Ecological health effects of mercury
Most of the attention around mercury focuses on lakes and other aquatic ecosystems
(rivers, streams, wetlands and oceans). This is due to the fact that the levels of mercury
usually found in terrestrial environments are not high enough to represent a threat to the
health of wildlife or humans. However, humid environments such as wetlands and lakes
favor the transformation of mercury into its most poisonous form, methylmercury which
exhibit toxic effects at much lower concentrations. The presence of methylating bacteria
and living organisms, that will initially absorb methylmercury in their food diet, then
creates proper conditions for the bioaccumulation of methylmercury in fish communities.
Many species of fish and wildlife, which rely on fish for food, become at risk of mercury
poisoning. Otters, loons, minks and osprey are all examples fish-eating species in
Canada that might be in danger.
Loons have been studied extensively so that scientists can learn more about the effects of
mercury on species with a high fish diet, as well as to determine whether mercury is
harming loons. Many loons in eastern Canada and the northeastern United States have
high mercury levels that are causing serious reproductive and behavioral problems.
The presence of mercury in hydro reservoirs has been a serious issue in northern Canada,
and particularly in Quebec, where some of the world’s largest hydro reservoirs are
located. Large hydro reservoirs that flood hundreds or thousands of square kilometers of
forest become the perfect habitat for mercury methylation to occur. The decomposing
forest creates an ideal environment for microorganisms to convert the natural mercury in
soils, together with the mercury deposited by human activities, into methylmercury. The
methylmercury accumulates in aquatic species, making certain fish unsafe to eat for
wildlife and humans for several decades after impoundment.