Lake Erie's Dead Zone Nothing New
The "dead zone" refers to the low oxygen conditions that develop near the bottom in most lakes when they have a cold lower layer and a warm upper layer in summer. Lake Erie's shallowness causes its lower layer to be so thin that the biota there may use up all the oxygen by the end of the summer. While the term "dead zone" conjures up images of a large die off of fish, the truth is that most animals, such as fish move elsewhere in the lake when the oxygen is low. Although this happens naturally in many lakes, early investigators were surprised it happened in Lake Erie - the term "dead zone" was coined by a newspaper to describe the low oxygen area in the middle of the central basin.
In the late 1960s and early 1970s, the "dead zone" was thought to be linked to nutrients that stimulate algae which then decompose to cause some of the oxygen consumption. For that reason, the elimination of low oxygen was a goal of the nutrient controls begun in the 1970s under the Great Lakes Water Quality Agreement with the U.S. Since then, Environment Canada's National Water Research Institute has been surveying the lake and conducting research almost every year. The research has shown that:
- Lake Erie is more prone to low oxygen because of its shallow depth.
- The severity of the low oxygen period depends heavily on weather factors in the spring and summer.
- Low oxygen conditions are expected even when algae levels are very low.
- Low lake levels tend to make the problem worse.
- Little or no change is expected due to zebra mussels in the lake.
- Low oxygen conditions still appear even though nutrient load reductions were achieved in the mid 1980s.
- Research and monitoring is continuing to determine the effects of increasing numbers of alien species introductions, nutrient loads, and climate change.
- Management of the oxygen situation is achieved through nutrient management which is done for purposes of surface water quality and fish habitat
Continuing research and monitoring will provide the necessary information to assess what actions, if any may be needed to address this situation. This will be determined through the Lake Erie Lakewide Management Plan process, a joint initiative of Canada and the United States, Ontario, and the states of Ohio, Michigan, Pennsylvania and New York.
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