Freshwater Ecosystems Revitalizing Educational Programs in Limnology (1996) / Chapter Skim
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3 Contemporary Water Management: Role of Limnology
3 Contemporary Water Management: Role of Limnology
Pages 65-117
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From page 65... ...
The chapter divides problems in aquatic ecosystems according to whether they originate from modifications in the watershed or physical characteristics of the water body; from changes in the water's chemical composition; or from alterations in the ecosystem's biological communi 65
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From page 66... ...
These physical changes can have subtle or dramatic impacts on the structure and functions of aquatic ecosystems, depending on the severity of the change. In many cases, the impacts are caused by excessive diversion of water from a stream for crop irrigation or other water supply purposes to the extent that so-called in-stream uses of the water (for example, maintenance of fish populations)
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From page 67... ...
The concentrations of dissolved oxygen in the lower water column of reservoirs may be low or zero in some instances, hampering the development of fisheries or altering the native fauna below dams (Petts, 1984~. Further, water released from dams is likely to have a lower sediment content than water entering a reservoir (Andrews, 1991)
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From page 68... ...
Increased mercury levels have led to losses of commercial, recreational, and subsistence fisheries. The increase appears to be largely the result of low oxygen concentrations caused by the decay of flooded vegetation.
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From page 69... ...
o 3.5 cn o 2.5 ._ an o O 1.5 I a)
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From page 70... ...
Wetlands also function as filters, transformers, and sinks for materials delivered to them by human activities, thus improving water quality. For instance, they can filter 60 to 90 percent of suspended solids from wastewater and as much as 80 percent of sediment in runoff from agricultural fields (Richardson, 1989~.
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From page 71... ...
SOURCE: Paul H Glaser, Limnological Research Center, University of Minnesota.
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From page 72... ...
. How will global warming affect wetlands, particularly peatlands, and vice versa?
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From page 73... ...
Forests and grassland have been transformed to agricultural fields or urban pavements as societies have established themselves around water bodies; forest ecosystems have been replaced with tree plantations designed to meet human needs for timber. Studies by limnologists and their fellow water scientists have provided valuable insights about impacts of human development on water bodies.
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From page 74... ...
Although scientists who believe that global warming is occurring or will soon occur outnumber the dissenters, there is disagreement about how much the temperature might increase and how fast (American Society of Limnology and Oceanography and North American Benthological Society, 1994; Houghton et al., 1995~. Despite this disagreement, it is widely accepted that substantial changes in the temperature of the earth are likely to have significant effects on inland aquatic ecosystems (see Box 3-2~.
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From page 75... ...
These many uncertain factors will have to be better understood before the timing and extent of global warming can be predicted. Limnological research can help to reduce these uncertainties.
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From page 76... ...
. In lakes, longer ice-free seasons, warmer water temperatures, and deeper thermoclines may cause dramatic increases in habitat warmth (measured as degree-days)
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From page 77... ...
on organisms and biogeochemical processes in aquatic communities. CHEMICAL CHANGES IN AQUATIC ECOSYSTEMS Humans have long used the water bodies beside which they have settled as receptacles for their wastes.
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From page 78... ...
For example, state water resource managers identified agricultural runoff as a cause of impairment of 49 percent of the damaged lakes, rivers, and streams they assessed; Hey identified urban runoff as a factor in He decline of 24 percent of damaged lakes and 10 percent of damaged rivers and streams (Environmental Protection Agency, 1994~. Three of the major impacts of excessive waste loadings to surface waters are loss of dissolved oxygen, cultural eutrophication, and buildup of toxic compounds.
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From page 79... ...
/ Which is a sink or loss term/ and atmospheric reaerahon/ which ~ a source arm. The outwit of this equation ~ Mown as We Oxygen sag curved' because the oxygen concenbabon decreases downstream of a waste discharge and/ urger downstream/ increases again once We waste is biodegraded gee Fox 3-3 and Figure 3-2\ Although
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From page 80... ...
PAUL METRO PLANT ,, Water Quality // Guideline (1928) NEWPORT GREY CLOUD LOCK & LOCK DAM 2 DAM 3 SAMPLING SITE · 1926 ~ 1934-1938 0 1942-1955 ~ 1956-1965 x 1966-1978 v 1979-1987 FIGURE 3-2 Mean August dissolved oxygen concentrations In the Mississippi River below St.
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From page 81... ...
Similarly, the states reported that dissolved oxygen depletion is a major source of impairment in 2 percent of assessed rivers and 3 percent of assessed lakes (EPA, 1994~. The work by river specialists and other aquatic scientists has been a major factor underlying the success of the Clean Water Act in addressing the dissolved oxygen depletion problem.
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From page 82... ...
the relative importance of internal nutrient cycling versus external nutrient loading in causing or maintaining symptoms of eutrophication; and (5) the degree to which controlling external nutrient sources would result in rapid improvements in water quality conditions or whether additional in-lake restorative measures would be needed for most lakes.
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From page 83... ...
A well-known example of a nitrogen-limited inland lake is Lake Tahoe in the Sierra Nevada.
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From page 84... ...
As nutrient control measures took effect on municipal effluents, the relative importance of contributions from nonpoint sources began to rise. By 1980, nonpoint sources contributed approximately 95 percent of the total nitrogen load and 98 percent of the total phosphorus load to surface waters (van der Leeden et al., 1990~.
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From page 85... ...
and eutrophication (in nitrogen-limited waters such as Lake Tahoe and the Baltic Sea) result (Rosenberg et al., 1990~.
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From page 87... ...
For example, limnologists cannot predict which specific assemblage of blue-green algae will result from specific nutrient loadings, nor can they predict which other algae will replace them when nutrient levels are decreased or biomanipulation is used. Accumulation of Toxic Pollutants Municipal and industrial waste discharges, urban runoff, and agricultural runoff all contain trace concentrations of toxic compounds (Novotny and Chesters, 1981; Lazaro, 1990~.
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From page 88... ...
Many limnological studies have shown that in the passage up food chains, organochlorine compounds can accumulate in predatory fish or fish-eating birds and mammals at concentrations up to 10 million times greater than those in lake water. Even in very remote areas, the concentrations of organochlorine compounds in fish and marine mammals can be high enough to require that consumption by humans be limited.
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From page 90... ...
(see Box 3-8~. If neither soils nor aquatic sediments can neutralize acid rain completely, the pH of the lake or stream water declines, causing a variety of deleterious effects.
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From page 91... ...
CONTEMPORARY WATER MANAGEMENT 91 predict that recently imposed controls on sulfur oxide emissions will reduce acidification damage only to about half of that caused by emissions at early 1980s levels. Limnologists have shown that the degree of biological change occurring in aquatic communities as a result of acid rain can be related clearly to the degree of acidification (Brezonik et al., 1993)
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From page 92... ...
during the 1980s, information about the full range of ecosystem effects of acid rain is lacking for nearly all groups of aquatic organisms other than commercially important fish. Therefore, it still is not possible to predict with great accuracy the long-term consequences for the functioning of aquatic ecosystems of the alterations brought about by acid stress, and further research is needed.
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From page 93... ...
The deleterious effects of these metal and synthetic organic compounds upon inhabitants and users of aquatic ecosystems are less well documented than those of acid rain. However, in the case of mercury and PCBs, warnings have been issued in more than 30 states concerning the consumption by humans of fish from numerous lakes and rivers, including many in the Great Lakes states.
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From page 94... ...
Many bioaccumulate to such high levels that they are toxic to the end-members of aquatic food chains. In the case of mercury, rules of the U.S.
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From page 95... ...
In parts of the state, this standard may be inadequate because in some lake waters with mercury levels of only 2 ng per liter, the concentration in fish exceeds 0.45 ppm three times the consumption advisory for pregnant women. Larger, older predatory fish at the top of the aquatic food chain are of particular concern
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From page 96... ...
"Vacation" refers to those who eat the particular fish species only during short vacations; "season" refers to those who consume the fish seasonally; and "annual" refers to those who consume the fish year-round. SOURCE: Minnesota Department of Health, 1994.
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From page 97... ...
, have been centrally involved in the study and solution of problems caused by acid rain and airborne toxic compounds. Table 3-1 chronicles some of the key scientific discoveries concerning the effects of acid rain and toxic air pollutants on aquatic ecosystems.
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From page 98... ...
1995 Muir et al. Showed the degree of acidification of English lakes to be related to substrate geology Recognized the relationship among acid rain, surface water acidity, and disappearance of fish in Norway Reported biological magnification of DDT in aquatic food chains Indicated atmospheric precipitation as an important source of trace metals in Lake Michigan Showed a reduction of biodiversity in phytoplankton, zooplankton, and fish in acidified Swedish lakes Found atmospheric deposition to be an important source of PCBs to Lake Michigan Implicated air pollution and associated acid deposition in the disappearance of Sphagnum mosses from northern English bogs during the industrial age Showed toxicity to fish of aluminum released from soils by acid deposition Inferred pH profiles in dated cores of lake sediment from diatom stratigraphy Demonstrated that adverse effects of acid deposition on fish can occur via harm to food organisms Showed rapid recovery of catchments following reduced acid loading Demonstrated high concentrations of organochlorine contaminants in arctic marine fauna due to long-range transport and bioaccumulatic)
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From page 99... ...
Negative effects range from clogging of water intake pipes for industries and water treatment plants to loss of important native mussels and clams that cannot compete with the invader. For example, at a water treatment plant on Lake Erie, a combination of zebra mussels and ice completely blocked the intake, so that the city of Monroe, Michigan, had to impose emergency water conservation measures and close businesses and schools.
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From page 100... ...
Although it is not possible to eliminate zebra mussels from water bodies where they have become established, limnologists are studying a variety of physical, chemical, and biological control measures. These include the use of ultraviolet radiation to kill larval forms of zebra mussels, application of high-voltage fields on water intake pipes, use of various chemicals to kill adults or prevent larval attachment, and isolation of bacteria that inhibit larval attachment or cause disease in zebra mussels.
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From page 101... ...
that have been stocked in the lakes. Whereas the zebra mussel and Bythotrephes were introduced to the Great Lakes accidentally, introductions of nonnative species are often intentional.
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From page 102... ...
Rainbow smelt are currently spreading through inland lakes throughout the Midwest with as yet unknown but likely important consequences for native species and food webs (Evans and Loftus, 1987~. Important invasions of aquatic ecosystems have not been limited to animal species.
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From page 103... ...
An important lesson to be derived from exotic species invasions and introductions is that aquatic communities often are delicately balanced. Shifts caused by invading species can have substantial effects on ecosystem and community structure, as well as on fundamental ecosystem processes, and often these shifts have impacts that are not desirable.
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From page 104... ...
This information can be used to develop management practices that minimize both the occurrence of extirpation within particular habitats and, ultimately, overall species extinctions. Second, limnologists are working to develop an understanding of aquatic ecosystems sufficient to predict the effects of the loss of a species on the entire community and on ecosystem processes.
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From page 105... ...
CONTEMPORARY WATER MANAGEMENT 105 affect water quality and aquatic communities, how fossil fuel emissions lead to the degradation of aquatic systems, and what mechanisms lead to the deterioration of lakes and rivers via cultural eutrophication. Advances in knowledge achieved by limnologists and aquatic scientists in related fields have led to plans for long-term management of important aquatic ecosystems (see, for example, Box 3-11~.
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From page 106... ...
1986. Background pollution in the arctic air mass and its relevance to North American acid rain studies.
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From page 107... ...
1990. Effects of climatic warming on dissolved oxygen concentrations in Lake Erie.
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From page 108... ...
1984. Acidic deposition: Effects on aquatic ecosystems.
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From page 109... ...
1988. Primary productivity, nutrients, and transparency during the early onset of eutrophication in ultra-oligotrophic Lake Tahoe, California-Nevada.
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From page 110... ...
1993. Changes in planktonic diatoms and water transparency in Hatchery Bay, Bass Island area, western Lake Erie since the establishment of zebra mussel.
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From page 111... ...
1989. The metropolitan wastewater treatment plant and the Mississippi River: 50 years of improving water quality.
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From page 112... ...
1990. Potential changes in thermal structure and cycle of Lake Michigan due to global warming.
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From page 113... ...
1992. Restoration of Aquatic Ecosystems.
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1995. "Scientific uncertainty" scuttles new acid rain standard.
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From page 115... ...
In press, a. The effects of climatic warming on the properties of boreal lakes and streams at the Experimental Lakes Area, Northwestern Ontario.
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From page 116... ...
Occurrence and bioaccumulation of organochlorine compounds in fishes from Siskiwit Lake, Isle Royale, Lake Superior. Environ.
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From page 117... ...
1971. Water pollution in Lake Michigan by trace elements from pollution aerosol fallout.
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