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Surface Water: Rivers and Lakes - The Great Lakes

species pollutants fish ecosystem

The 2000 EPA Inventory of the Great Lakes

The Great Lakes basin, which is shared with Canada, is home to more than thirty-three million people, thirty million of whom rely on it for drinking water. The five lakes are the largest system of fresh surface water in the world, containing about 20% of the world's freshwater. The water in the Great Lakes accounts for 95% of all the freshwater in the United States. The total shoreline of the Great Lakes in the United States and Canada, a "fourth seacoast," is more than 10,000 miles long and equal to about one-quarter of the Earth's circumference. The region generates more than 50% of the total U.S. manufacturing output. The eight Great Lakes states (Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin) account for 30% of U.S. agricultural sales. International shipping on the Lakes annually transports fifty million tons of cargo while sport and commercial fishing contribute $4.5 billion to the economy.

This prosperity has taxed the ecological health of the Great Lakes system. Urban and industrial discharges, agricultural and forestry activity, development of recreation facilities, poor waste disposal practices, invasive species, and habitat degradation have all contributed to ecosystem decline. Despite these problems, however, the watershed still contains many ecologically rich areas. More than thirty of the basin's biological communities, and more than one hundred species, are found only in the Great Lakes basin or are globally rare.

In 2000 the states assessed 92% of the Great Lakes shoreline. The states reported that 22% of the assessed shoreline supported designated uses and 78% was impaired. Only four of the eight Great Lakes states reported specific pollutants and sources of those pollutants for use in the EPA's 2000 report. As the report states, "limited conclusions can be drawn from this fraction of the nation's Great Lakes shoreline miles."

The data presented in Figure 3.8 show the percentage of Great Lakes shoreline miles that either fully support or only partially support (or fail to support) each of six use categories. In all but one case, the percentage of assessed miles that support their use category well exceed the percentage that only partially support or fail to support a use category. The one use category in which partial failure to support or total failure to support was reported for all shoreline miles was fish consumption. Not being able to eat Great Lakes fish was the greatest use impairment. All of the states bordering the Great Lakes have issued advisories to restrict the eating of fish caught in the lakes.

Great Lakes Water Quality Agreement

Since the 1960s and 1970s, when Lake Erie was so degraded that it was considered by many to be "dead," much time and effort has been invested in trying to restore the Great Lakes system. In 1972 the United States and Canada entered into the Great Lakes Water Quality Agreement (GLWQA), which is a worldwide model for cooperative environmental protection and natural resource management.

There have been many successes since then, and the ecosystem is in recovery. For example, excess phosphorous and nitrogen loads that smothered the Great Lakes with nuisance algae have been successfully stabilized and in some cases reduced through strict nutrient goals. The trend in phosphorous concentration has been mostly downward and stable on all lakes other than Lake Erie, where readings from 2001 and 2002 show an upward spike. The endangered double-crested cormorant, a large fish-eating bird that was near extinction in the 1970s, is now more numerous on Lake Ontario than at any time in its previous recorded history.

State of the Lakes Ecosystem Conferences

The GLWQA imposes reporting requirements on both of its member countries and in an attempt to meet these FIGURE 3.8
Individual use support in the Great Lakes, 2000
SOURCE: "Figure 4-6. Individual Use Support in the Great Lakes," in 2000 National Water Quality Inventory, U.S. Environmental Protection Agency, August 2002
requirements a conference series was established. The conferences, which are held every two years, are called the State of the Lakes Ecosystem Conference (SOLEC). The first such conference was convened in 1994.

The SOLEC meetings are designed as a venue for scientists and policy makers to share information about the state of the Great Lakes ecosystem. The focus is on assessing and sharing information about the results of Great Lakes programs and studies. In the year following each conference, the United States and Canada prepare a report that presents the findings accumulated at the SOLEC.

According to the EPA's Web site (, after the 1996 SOLEC those involved recognized a need for a standard set of basin-wide indicators. When many parties are involved in studying a subject and then comparing the results of their studies, it is helpful to work with a standard set of indicators so that progress can be measured reliably across both time and geography.

Since the 1996 SOLEC, work has been done to establish a formalized set of indicators with which to assess the state of the Great Lakes at each consecutive SOLEC. The indicators are used sort of like a doctor might use a patient's weight and blood pressure to gauge his or her general health. Over time if an adult patient's weight and blood pressure are rising it is a sign of troubled health. Similarly, a rising phosphate level in a lake is a sign that the lake's ecosystem is ailing.

The report that came out after SOLEC 2002, State of the Great Lakes 2003, presented the following mixed news about the chemical, physical, and biological integrity of the waters of the Great Lakes Basin ecosystem:

Recreational waters have become contaminated with animal and human feces from sources such as combined sewer overflows that occur in certain areas after heavy rains, agricultural runoff, and poorly treated sewage.

Overall the quality of the drinking water in the Great Lakes basin is good. This is in large part due to our current technologies.

Since the 1970s, there have been declines in many persistent bioaccumulative toxic (PBT) chemicals in the Great Lakes basin. However, PBT chemicals, because of their ability to bioaccumulate and persist in the environment, continue to be a significant concern.

Wetlands continue to be lost and degraded, yet the ability to track and determine the extent and rate of this loss in a standardized way is not yet feasible.

These findings were based on the assessments of nineteen of the forty-five indicators reported on at the SOLEC 2002 meeting.

Pollutants and Sources of Pollution in the Great Lakes

The U.S. strategy for meeting the goals of the GLWQA is discussed in Great Lakes 2001—A Plan for the New Millennium. The draft strategy was a partnership among the eight Great Lakes states, Great Lakes tribal governments, the Great Lakes Fishery Commission, and nine federal agencies. These groups were working together to implement the actions described in the strategy by coordinating and enhancing their environmental protection and natural resource management efforts.

Priority toxic organic chemicals, nutrients, and pathogens are the three most common pollutants affecting the waters of the Great Lakes. Toxic substances such as mercury, heavy metals, dichlorodiphenyltrichloroethane (DDT), and polychlorinated biphenyls (PCBs) have been responsible for many of the problems. There has been some improvement, however. The levels of DDT, a banned pesticide, have steadily decreased since the mid-1970s, and there are currently no DDT-based advisories against eating fish from the Great Lakes. Total PCB levels have shown the same decline as DDT. PCB concentrations in lake trout, walleye, and salmon are one-tenth of the concentrations reported in the mid-1970s. The PCB levels, however, are still high enough to keep advisories against eating these fish from places in all five lakes. Contaminated sediments and urban runoff are the primary sources of the pollutants impairing the Great Lakes.


A mixing zone is an area in a river or lake where pollutants are mixed with cleaner waters to dilute pollutant concentrations in the water. Inside a mixing zone, discharges are allowed to exceed water-quality criteria by a fixed amount determined on a case-by-case basis. Outside the mixing zone, pollutant levels must meet water-quality standards.

Certain organic pollutants such as DDT, PCBs, and methyl mercury, even though their concentrations are so low that they cannot be measured in surrounding waters, bioaccumulate. The EPA has identified twenty-two bioaccumulative chemicals of concern. In November 2000 the EPA adopted a new regulation for the Great Lakes, prohibiting the use of mixing zones with new discharges of bioaccumulative chemicals. The rule also phased out over a ten-year period the use of existing Great Lakes mixing zones for these chemicals. The regulation was aimed at reducing, by up to 700,000 pounds, the annual discharge into the Great Lakes of chemicals that had the potential to accumulate in fish and wildlife. The EPA estimated that this new regulation would affect about 300 of the 600 major Great Lakes dischargers.


Some organic pollutants, including PCBs and DDT, have two properties that lead to high bioaccumulation rates. These pollutants do not have an affinity to water (they are hydrophobic) and therefore readily attach to particles such as clay and small aquatic plants called phytoplankton. The pollutants have an affinity for lipids or fatty tissues (they are lipophilic) and are therefore stored readily in the fatty tissues of plants and animals. Because of these properties, these organic pollutants bio-accumulate in phytoplankton, sediment, and fat tissue at concentrations that exceed the pollutant concentrations in surrounding waters. Frequently, the concentration in surrounding waters is so low that it cannot be measured even with very sensitive instruments and methods.

Zooplankton (microscopic plant-eaters) and fish consume vast quantities of phytoplankton. As a result, any organic chemicals accumulated by the phytoplankton are further concentrated in the fish, particularly in their fatty tissues. These concentrations are increased at each level FIGURE 3.9
Bioaccumulation of pollutants in the food chain
SOURCE: "Bioaccumulation of Pollutants in the Food Chain," in National Water Quality Inventory: 1998 Report to Congress, U.S. Environmental Protection Agency, 2000
of the food chain. (See Figure 3.9.) The process of increasing pollutant concentration through the food chain is called biomagnification.

The top predators in a food chain, such as lake trout and Chinook salmon, and fish-eating gulls, hawks, and eagles, may accumulate concentrations of these organic chemicals high enough to cause serious deformities or death, or impair their ability to reproduce. DDT, for example, causes the eggs of eagles, osprey, and other fish-eating birds to easily break, and also causes deformities in chicks, impairing the birds' ability to successfully reproduce.

Biomagnification of pollutants in the food chain can also be a significant concern for human health. To protect their residents from these risks, states issue fish consumption advisories or warnings about eating certain types of fish or shellfish.

The Threat of Alien Invasive Species

The introduction of a nonnative species into an ecosystem can have serious consequences. In fact, according to the State of the Great Lakes Ecosystem 2001, jointly published by the U.S. Environmental Protection Agency and Environment Canada, "invasive, non-native aquatic species are the greatest biological threat to the Great Lakes aquatic ecosystem."

Within an ecosystem there exists a balance. A new nonnative species brought into a system causes an imbalance and can cause great damage as native species are not capable of resisting infection, infestation, predation, or competition from the alien species. Two examples of such invasive nonnative species are the zebra mussel and purple loosestrife, an aquatic plant.

According to the International Joint Commission's 2002 report, researchers widely believe that the costs of biological pollution from alien invasive species are both massive and rising. The costs to native ecosystems, natural resources, fisheries, and agriculture are estimated in one study to reach $137 billion per year in the United States alone. By comparison, the costs associated with losses from Hurricane Andrew in 1992 totaled $16 billion.

Invasive alien species are introduced into the Great Lakes in various ways, including aquaculture, canals, baitfish disposal, recreational boating, and ship fouling. The most significant source of introduction of such species is through ballast water on ships, the water that ships take in at sea to equalize their loads. This ballast water, which may contain nonnative species, is often discharged in the Great Lakes.

Guidelines for ballast water were introduced as a part of the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 as amended by the National Invasive Species Act of 1996. Nonetheless, according to the International Joint Commission's 2002 report, "despite increased awareness of the risks, the 1990s saw no discernable improvement" in the introduction of nonnative species into the Great Lakes.

In its Twelfth Biennial Report on Great Lakes Water Quality, released in September 2004 (, the International Joint Commission estimated that the number of alien nonnative species had risen from approximately 162 in 2001 to more than 170 by late 2004. Scientists on the Commission predicted that one new invasive non-native species will be discovered in the Great Lakes every eight months. As of 2005, the International Maritime Organization Convention, which would enact a series of standards for ships entering the Great Lakes region to slow the number of nonnative species introduced to the area on the ballasts of ships, still had not been ratified. In the interim between its proposal and its eventual ratification, scientists estimate that as many as twelve new alien species could be introduced to the lakes and waterways of the region.

Surface Water: Rivers and Lakes - Do The Nation's Waters Meet The"fishable/swimmable" Goals? [next] [back] Surface Water: Rivers and Lakes - Water Quality Of The Nation's Lakes

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