Lake Erie’s Dead Zones Have Multiple Causes

Lake Erie

Lake Erie is the smallest of the Great Lakes and it suffers from what are called “dead zones,” or areas of depleted oxygen levels. Without oxygen in the water, aquatic life like fish cannot survive in these dead zones, which poses a problem for the Great Lakes’ largest producer of fish. As scientists research these dead zones, multiple causes are being pointed out as the perpetrators and will have to affect how decision makers treat Lake Erie in the future.

Drought and fertilizer runoff are two common causes of Lake Erie’s infamous dead zones. Without the replenishing waters from streams and rivers, the water in the lake is at a low level, which reduces the amount of oxygen available for the fish who live there. Intense storms, on the other hand, increase the water level, but can also wash in fertilizer from the surrounding area, which can affect the growth of algae in the lake. Algae blooms are toxic and contribute to the lake’s dead zones.

Both of these causes increase the amount of phosphorous in Lake Erie and reducing phosphorous levels has been a primary focus of policy makers. But a new study released this week encourages decision makers to factor in weather to their future conservation plans. While human causes of the dead zones are important, the influence of weather on Lake Erie is the greater factor. The report by the Carnegie Institution for Science looked at the biggest recorded dead zone for the lake in the summer of 2012 and their conclusion was weather was the deciding factor.

Co-author Anna Michalak emphasized how the water comes in to the lake as the biggest influence. ” That can lead to very different but quite negative impacts on the water quality in Lake Erie,” she said in an interview. Historical research into weather patterns over time revealed four triggers for some of the bigger dead zones that appear in Lake Erie. Low water levels due to reduced inflow from the rivers, influx of phosphorous levels, northwesterly winds that affect the flow of nutrients from one side of the lake to the other and wind speeds over the lake all played a role in creating large dead zones.

According to Michalak, the conclusion the researchers came to was that weather factors can really affect the creation of dead zones. But that does not mean that the human impact on the Lake Erie environment can be discounted. According to Michalak, the results “show how what we do as human beings really causes different impacts depending on meteorology conditions.” This is an important conclusion for policy makers concerned with preserving the lake. While some things are certainly within human control, other factors are not and they have to play a role in any decision made regarding Lake Erie.

Lake Erie is the smallest of the Great Lakes in term of water depth, but it produces more eatable fish than the other lakes. Walleye and perch are popular eating choices and their numbers are affected by the dead zones. Research into the dead zones like that of the Carnegie Institution for Science can lead to better decisions on how to treat the lake and preserve it. The fact that Lake Erie’s dead zones have multiple causes that must be considered in the decision making process can lead to better decisions and an improved environment for the lake.

By Lydia Bradbury

Sources:

Photo by Ryan Hodnett – Flickr License

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