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Freshwater Ecosystems: Revitalizing Educational Programs in Limnology
because they accumulate the highest levels of mercury. Figure 3-4 provides an example of advisory recommendations for an individual lake in northern Minnesota contaminated by atmospheric deposition of mercury.
Wildlife, of course, cannot respond to fish advisories, nor do all humans heed the warnings. Birds such as belted kingfishers, common loons, ospreys, and bald eagles consume large amounts of fish, as do mink and river otters among the mammals. In Minnesota there is evidence that mercury accumulation may be impairing reproduction by common loons. There is also an indication that walleye reproduction may be affected. Elevated concentrations of mercury have been detected in some mink and river otters. Researchers attributed the death of a Florida panther—a rare and endangered species—in the Everglades in 1989 to elevated levels of mercury found in the animal's liver, leading to concern about mercury pollution throughout the south Florida ecosystem (Jordan, 1990). In the Great Lakes and below pulp mills, organochlorine compounds delivered via the air and other routes have been linked with reproductive
FIGURE 3-4 Minnesota fish consumption advisory, 1994. "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.