Lake by lake
Resources and references
About the Great Lakes LaMPs study...
Glossary of terms
Lake Erie is the smallest of the Great Lakes in volume (116 cubic miles) and is exposed to the greatest effects from urbanization and agriculture. Measuring 241 miles across and 57 miles from north to south, the lake's surface is just under 10,000 square miles, with 871 miles of shoreline. The average depth of Lake Erie is only about 62 feet (210 feet, maximum). It therefore warms rapidly in the spring and summer, and frequently freezes over in winter. The drainage basin covers parts of Indiana, Michigan, Ohio, Pennsylvania, New York, and Ontario. Because of its fertile soils, the basin is intensively farmed and is the most densely populated of the five lake basins.
In most communities, drinking water is treated to remove contaminants before being piped to consumers, and bacterial contamination of municipal water supplies has been largely eliminated by adding chlorine or other disinfectants to drinking water to prevent waterborne disease. By treating drinking water and wastewater, diseases such as typhoid and cholera have been virtually eliminated. Although other disinfectants are available, chlorination still tends to be the treatment of choice. When used with multiple barrier systems (for example, coagulation, flocculation, sedimentation, and/or filtration), chlorine is effective against virtually all infective agents.
Over time, public water systems have been found to supply drinking water of good quality. Monitoring and corrective measures to reduce and eliminate levels of contaminants in treated water are essential components in continuing to assure the safety of drinking water supplies. As the population grows and more people rely on the drinking water supply from the lakes, these control measures must be adequate to reduce the risk from exposure to microbes. Ultimately, however, source water protection (protection of the raw waters) is the key to maintaining the good quality of drinking water supplies. The Lake Erie LaMP has designated the drinking water use of Lake Erie as unimpaired.
Contaminants are clearly bioaccumulating in Lake Erie biota on a continuum from benthos to fish to amphibians and reptiles, birds, and mammals. In addition, the filter feeding habits of the non-indigenous invasive zebra mussel are re-introducing contaminants not previously biologically available back into the water column and ultimately into the food web.
Benthic organisms spend most or all of their lifecycle in the sediment of the lake. Some fish are benthic feeders or spend most of the time near the bottom; others eat organisms that have spent part of their lifecycle as benthos. Finally, birds and mammals prey on these same fish. Each organism has bioaccumulated contaminants during its lifecycle, and the effect magnifies as one moves up the food chain (biomagnification). There are species used as indicators of this phenomenon (midges, mayflies, brown bullhead, bald eagle and herring gull) for which we have the most information. However, the list of species used to monitor contaminant impacts has grown in recognition of widespread bioaccumulation.
The critical pollutants and chemical pollutants of concern in Lake Erie include organochlorines and metals that are known to cause adverse health effects in animals and humans. These chemicals do not break down easily, persist in the environment, and bioaccumulate in aquatic biota, animal and human tissue; thus they are called persistent bioaccumulative toxic chemicals (PBTs). Organochlorines tend to accumulate in fat (such as adipose tissue and breast milk), and metals tend to accumulate in organs, muscle and flesh. Food is the primary route of human exposure to these PBT chemicals, and consumption of Great Lakes fish is the most important source of exposure originating directly from the lakes. Sources from air, soil/dust, and water constitute a minor route of exposure.
Since the 1970s, there have been steady declines in many PBT chemicals in the Great Lakes basin, leading to declines in levels in human tissue, for example, lead in blood and organochlorine contaminants in breast milk. However, PBT chemicals, because of their ability to bioaccumulate and persist in the environment, continue to be a significant concern in the Lake Erie basin. Although contaminant levels in the Great Lakes are declining in general, recent trends suggest that concentrations for some pollutants may be leveling off. However, health concerns from environmental contaminant exposures in the Lake Erie basin remain. Therefore, public health advisories and other guidelines should be followed to minimize contaminant exposures. Most of the health effects studies for Great Lakes PBT chemicals have focused on fish consumption.
Many sources contribute to microbiological contamination, including combined or sanitary sewer overflows (CSOs and SSOs), unsewered residential and commercial areas, and failing private, household and commercial septic systems. However, it is important to note that simply because bacterial levels are present, it does not necessarily mean that sewage overflow is a problem. Other sources may be agricultural runoff (such as manure); fecal coliforms from animal/pet fecal waste washed from soil by heavy rains, either from the beach or washed into residential storm sewers; wildlife waste, as from large populations of gulls or geese fouling the beach; direct human contact, such as swimmers with illnesses, cuts or sores; or high numbers of swimmers and bathers in the water, which are related to increased bacterial levels; and direct discharges, for example from holding tanks of recreational vessels.
Other factors affecting contamination levels are low (shallow) water levels; hot weather and higher temperatures; high winds that can cause increased wave action that can transport bacteria from contaminated, non-recreational areas to recreational-use areas; high winds that can stir up bacteria that are in the sediments; and calmer waters that can slow dispersal and create excess concentrations of bacteria.
Recreational water quality impairment includes situations where partial body contact recreation standards are exceeded. To be complete, an assessment needs to evaluate all recreational water use activities where total or partial body water contact may occur. This includes primary activities such as swimming, windsurfing and water skiing, and also situations where swimming may occur in open waters during secondary contact activities, such as boating and fishing.
Federal, state and provincial recreational water quality guidelines recommend bacterial levels below which the risk of human illness is considered to be minimal. When contaminant indicator levels in the bathing beach water reach levels that indicate contaminants may pose a risk to health, public beaches are posted with a sign warning bathers of the potential health risk.
Last modified: May 20, 2005