Lake Erie, the southernmost of the Great Lakes, is the shallowest, with an average depth of only 62 feet. This allows its waters to warm quickly in the summer months. This warmer temperature profile, combined with nutrient inputs from the surrounding watershed, makes it the most biologically productive of all the Great Lakes, supporting a vast array of wildlife. For decades, the lake faced severe ecological decline due to industrial pollution and nutrient-fueled eutrophication. However, the lake has undergone a remarkable environmental recovery, yet it remains a dynamic ecosystem constantly shaped by environmental changes and the ongoing pressures of non-native species.
The Native Fish Communities
Fish are the most economically significant residents of Lake Erie, providing a world-class fishery. The lake’s productive waters support a diverse mix of cool-water and warm-water species across its three distinct basins. The Walleye (Sander vitreus) is the dominant species, thriving throughout the lake and supporting a massive recreational fishery. Walleye are cool-water fish that migrate between the lake’s basins, moving into deeper, cooler waters during summer and closer to shore in the spring and fall.
Another commercially and recreationally significant native species is the Yellow Perch (Perca flavescens), which schools near islands and in shallow bays. These smaller fish are a staple of the lake’s food web and are targeted by both commercial and charter operations. The Smallmouth Bass (Micropterus dolomieu) population also thrives, preferring the lake’s rocky shorelines and submerged reefs for habitat. Recovery efforts are underway for the massive Lake Sturgeon (Acipenser fulvescens), a large, primitive fish that can grow to over six feet in length.
Invertebrates and the Benthic Environment
The foundation of the Lake Erie ecosystem rests on its small, often unseen invertebrate life. Microscopic organisms like phytoplankton form the base of the food web, providing the initial energy source that sustains the larger community. Zooplankton, tiny animals that feed on the phytoplankton, are a critical link in the food chain, serving as a primary food source for many young fish. Changes in water temperature and the presence of invasive species have altered the seasonal timing and biomass of these zooplankton communities.
The native mayfly (Hexagenia) nymph is a historically important member of the benthic community, burrowing into the soft bottom sediments of the western basin. Its disappearance in the mid-20th century due to low oxygen levels was a clear sign of the lake’s declining health. Its return and current abundance is considered a strong indicator of improved water quality and ecological recovery. Other native macroinvertebrates, such as various species of crayfish, also contribute to the benthic environment, providing food for bottom-feeding fish and other predators.
Avian and Amphibious Residents
The Lake Erie shoreline and its islands serve as a biological bridge for a vast array of avian and amphibious life. The lake is positioned at the intersection of major North American migratory flyways, making its coastal areas and wetlands necessary stopover sites for millions of birds each spring and fall. Waterfowl, including various species of ducks and geese, along with shorebirds and gulls, utilize the open water and marshes for feeding and rest. The western basin is particularly renowned for hosting large numbers of migrating landbirds, such as warblers, as they cross the open water.
The coastal zones and islands also support a diverse community of reptiles and amphibians. Common Snapping Turtles (Chelydra serpentina) and Midland Painted Turtles are frequently found in the lake’s wetlands and along its edges. Several frog species, including the American Bullfrog and the Northern Leopard Frog, live along the marshy shorelines. Notably, the Lake Erie Watersnake (Nerodia sipedon insularum), a subspecies found only on the islands, has made a strong recovery thanks to conservation efforts.
The Influence of Invasive Species
The current Lake Erie ecosystem is fundamentally shaped by non-native species that have caused profound changes in the food web and water clarity. The most impactful invaders are the Zebra and Quagga mussels, which arrived via ballast water and filter enormous amounts of water, leading to a significant increase in water clarity. This filtering activity removes phytoplankton from the water column, shifting energy away from native zooplankton and into the benthic zone where the mussels live. The mussels also contribute to the formation of harmful algal blooms by selectively consuming non-toxic algae and leaving behind toxic cyanobacteria to flourish.
Another significant invader is the Round Goby (Neogobius melanostomus), a small, aggressive bottom-dwelling fish that has flourished by feeding extensively on the invasive mussels. The Goby competes with native benthic fish for food and preys voraciously on the eggs of native sport fish, including Smallmouth Bass. This species also acts as a pathway for contaminants like PCBs to move up the food chain, as native predators such as Walleye and Smallmouth Bass consume the Gobies.
The Sea Lamprey (Petromyzon marinus) also entered the lake via man-made canals. It is a parasitic species that attaches to and feeds on the blood and bodily fluids of large native fish. The lamprey’s attacks devastated populations of Lake Trout and other commercially valuable species in the early 20th century, though control efforts have since reduced its population by up to 95%.