Why is Lake Michigan So Clear?

Lake Michigan, one of the five Great Lakes, has seen a remarkable improvement in its water clarity in recent years. This phenomenon is not only surprising but also significant for both ecological and human perspectives. The clarity is attributed to several factors, including the presence of invasive species, reduced industrial pollution, and the absence of sewage discharge. This article explores these key reasons and their implications.

Role of Sandy Soils and Environmental Laws

One of the primary contributors to the clarity of Lake Michigan is its surrounding sandy soils, which are remnants of glacial activity. Sandy soils play a crucial role in filtering water as it seeps through the land, reducing sediment and pollutants before they reach the lake. Additionally, strict environmental laws have been implemented to prevent industrial pollution, further enhancing the lake's water quality.

Chicago's Role in Protecting Lake Michigan's Water

The largest factor in maintaining the clarity of Lake Michigan is the city of Chicago, which has been a key player in this preservation. Unlike other cities that dump sewage into the lake, Chicago has taken a different path. In the mid-1800s, the city reversed the course of the Chicago River, redirecting it away from Lake Michigan and connecting it to the Des Plaines River, eventually leading to the Mississippi River. This engineering feat, known as the Chicago Sanitary and Ship Canal, has prevented sewage and wastewater from entering the lake for over 150 years.

Invasive Species and Their Impact

Invasive species, such as zebra mussels, have significantly contributed to the lake's clarity. Zebra mussels are filter feeders that can drastically reduce algal levels, leading to clearer water. A study published in Invasive Mussels journal titled Invasive Zebra Mussels Improve Water Clarity in the Great Lakes found that these mussels have substantially increased water clarity in Lake Michigan and other Great Lakes.

However, the introduction of these invasive species also has unintended consequences. As they filter out particles that are essential for the growth of native species, the new clarity is not without drawbacks. This reduction in nutrients can negatively impact the ecosystem, leading to a loss of biodiversity and ecological balance.

Reduction in Algal Growth

Another significant factor in the clarity of Lake Michigan is the reduction in algal growth. This has been achieved through effective measures to reduce phosphorous inputs, which are commonly used in fertilizers and other agricultural practices. A study published in Journal of Great Lakes Research, titled Revisiting the Great Lakes Water Quality Agreement: Phosphorus Targets and Predicting the Trophic Status of Lake Michigan, highlights the importance of reducing phosphorous levels to maintain water quality. By controlling phosphorous inputs, algal growth has been reduced, leading to clearer water.

The Ice Cover and Its Effect

One of the most recent and significant factors contributing to the clarity of Lake Michigan is the extended ice cover that has kept the lake surface protected from external inputs. For months, the lake was covered by ice, which prevented the entry of suspended sediments from rivers and streams, as well as reduced algal growth. The absence of these inputs has maintained the high clarity of the water.

However, as the ice melts and the spring phytoplankton bloom begins, the water clarity may decrease. This cycle has been observed over the past few decades and is a natural part of the ecosystem. As the lake warms and the phytoplankton bloom increases, the clarity of the water is likely to decrease, highlighting the importance of understanding and managing these natural cycles.

Conclusion

The increased clarity of Lake Michigan is the result of a combination of factors, including the presence of invasive species, reduced industrial pollution, and the absence of sewage discharge. However, it is important to recognize that this clarity is not without its challenges. The reduction in algal growth and nutrient inputs has positive effects on water quality, but it can also lead to ecological imbalances. Understanding these factors and managing the lake's ecosystem effectively will be crucial for maintaining the clarity and health of Lake Michigan.

Keywords: Lake Michigan, Water Clarity, Invasive Species