Lake Michigan ecosystem

• Category: Inland Aquatic Biomes.
• Geographic Location: North America.
• Summary: The third-largest of the Great Lakes, Lake Michigan is abundant with aquatic life and shipping history, but is damaged from pollution, overfishing, and invasive species.

Lake Michigan is the only one of the five Great Lakes to lie entirely within the borders of the United States. Surrounded by rocky shores, sandy dunes, and beaches in Wisconsin and Illinois to the west, Indiana to the south, and Michigan to the east and north, Lake Michigan is the third largest of the Great Lakes. It is contiguous with Lake Huron via the Straits of Mackinac; it also has been connected to the Atlantic Ocean and the Mississippi River via canals. Once abundant with diverse aquatic life, Lake Michigan has been subjected to problems of overfishing, industrial and agricultural pollution, and invasive species.

Lake Michigan is the fifth-largest lake in the world and third largest of the Great Lakes by surface area at 22,400 square miles (58,000 square kilometers)—and the second largest of the Great Lakes in volume, at 1,180 cubic miles (4,918 cubic kilometers). It is 307 miles (494 kilometers) long and averages 75 miles (120 kilometers) across; it has a 1,640-mile (2,640-kilometer) shoreline. The lake’s average and maximum depths are 279 feet (85 meters) and 923 feet (281 meters), respectively. Lake Michigan’s mean surface level is 577 feet (176 meters) above sea level, the same as Lake Huron. Lake water levels are highest in autumn and lowest in winter. Highest and lowest recorded levels occurred in summer 1986 and winter 1964, respectively.

Hydrologically, Lakes Michigan and Huron are the same body of water (sometimes called Lake Michigan-Huron), but are geographically distinct. Counted together, it is the largest body of fresh water in the world by surface area. The Mackinac Bridge is generally considered the dividing line between them. Both lakes are part of the Great Lakes Waterway connecting the westernmost port of Duluth, on Lake Superior, to the Atlantic Ocean via the St. Lawrence Seaway and canal system.

Geology and Formation

The Great Lakes formed when the glaciers of the Laurentian, or Wisconsin, glaciation retreated north 12,000 to 7,000 years ago. Along with carving out the lake basins, the glaciers depressed the land with their tremendous weight. Meltwater initially filled Lake Michigan, which was originally much larger.

Along the shores of northwestern Michigan and the southern Upper Peninsula of Michigan, one can find unique Petoskey stones. These stones are fossilized coral from a reef that grew during the Devonian Period, around 350 million years ago. When wet or polished, they show the surface pattern of six-sided corals. They were moved and deposited during the last glaciation.

During the Silurian Period, over 400 million years ago, Wisconsin was located near the equator and the land was submerged under a massive inland sea. Over time, the sea disappeared but left behind some of the most extensive reefs in the world today. Several of those reefs are in evidence in Wisconsin today, and one runs through Lake Michigan, dividing the lake into a northern and a southern section. This reef occupies the lake bottom between Milwaukee and Racine on the Wisconsin side, and Grand Haven and Muskegon on the Michigan side. Because of winds, river water, and the coriolis effect, water both north and south of the reef flows in a clockwise direction, bringing moderating warmer surface water to Michigan, which experiences summer temperatures 5 to 10°F (2 to 5°C) higher than the Wisconsin side.

The beaches of the western coast of the lake and the northernmost part of the east coast are rocky, while the southern and eastern beaches are sandy and dune-covered. This is partly because of the prevailing winds from the west, which also cause thick layers of ice to build on the eastern shore in winter.

Along the southern and southeastern shorelines lies the largest freshwater dune system in the world. Large sand dunes rise hundreds of feet above the surface of the lake; the largest, Sleeping Bear Dune, is more than 400 feet (122 meters) high. These dunes are comprised of soft, off-white quartzite sand, sometimes called “singing sands” for the squeaky noise made when one walks through it. The dunes there and at other points around the lake can be visited at a variety of state and national parks.

Aquatic Life

Lake Michigan is home to a variety of species of fish and other organisms. The food web is based on the primary producers, the phytoplankton, mainly green algae, blue-green algae, diatoms, and flagellates. These are consumed by a variety of filter-feeding animals, including zooplankton, shrimp, mollusks, and clams. These in turn are consumed by the smaller foraging fish, such as sculpin (various species) and perch (Perca flavescens), which are consumed by the predatory walleye (Sander vitreus), trout (Salvelinus namaycush), bass (Micropterus species), and salmon (Onchorynchus species).

Approximately 150 species of fish were once native to Lake Michigan and its watershed. However, that number declined and in the early 2020s, only 68 species of fish could be found in Lake Michigan. At least eight native species have become extinct from the lake.

Native American populations thrived on Lake Michigan fish communities, but when European settlers imported industrial fishing techniques, populations declined. Fishing catches peaked in the late 1880s, with massive amounts of lake trout and whitefish caught. The most dramatic example of this is the lake whitefish (Coregonus clupeaformis), of which nearly 6,000 pounds (2,722 kilograms) were caught in 1947. By 1956, less than 60 pounds (27 kilograms) were caught.

Fisheries

Historically important commercial fish species include lake trout (Salvelinus namaycush), lake whitefish (Coregonus clupeaformis), walleye (Sander vitreus), white sucker (Catostomus commersonii), yellow perch (Perca flavescens ), lake herring (Coregonus artedi), coho salmon (Oncorhynchus kisutch), chubs, and alewife (Alosa pseudoharengus).

One of the most productive fish to be caught in Lake Michigan was the lake trout. The commercial catch in 1878 was about 2,659 pounds (1,206 kilograms); it peaked in 1896 at just over 9,000 pounds (4,082 kilograms), and plummeted to 54 pounds (24 kilograms) in 1950. In addition to overfishing, predation by the invasive sea lamprey contributed to the decline. In 1962, the fishery for lake trout was closed in Wisconsin, Illinois, and Indiana. Catches began increasing again in the late 1970s when sea lamprey control began; the most productive year in recent history was 1999 with just over 900 pounds (408 kilograms).

Lake whitefish catches were also highest in the early days of the fishery, with over 12,000 pounds (5,443 kilograms) caught in 1879. Whitefish catches reached their nadir in 1920, fluctuating after this but never regaining the historic levels. The Wisconsin Department of Natural Resources stocks about 13 million salmon and trout in Lake Michigan each year, for both the commercial and recreational fisheries.

Human Factor

Lake Michigan water quality has diminished due to multiple contaminants, including human waste water and industrial discharge. Some of the most serious pollutants include mercury, polychlorinated biphenyls (PCBs), microplastics, and the chemicals and bacteria in human waste. In 1993, an outbreak of the bacterium Cryptosporidium sickened over 400,000 people via the Milwaukee drinking water system, among the largest public drinking water contaminations in US history. Furthermore, Green Bay, along the northwestern shore of the lake, contains one of the highest concentrations of paper mills in the world; these are a major source of PCBs and other pollutants. At the southern end of the lake, near Chicago, steel mills contribute to water pollution; in a particularly controversial case, the US Steel plant in Portage, Illinois, spilled the toxic compound hexavalent chromium into a tributary of the lake on two occasions in 2017.

The climate of the northern part of the lake is colder; the coastlines are generally less developed. It is sparsely populated except for the Fox River Valley, which drains into Green Bay. The more temperate southern basin of Lake Michigan is among the most urbanized areas in the Great Lakes system and contains the Milwaukee and Chicago metropolitan areas. This region is home to about 8 million people.

Lake Michigan is connected to other waterways by way of several canal systems. The Saint Lawrence Seaway and Great Lakes Waterway opened Lake Michigan to ocean-going vessels. The Great Lakes are also connected by canal to the Gulf of Mexico by way of the Illinois River (via Chicago ) and then the Mississippi River.

Lake Michigan has already been affected by global warming and climate change, and experts predict this will only worsen in the future. Beginning in 2017, the lake received frigid blasts attributed to climate change. This caused the lake's ice cover to thicken, which helped lower water temperatures and slowed evaporation. However, by 2020, the melting ice caused flooding. Beaches disappeared and roadways were covered with water. According to a report by the Environmental Law and Policy Center (ELPC), more flooding in nearby communities is expected in the future as global warming causes water levels to rise. This is particularly worrisome because many industries near the lake use toxic materials. These industries were built when water levels were much lower and are likely to become flooded. Additionally, more severe storms have impacted the lake and surrounding areas and higher winds, damaging rain, and storm surging have contributed to erosion. In 2022, over two hundred communities on the region's shoreline spent $878 million on repairs, according to the ELPC.

Historical Notes

The name “Michigan” is derived from the Native American Ojibwa name, Michi-gama, which means “great water.” The French explorer Samuel de Champlain called it the Grand Lac. It was later named Lake of the Stinking Water and also Lake of the Puans, after the Winnebago native people who occupied its shores. In 1679, the lake became known as Lac des Illinois because it gave access to the country of the Native Americans bearing that name. Three years before, the missionary Allouez called it Lac St. Joseph, by which it was often designated by early writers; others called it Lac Dauphin. Through the further explorations of Jolliet and Marquette, the lake received its current name of Michigan.

Before 800 CE, Lake Michigan’s shores were inhabited by the so-called Hopewell Indians. After their decline, the region was home for several hundred years to the Late Woodland Indians. The area is still inhabited by their descendants, including the Chippewa, Menominee, Sauk, Fox, Winnebago, Miami, Ottawa, and Potawatomi.

The first person to reach the deep bottom of Lake Michigan was J. Val Klump, a scientist at the University of Wisconsin–Milwaukee. Klump reached the bottom via submersible as part of a 1985 research expedition.

Bibliography

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