Lake Michigan

Lake Michigan’s habitats support a diverse array of plant and animal species and its waters continue to provide opportunities for swimming and recreational use. However, invasive species and other stressors continue to affect both water quality and the lake’s food web.

  • A cup with water in it. The caption reads “Be a source of safe, high quality drinking water”. The lake icon is green, indicating a status of Good.

    Be a source of safe, high quality drinking water.

  • A person swimming at the surface of the water with their arm over their head. The caption reads “Allow for unrestricted swimming and other recreational use”. The lake icon is green, indicating a status of Good.

    Allow for unrestricted swimming and other recreational use

  • A fish mid-jump. The caption reads “Allow for unrestricted human consumption of the fish and wildlife”. The lake icon is yellow, indicating a status of Fair.

    Allow for unrestricted human consumption of the fish and wildlife

  • An industrial complex with smoke coming out of smokestacks. The caption reads “Be free from pollutants that could harm people, wildlife, or organisms”. The lake icon is yellow, indicating a status of Fair.

    Be free from pollutants that could harm people, wildlife, or organisms

  • A heron standing next to some trees. The caption reads “Support healthy and productive habitats to sustain our native species”. The lake icon is yellow, indicating a status of Fair.

    Support healthy and productive habitats to sustain our native species

  • Two microorganisms next to each other. The caption reads “Be free from nutrients that promote unsightly or toxic blooms”. The lake icon is yellow, indicating a status of Fair.

    Be free from nutrients that promote unsightly or toxic blooms

  • An invasive Carp and two dreissenid mussels with invasive Phragmites in the background. The caption reads “Be free from aquatic and terrestrial invasive species”. The lake icon is red on the left and green on the right, indicating a status of Poor to Good.

    Be free from aquatic and terrestrial invasive species

  • A pump with water dripping into cup. The caption reads “Be free from the harmful impacts of contaminated groundwater”. The lake icon is grey, indicating a status of No Trend.

    Be free from the harmful impacts of contaminated groundwater

  • A city skyline with a lake and waves in the foreground and rain and clouds in the sky. The caption reads “Be free from other substances, materials, or conditions that may negatively affect the Great Lakes”. The lake icon is yellow on the left and green on the right, indicating a status of Fair to Good.

    Be free from other substances, materials or conditions that may negatively affect the Great Lakes

Status legend: Good (green), fair (yellow), poor (red)

Lake Michigan continues to be a good source for producing high-quality drinking water and provides good opportunities for swimming and recreation. Concentrations of many toxic chemicals continue to decline in monitored media; however, fish consumption advisories due to contaminant levels in fish fillets that exceed benchmarks continue to be issued. Lake Michigan has both healthy wetlands with some of the highest amphibian and bird species richness observed in the Great Lakes as well as wetlands with degraded plant and animal communities. Lake Michigan wetlands are generally in Fair condition. In some nearshore areas, there is excessive growth of the nuisance alga Cladophora, and toxic blooms of cyanobacteria regularly occur in Green Bay. Aquatic habitat connectivity is considered Poor with over 80% of tributary habitat no longer accessible to migratory fish; however, projects implemented over the past decade to remove barriers or improve fish passage have increased connectivity, resulting in more tributary habitat accessible to native fish like Lake Sturgeon.

Offshore, invasive filter-feeding Quagga Mussels have contributed to low phosphorus levels and reduced Phytoplankton biomass. Significant declines in Zooplankton biomass in the mid-2000s have now stabilized to levels half of what they were observed in 1997-2002; current observed biomass and community structure are consistent with expected levels for oligotrophic deep lakes and the species assemblage is in Good condition. Conversely, Diporeia populations are in Poor condition and continue to decline. Despite these challenges, increased natural reproduction of Lake Trout is evident, due in part to the successful control of invasive Sea Lamprey. Lake Trout is an important species that contributes to Lake Michigan’s $1.7 billion sport fishery. Populations of other important fish species in Lake Michigan, such as Walleye, remain in Good condition.

Groundwater quality, measured in terms of nitrate and chloride concentrations, is assessed as Undetermined due to limited data availability. Agricultural and urban development and increased shoreline hardening threaten water quality in Lake Michigan. Lake Michigan has experienced long-term increases in surface water temperature and decreases in winter ice cover.

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