Great Lakes: Resource at Risk
Fields, Scott, Environmental Health Perspectives
For centuries the Great Lakes have been treated callously. These five magnificent lakes--Superior, Michigan, Huron, Erie, and Ontario--located along the eastern half of the Canadian-U.S. border have served as a virtual sewer catching waste from industry, agriculture, commercial shipping, and households. Their natural barriers to other water systems have been breached, exposing indigenous ecosystems to aggressive invaders. They've been used as a highway for colossal ships that require deepened and broadened channels to crisscross the lakes, and that import exotic species along with their intended cargo. At times it could seem that this long-suffering water system will see no end of indignities. But recent renewed focus on the unique and tremendous value of this resource by governments and communities surrounding the lakes may turn the tide of neglect and abuse.
According to the U.S. Environmental Protection Agency (EPA), the Great Lakes contain 21% of the Earth's and about 84% of United States' surface freshwater. That's about 22,000 cubic kilometers of water spread over 94,250 square miles. Each year the lakes provide more than 6.7 million cubic meters of water to municipalities and quadruple that to industry. They support a commercial fishery worth about $13 million as of 2002, according to the U.S. Geological Survey (USGS), and a sport-fishing industry of nearly $1.3 billion as of 2001, according to the U.S. Fish and Wildlife Service. Today about 25% of Canadians and 10% of Americans--a total of more than 33 million people--live in the Great Lakes watershed.
"The whole industrial expansion that took place during the 'robber baron' era [of the late nineteenth century] expanded along the shores of the Great Lakes," says Deborah Swackhamer, a University of Minnesota professor of environmental chemistry. Soon ships were carrying iron ore, coal, and limestone from mines and quarries to steel mills and later steel to factories and products to markets. In addition to serving as a transportation system, the lakes provided a place to discharge
Unlike a sewer, however, whatever enters this lake system stays awhile. On average, less than 1% of the five lakes' water turns over each year, which means that many pollutants stay in place. They settle in sediments, adhere to other surfaces, become suspended in water, and bioaccumulate in organisms. Similarly, with the exception of migratory birds, most wildlife in the basin spend their entire life cycle in or near the lakes.
As a result of all these stressors, the lakes now house fish that are dangerous to eat, water that can be unsafe to drink, anoxic "dead zones"--areas in which virtually no plants or animals can survive--that appear each summer like clockwork, and an ever-growing population of unwanted species from other parts of the world.
The Great Catch-alls?
According to the EPA, 362 contaminants have been identified in the Great Lakes system, only about a third of which have been evaluated for their effects on wildlife and human health. Two decades ago the International Joint Commission (IJC)--an organization that was formed by the Boundary Waters Treaty of 1909 to prevent and mediate boundary water disputes between Canada and the United States--identified 11 of these as "critical pollutants" that required immediate attention. The list includes polychlorinated biphenyls (PCBs), DDT, dieldrin, toxaphene, mirex, mercury, benzo[a]pyrene, hexachlorobenzene, furans, dioxins, and alkylated lead.
All of these substances bioaccumulate in organisms and persist in the environment. Joseph Makarewicz, a professor of environmental science and biology at The State University of New York at Brockport, explains that many of these chemicals are attracted to fats and repelled by water. "They readily move into tissue," he says, "but basically it's through phytoplankton, zooplankton, forage fish . …