends on the availability of information concerning two critical factors: (1) the ability of pathogens to persist and to replicate in marine environments and (2) an understanding of potential transport routes back to nearshore areas. The evidence is clear that human pathogens, including protozoa, bacteria, filamentous fungi, yeasts, viruses, and parasites are present in sewage sludge and, very often, in dredge spoils as well (see Table 4.1, Alderslade, 1981; Sawyer et al., 1982). These organisms survive and persist, and as methods for isolation and outgrowth are improved, they are recovered with increasing frequency from water, sediment, and macrobiota samples from the Philadelphia and New York dumpsites (Table 4.2). Epidemiological evidence, however, has only linked a few of these pathogens to disease outbreaks in the United States. A vexing issue is that of transport of these pathogens from the dumpsite regions and regions under impact from the dump to nearshore areas and, ultimately, to humans. Unfortunately, the hydrography of the offshore dumping areas has not been sufficiently described to make possible careful estimates of potential risks. This is especially so since measures of ocean currents (i.e., current speed and direction) and related physicochemical parameters of the waters do not, alone, define risks completely. For example, most microorganisms in aquatic systems tend to adhere to surfaces and to colonize particulates and organic aggregates. The particulates and aggregates provide protection against adverse environmental conditions, thereby enhancing survival and long-term persistence in the environment. Furthermore, the transport of pathogens attached to particulates and aggregates is different from that of free cells in the waker column. and this may influence pathogen transmission Sinking rates and transport vel- ocities need to be known to determine whether transport of pathogens will occur from the dumpsites to areas of human activity and hence into contact with humans. to shellfish stocks.
124 TABLE 4.2 Pathogens Documented to Occur in the Anacostia River, District of Columbia, and in the New York Bight Concentrations per 100 mL of water Isolates Anacostia Riv, New York Bight Total viable count 7 2 x 106-2 x 10' 700-76,000 Total coliforms 3,000-28,000 4-800 Total fecal coliforms 100,4,900 0-90 Total anaerobic count 0-10,000 0-43,000 Aeromonas spp. 1,000-50,000 0-10 Bacteroides spp. + Clostridium spp. + + Enterobacter spp. + Escherichia cold + + Klebsiella spp. + + Salmonella spp. Vibrio cholerae Vibrio parahaemolyticus Group F Vibrio + + + + + + o o + + NOTE: +, detectable levels present; 0, not detected.
126 Because of costs and lower frequency of occurrence in sewage, pathogens themselves are, in general, not the subject of bacteriological surveys. Instead, indicator organisms are enumerated, such as E. cold and related members of the coliform group, including Klebsiella and Enterobacter. For nearshore waters and estuaries, the coliform group has provided a workable, if not totally reliable, index of sanitary quality. The extensive work of Cabelli and colleagues (Cabelli, 1980) has been focused on evaluating various indices for establishing human health criteria in recreational waters. A strong correlation exists between the incidence of gastro- intestinal symptoms and enterococcus densities, but poor correlations exist between disease incidence and total coliform and Clostridium perfringens densities. A major, well-recognized, documented shortcoming of the coliform (bacterial) indicator is that it does not provide an estimate of the presence of human pathogenic viruses. There have been documented cases of gastro- enteritis induced by Norwalk and Norwalk-like viruses as a result of ingestion of contaminated shellfish harvested from waters judged to be safe for humans according to coliform counts. The currently accepted standard--70 total coliform per 100 mL of water, with not more than 10 percent of the samples exceeding 230 coliform per 100 mL--was established many years ago (circa 1939). This standard was not based on epidemiological evidence, and therefore it has little value with respect to predicting risks to the health of consumers of shellfish that have been exposed to sludge or sewage effluents. Fecal coliform indices are also used to assess shellfish contamination, but the relationship of these indicators to nonbacterial pathogens, is equivocal at best and nonexistent at worst. The relationship in offshore waters is totally unclear, and data are only now being gathered at the Philadelphia and New York dumpsites. If the relative merits of ocean versus land disposal of sludge is to be properly evaluated with respect to health risks, development of improved methods for identifying indicator and pathogen densities in shellfish, sediments, and water will be necessary. 4.2.8.2 Pathogen Problems Associated with Land Disposal The application of wastewater sludges to land creates a potential hazard to human health. The transport of
130 surfaces is the easiest route of uptake by marine organisms, uptake through ingestion of food organisms and particulate matter are the most important ecological routes of transfer (G. W. Bryan, 1980). Bioaccumulation of metals in the marine environment may be further complicated by the physiological state of the animal, environmental conditions, and the ability of an organism to regulate metal uptake (George, 1982; Phillips, 1977). The role of bacteria in bioaccumulation has been demonstrated (Nelson et al., 1975), and effects on the food chain have been reviewed. Both metal and organic toxicants are taken up by bacteria, and the process may provide a rather significant mechanism for food-chain biomagnification and transfer. Marine animals differ in their capacity to store, remove, or detoxify metal contaminants. Storage may involve deposition into tissues, skeletal material, and concretions or within intracellular matrices (George, 1982). Removal may take place via excretion or the production of particulate products, such as feces, eggs, and molts. G. W. Bryan (1979, 1980) classified organisms as to their relative metal regulatory ability: (1) where the contaminant is excreted at a rate proportional to body burden, (2) where the contaminant is stored rather than excreted, and (3) where an organism excretes most of the excessive input. Crustaceans and fish are the best regulators, and essential metals such as zinc and copper are better regulated than nonessential metals such as mercury and cadmium. Certain metals may be detoxified by binding to metallothionein proteins in fish (Jenkins et al., 1982) and similar heavy-metal binding proteins (HMBP) in crustaceans and molluscs (Jennings et al., 1979; Noel-Lambot, 1976; Noel-Lambot et al., 1978; Roesijadi, 1981; Roesijadi et al., 1982). Both proteins are thought to exert their protective effect by sequestering free metal ions and partitioning them away from potential sites of toxic action (Jenkins et al., 1982). If the binding capacity of metallothioneins or heavy-metal binding proteins is exceeded, toxic effects of metal contaminants may be induced (Lee et al., 1980). George (1982) suggested that detoxification can also occur through compartmentation within extracelluar or particulate intracellular structures or blood cells. The transport of xenobiotic compounds, such as polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyl compounds (PCBs) is also linked to particulate
131 transport, and thus such compounds tend to accumulate in sediments (Boehm et al., in press; Bopp et al., 1982). Bioaccumulation of lipophilic organic contaminants (PAHs, PCBs, or other chlorinated hydrocarbons) by marine organisms is dependent on both chemical factors, such as solubility, adsorption-desorption kinetics, and the octanol-water partition coefficients of specific com- ponents, and biological factors, such as the transfer of such compounds through food chains and the amount of body lipids in exposed animals (Neff, 1979). The availability of xenobiotics to marine organisms and their effects on those organisms are dependent on chemical and microbial processes within the sediments, including sorption/ Resorption reactions and the production of potentially more toxic metabolites from degradation (Gibson, 1981). Uptake of PAHS and PCBs by bacteria and phytoplankton may further enhance the transfer to higher trophic levels (Iseki et al., 1981). In both vertebrate and invertebrate systems, including mammals, fishes, crustaceans, and polychaetes, biotrans- formation of PAHs and PCBs may occur through cytochrome P450-mediated mixed function oxygenase (MFO) reactions. Such transformations result both in the production and excretion of more soluble, potentially more toxic metabolites (Stegeman, 1981). Some metabolites of xenobiotics have been shown to be carcinogenic, mutagenic, and teratogenic, and their potential long-term effects are of significant concern. Bivalve molluscs have only a limited capacity for biotransformation, and thus xeno- biotic compounds will accumulate in their tissues and be directly available for human consumption. Recent studies of the incidence of tumors and other h istopathological conditions in demersal fish from the Duwamish River and Hudson River estuaries as well as the Southern California and New York Bights have suggested a possible link of chronic xenobiotic inputs and the increased incidence of such conditions (McCain et al., 1978; Perkins et al., 1982; Sindermann, 1980; Sinderman et al., 1980; Smith et al., 1979; Stegeman, 1981). Toxic effects of xenobiotics include impairment of reproduction, growth, and development (Califano, 1981), and potential effects on populations cannot be ignored. 4.2.10 Summary It is understandable that those who must regulate should seek from natural scientists a single index that will
132 indicate whether a population, community, or ecosystem has suffered irremediable damage. However, no such index exists, nor can one be devised. There is, on the other hand, no substitute for a functional understanding of how particular communities respond to change; and this understanding, though not perfect, is already available for some communities and should be used. For others, developing such understanding will require further research. Table 4.3 summarizes the biological concerns for different types of environments. The numbers should not be added in either the columns or rows; they represent individual estimates that must be considered together, as a framework useful in biological aspects of decision making. 4.3 INFORMATION NEEDS The objectives of waste disposal research are to (1) improve management schemes, (2) refine the types of remedial actions via better understanding of the natural recovery processes, (3) define pathways and fates of pathogens and toxic material, and, most importantly, (4) better understand the components and workings of the ecosystems to further improve and define the research/management goals and practices. Specific information gaps that currently exist are as follows: . An understanding of functional responses of ecosystems under impact is essential if we are to identify the possible routes by which toxicants and pathogens can reach humans and if we are to be better able to predict the outcome of chronic inputs to affected communities. This understanding, however, must be predicated on improved knowledge of community structure, such as what species are present in the ecosystem, their life histories, and the demographics of the important species, as well as the potential recovery rates of impacted ecosystems. Such information can be obtained both through the use of in situ long-term studies and experimental microcosms as parts of natural ecosystems. · The contention in this chapter that most deep-sea species have wide geographic ranges is based on little evidence. This is especially obvious from an examination of species lists from some recent investigations of
133 deep-sea sites. They contain numbers of unidentified and unnamed species and undifferentiated groups of species making it impossible to compare results from different laboratories and different sites. · As many contaminants are associated with particulate matter in the marine environment, improved understanding of hydrographic conditions, particle behavior, resuspension, and biological modification of particle fluxes is essential. This would include an understanding of the partitioning of contaminants between water and sediment particles, especially as this is affected by the activities of organisms in ventilating, irrigating, and passing material through their guts. · Increased efforts are needed to estimate and . quantify the relative contributions of pollutants from different sources in areas receiving multiple inputs, especially in shallow estuaries and coastal areas near large metropolitan centers. · The survival and persistence of human pathogens (viruses, bacteria, fungi, protozoa, and helminths) in seawater are uncertainties that need to be addressed, in addition to identifying the parameters such as nutrient loading, salinity, temperature, and pressure that influence survival and persistence. The relationship between pathogens, notably viruses, and particulates must be established to determine survival and transport of pathogens to areas of human activity. This would include development of decay models for particle-associated bacteria and viruses in aquatic environments. · Criteria on health effects for shellfish- associated disease must be defined. These should include the development of more specific bacterial indicator methods to monitor potential health hazards associated with marine sludge disposal sites. · A similar data base on the survival and mobility of pathogens in soils must be established. This should include the development of methodology to differentiate human and animal contamination in an impacted ecosystem. Attention should also be focused on the development of predictive models to evaluate pathogen contamination of groundwater supplies and land crops. · A better understanding of surface and subsurface drainage patterns from land disposal sites is needed to predict the export of toxicants and pathogens from disposal activities and their potential accumulation in groundwater and surface-water resources.
135 ·~ 11 ~.. U]o us ~ in ~ ~ ~C .. en ~ ~o ~·- o ~ ~·- v ~3 · US UP ~ o ~·- ·- a, ~U] 0 ~a, o ·- ~ a) ~In ~ O o o ·- a ~ ~ ~ ·- ~1 ~ 11 ~a) ~ ~ Q C ~·- O ·- ~ =,' i- , ~· - Up ~ Up · ~ ~ ~·- ·- Q Q ~ O - O ~ ·- 0) 0 ·- ~·- Q Q ~ ~ ~O ~O O In us ~ ~ in O O ·~-- V-- ~ ~ ~' ·- Q. ~Q In ~ ~ ~ ~C ~.- O O ~·~-- vt ~·- ·- ~ 3 G) ~ ~3 S ~·- o i4 ·,' U] ~ ~ . ~2 11 lU a) v' ~·- ~- · ·~ ,.~: ~ ~ ~ =: a) ~ ~n me U~ ~ ~-1 Ln ~ ~ ~0 ~ 3 ~ ·- ' ~ ~Q ·e ·. -= ·,' 5: ~ ~, ~ ~ ~.- e. U] O ~ ·- ~U] ~ ~·- 11 ~- -- ·- ~ln ~ ~ ~ .°, ~ ~ ~ 8 o ~ 3 · ~ ~ U ·,1 ~ ~ ~ ~ O O O C a. ·- ~ ~ GS r~ O ~1 ·- U] V] ~ ~·- U, ~) ~ ~ O O I U] ~ ~ ~ ~ 1 ~ ~1 X O ~ I ~·- ~ 1 ·- 11 4, ~ · ~ 1 3 Q -v' _ u? ~n I c ·'l ~ O ~ ~ 0 qJ ~ ~c o~ P ~ O ~ ~ ·- 11 ~ 11 ~ ~ ~ ~ 1 U] O ~ U] ~ ~ ~ ~ ~C ~ ~ ~ ~ C O ~ ~ ~ ~·- ·- ~ ·- ~ . ~ . t, ~ 0 ~ ~ ~ ~ ~ ~ ·Q~ ~ ~- ~ . O ~ Q~ ~ ~ ~ ~ ~ O ~ ~ ~ ~ ·~ O ·~ ~ ~g ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ O O :~: % ~ ~·- ~n v ~u~ ·,1 .,, 0e .,.
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