The 2012 Great Lakes Water Quality Agreement states that “the Waters of the Great Lakes should support healthy and
productive wetlands and other habitats to sustain resilient populations of native species.”
Assessment highlights
The Habitat and Species indicator includes assessments of Great Lakes coastal wetlands, habitat connectivity, and species that are part of the aquatic food web. Coastal wetland and aquatic food web health are variable across the basin, ranging from Good to Poor and Improving to Deteriorating, depending on the lake, habitat, and species of interest. Overall, the Habitat and Species indicator is assessed as Fair and the 10-year trend is Unchanging.
Restoration and protection efforts have improved habitat conditions at many coastal wetlands. Wetlands are important to restore and protect as they provide ecological, economic and cultural benefits. Lake Superior wetlands and those along the northern shorelines of lakes Michigan and Huron are generally in better condition than wetlands in lakes Erie and Ontario. For example, most of the wetlands in lakes Erie and Ontario have degraded plant communities as a result of nutrient enrichment, sedimentation, invasive species, or combinations of these factors. These stressors can allow invasive plants such as Cattails, European Frog-bit, Phragmites (sometimes called Common Reed), and Water Chestnut to thrive, reducing biodiversity and habitat quality for native flora and fauna.
Amphibian, bird, and fish communities in coastal wetlands tend to be healthiest where the footprint of human activity is the lowest. Coastal wetland amphibian and bird community health in each of the lakes are considered Fair with no trend towards improvement or deterioration. Coastal Wetland Fish communities are assessed as Good in Lake Superior, Poor in Lake Erie and Fair in the other three lakes. Coastal wetland fish are in Poor condition in Lake Erie due in part, to the abundance of non-native fish in the lake, which compete with native fish for resources, and can degrade habitat. The Canada Water Agency has updated estimates of Canadian coastal wetland extent. Estimates range from approximately 17,000 hectares in Lake Ontario to over 27,500 hectares in Lake Erie. Work is underway to update basin-wide estimates of coastal wetland extent, inclusive of wetlands in the U.S. Great Lakes basin.
Aquatic habitat connectivity assesses the percentage of tributary lengths that remain free of dams or other barriers impacting the connection between the headwaters and the Great Lakes. The connectivity of tributaries is critical for migratory fish to reach spawning habitat and to maintain other ecological processes such as natural sediment transport. Tributary connectivity was reduced in each lake basin during the past century but is currently assessed as Fair and is Improving in the basin as a result of barrier removal and fish passage projects. These restoration efforts must also consider the potential risks of allowing nonnative species to access the Great Lakes, or creating spawning habitat for species like Sea Lamprey.
The Great Lakes aquatic food web contains many interacting species, from tiny algae (Phytoplankton) and animals (Zooplankton) to large fish. Changing nutrient conditions combined with the impacts of invasive species, especially Dreissenid Mussels (Zebra and Quagga mussels), are some of the most immediate stressors to the Great Lakes food web. Dreissenid Mussels filter phytoplankton from the water column and alter the way nutrients are cycled through the lakes, resulting in reduced food for Zooplankton, which impacts higher components of the aquatic food web, including fish.
Across the Great Lakes, Phytoplankton trends are variable while Zooplankton trends are largely Unchanging. Lake Superior has maintained Phytoplankton and Zooplankton communities reflecting oligotrophic (low nutrient) conditions and is assessed as Good for Phytoplankton and Zooplankton, but gradual community shifts toward Phytoplankton groups that thrive in warmer conditions may be occurring in response to increasing surface water temperatures, resulting in a Deteriorating trend. In lakes Huron and Michigan, declines in spring Phytoplankton biovolume resulted in decreased Zooplankton biomass in past decades, but Phytoplankton biovolumes have generally stabilized in recent years. Phytoplankton is assessed as Fair in lakes Huron and Michigan, while Zooplankton is assessed as Good in Lake Michigan and Fair in Lake Huron. In Lake Erie, Phytoplankton is assessed as Poor and Deteriorating due to increases in the abundance of cyanobacteria, but Zooplankton communities are in Good condition due to high lake productivity.
Diporeia, a small benthic (bottom-dwelling) invertebrate and an important food source for fish, severely declined in the 1990s and are in Poor status in all lakes except Lake Superior. The mechanisms causing these declines are complex and are still being studied to better understand the full impacts. Dreissenid Mussels have likely contributed to these trends by altering benthic habitat and reducing the amount of available food for other benthic organisms, including Diporeia. In Lake Superior, Diporeia remain the dominant benthic organism, resulting in a Good status. The decline in Diporeia in the Great Lakes has likely increased the importance of Mysis, another lipid-rich prey, in the food web. Current Mysis densities in all lakes, except Lake Michigan, are assessed as Good. Conditions in Lake Michigan are Poor and Deteriorating due to declines in Mysis density and primary productivity.
Phytoplankton, Zooplankton, and benthic communities are important sources of food for prey fish and young sport fish and are essential to sustaining a healthy food web. The diversity of prey fish communities across the Great Lakes continues to change, although the direction and magnitude of those changes vary. The prey fish community is considered Fair overall based on the diversity and the proportion of native prey fish species in the Great Lakes. There have been fluctuations in the overall abundances of prey fish, which are influenced by both food availability and the number of top predator fish such as Lake Trout, Salmon, and Walleye. A balance between the number of predator fish and the available prey fish in the lakes is important for a sustainable Great Lakes Fishery.
Sustainable fishery management, ongoing Sea Lamprey control, improving water quality, population rehabilitation stocking, and restoration of spawning habitat have contributed to Improving Lake Sturgeon, Walleye and Lake Trout populations, including increased reproductive success for Lake Trout. Populations of Lake Trout have also improved due to declines in Alewives, an invasive prey fish that causes thiamine deficiency in Lake Trout. In the mid-1900s, Lake Trout populations declined to extremely low levels in Lake Superior due to extensive overfishing and the impacts from the invasive, predatory Sea Lamprey. However, the Great Lakes Fishery Commission announced in the fall of 2024 that Lake Trout populations are considered fully recovered in most of Lake Superior. There is also evidence of increased natural reproduction of Lake Sturgeon in tributaries throughout the Great Lakes basin, due in part to habitat improvements, dam removals, and stocking efforts. However, changes in Lake Sturgeon status will take a long time to manifest due to the long lifespan of the species. A key highlight for Walleye in Lake Huron is that the population has increased substantially, resulting in an Improving trend.
Coastal wetland birds are in Fair condition overall in the Great Lakes
Mysis population density is in Good condition in lakes Huron, Ontario and Superior
Green dashed lines represent lake-specific thresholds for Good Mysid densities. Mysis in Lake Erie are limited to the deep portions of the eastern basin. Available data are insufficient for trend analysis and are not included in this figure.
Sub-indicators supporting the Habitat and Species assessment – Coastal Wetlands and Aquatic Habitat Connectivity
Sub-Indicator | Lake Superior | Lake Michigan | Lake Huron | Lake Erie | Lake Ontario |
Coastal Wetland Invertebrates | Fair & No Trend | Fair & No Trend | Fair & No Trend | Undetermined & Undetermined | Undetermined & Undetermined |
Coastal Wetland Fish | Good & Improving | Fair & No Trend | Fair & No Trend | Poor & No Trend | Fair & No Trend |
Coastal Wetland Amphibians | Fair & No Trend | Fair & No Trend | Fair & Deteriorating | Fair & No Trend | Fair & No Trend |
Coastal Wetland Birds | Fair & No Trend | Fair & No Trend | Fair & No Trend | Fair & No Trend | Fair & Unchanging |
Coastal Wetland Plants | Good & Unchanging | Fair & Unchanging | Good & Unchanging | Poor & Unchanging | Poor & Unchanging |
Coastal Wetland Extent & Composition | Not Assessed | Not Assessed | Not Assessed | Not Assessed | Not Assessed |
Aquatic Habitat Connectivity | Fair & Improving | Poor & Improving | Fair & Improving | Fair & Improving | Fair & Improving |
Sub-indicators supporting the Habitat and Species assessment – Aquatic Food Web
Sub-Indicator | Lake Superior | Lake Michigan | Lake Huron | Lake Erie | Lake Ontario |
Phytoplankton | Good & Deteriorating | Fair & Unchanging | Fair & Unchanging | Poor & Deteriorating | Good & Unchanging |
Zooplankton | Good & Unchanging | Good & No Trend | Fair & Unchanging | Good & No Trend | Fair & No Trend |
Benthos | Good & Unchanging | Good & Unchanging | Good & Unchanging | Poor & Unchanging | Fair & Unchanging |
Diporeia | Good & Unchanging | Poor & Deteriorating | Poor & Deteriorating | Poor & Unchanging | Poor & Unchanging |
Mysis | Good & Unchanging | Poor & Deteriorating | Good & Unchanging | Good & Undetermined | Good & Unchanging |
Lake Sturgeon | Poor & Improving | Poor & Improving | Poor & Improving | Poor & Improving | Poor & Improving |
Native Prey Fish Diversity | Fair & Unchanging | Fair & Unchanging | Fair & Unchanging | Poor & Unchanging | Poor & Unchanging |
Lake Trout | Good & Improving | Fair & Improving | Fair & Unchanging | Fair & Improving | Fair & Improving |
Walleye | Fair & Improving | Good & Unchanging | Fair & Improving | Good & Improving | Good & Unchanging |
Fish-Eating & Colonial Nesting Waterbirds | Poor & Deteriorating | Not Assessed | Poor & Deteriorating | Fair & Unchanging | Fair & Deteriorating |
Status
