Lake Erie

• Category: Inland Aquatic Biomes.
• Geographic Location: North America.
• Summary: Among the North American Great Lakes, Lake Erie is the fourth-largest, the shallowest, and has the highest biodiversity—but it has suffered the most damage from agricultural runoff, industrialization, and urbanization.

Lake Erie was named after the indigenous Erie tribe that lived along its southern shore when French explorer Louis Jolliet discovered the area in 1669. By surface area, Lake Erie is the fourth-largest of the North American Great Lakes, and the smallest in terms of volume and average depth. It is the 11th-largest lake in the world by surface area. It forms an international boundary between the United States and Canada. Lake Erie is downstream from Lake Huron, and upstream from Lake Ontario.

The Canadian province of Ontario borders Lake Erie on the north; the states of Ohio, Pennsylvania, and New York line the southern shores; and Michigan adjoins the lake to the west. Lake Erie has a mean elevation of 569 feet (173 meters) above sea level. It has a surface area of 9,923 square miles (25,700 square kilometers), with a length of 241 miles (388 kilometers) and breadth of 57 miles (92 kilometers) at its widest point. Including its offshore islands, Lake Erie's total shoreline extends 871 miles (1,402 kilometers).

Geology and Depth

Like that of the other Great Lakes, Lake Erie's basin was carved from limestone and shale bedrock by glacial ice between 1.6 million and 10,000 years ago during periodic ice ages. Its shallow depth allows it to warm significantly in summer, and freeze over during cold winters. Lake Erie is rich in nutrients that enter its waters in runoff from the 34 inches (860 millimeters) of precipitation that annually falls upon its immediate region and flows through a watershed composed of highly fertile soils, agricultural fields, and large urban areas. Consequently, Lake Erie is the most productive of all the Great Lakes and boasts the highest biodiversity—but also suffers the most from pollution. Its relatively small size makes it more vulnerable than its sister lakes to these negative effects.

The deepest point in Lake Erie is 210 feet (64 meters), while the average depth is 62 feet (19 meters). The lake has a water retention time of 2.6 years, the shortest of all the Great Lakes.

More than 12,000 years ago, the basins of the individual Great Lakes were cut from soft Paleozoic limestone. However, the glaciers were largely unable to cut through the harder dolomite at the west end of Lake Erie, making this end of the lake very shallow, with depths averaging only 30 feet (9 meters). The central and eastern parts of Lake Erie lie on beds that are tilted to the south. These basins were carved from softer Devonian shales and are deeper than the western basin: up to 60 feet (18 meters) for the central basin and 80 feet (24 meters) for the eastern basin. In the narrow eastern part of the basin, where the angle of tilt is steeper still, the Devonian shales were eroded even more, to form the deepest basin, at 210 feet (64 meters). There are 31 islands in Lake Erie (13 in Canadian waters, 18 in the United States), most of them in the western basin of the lake.

Rich Biota

High nutrient levels make Lake Erie a biologically productive and species-diverse lake. Pelee Island, for example, at the western end of the lake, is home to rare insects, snails, mammals, birds, reptiles, and amphibians, including the endangered Lake Erie water snake (Coluber constrictor foxi) and the related blue racer (Coluber constrictor). Almost one-third of the vascular plant diversity of all Ontario is represented on Pelee and its neighboring islands. Pelee Island lays claim to one of the rarest of North American ecosystems: the alvar. Alvars are defined as communities of grasses and other herbaceous plants, accompanied by sparse shrubs that grow in extremely thin soils atop limestone or dolomite. These unusual ecosystems, some dotted with trees, are found in an arc roughly following the limestone and dolomite of the Niagara Escarpment.

Pelee Island lies at the confluence of two bird migration routes, is a significant stopover site for more than 70 species of migrating birds, and is designated as a Globally Important Bird Area. Pelee also is a temporary rest stop during the fall migration of monarch butterflies. Thousands of monarchs rest and feed there before continuing their long trek across the open water of the Great Lakes.

Lake Erie has sustained an important commercial and sport fishery for a succession of species since the 1800s. Most recently, yellow perch and walleye have been the most economically important species. Among its native fish are walleye, sucker, yellow perch, channel catfish, drum, blue pike (now extinct here), northern pike, small-mouth bass, white bass, lake sturgeon, gizzard shad, and emerald shiner. Among the introduced fish species are rainbow trout (steelhead), rainbow smelt, brown trout, alewife, sunfish, coho salmon, carp, round gobies, and sea lampreys. Asian carp are species of great concern, capable of causing ecosystem damage as they invade.

Radical changes in Lake Erie during the 1990s raised concerns about the future and predictability of the fish communities. Walleye stocks declined by about 80 percent from their maximum levels in the 1980s, and the supply of smelt to the commercial fishery in eastern Lake Erie declined by about 60 percent. Habitat for the fish is shrinking, especially in the central basin of the lake where the bottom layer of water has greatly reduced oxygen levels. Populations of fish-eating birds such as ducks, loons, and mergansers have been depleted from botulism poisoning. Such changes have been linked to a variety of factors, but increasing urban and suburban development pressures have led to problems with sewage overflows and nonpoint source pollution from agriculture.

The invasion of zebra and quagga mussels changed the way nutrients were cycled and the timing of nutrient availability in Lake Erie. These mussels reject blue-green algae, but consume green algae and nutrients, and then release nutrients in their fecal pellets late into the summer, when nutrient levels would normally be dropping. This process crashes populations of the green algae that normally would be available to zooplankton, which are a good source of food for juvenile sport and commercial fish and other small fishes. Concentrations of blue-green algae also can lead to taste and odor problems with drinking water from the lake.

Water Condition

Before 1950, Lake Erie was relatively clean and clear, and had low to moderate nutrient levels. In the 1950s, that changed: The water became so overloaded with phosphorus from wastewater plants, agricultural runoff, and industrial processes that massive diatom blooms developed and used up the lake's stores of silica, which these algae need to build their intricate cell walls. The diatoms were replaced with green algae, which are more dependent on phosphorus and nitrogen rather than silica.

As phosphate levels increased even further, the green algae blooms became so extensive that they used up the nitrogen and began to die. The phosphates released from these dead algae fed generations of blue-green algae (cyanobacteria) that could harvest their own nitrogen from the air and water. The cyanobacteria, in turn, became so dense that the surface layers began to shade the deeper ones. This resulted in the deaths of algae at lower depths. These cells sank to the bottom, eventually covering it in thick decaying layers. Their decomposition consumed large quantities of oxygen, causing dead zones.

The normally abundant mayfly larvae, which live and feed in the bottom sediments of clean lakes, completely died out at this stage; their demise led to an onslaught of species of worms that thrive in the anoxic conditions. Native fish that fed on the mayfly nymphs, such as chub and cisco, began to die off, allowing invasive species such as carp and alewives (which also tolerate lower oxygen levels) to thrive.

During the 1960s, Lake Erie was often called a dying lake or a dead lake. In July 1969, Ohio's most polluted river, the Cuyahoga, became so loaded with oil and debris that it caught fire in Cleveland's factory area. The Federal Water Quality Administration began a $1.5 billion municipal sewage-treatment program for the Lake Erie basin. Detergent manufacturers decreased the amounts of phosphates in their products, which had previously found their way into the lake via sewage treatment plants. The same year, Lake Erie was found to be polluted with the toxic insecticide DDT, and more than 64,000 pounds (29,030 kilograms) of coho salmon were seized from commercial fisheries on a charge that the fish were contaminated with DDT. Later, the even more poisonous chemical dioxin was found in the lake. Both these toxins had significantly harmful effects on fish and birds.

Further Threats

Lake Erie had been damaged severely, but its rapid rate of water exchange allowed it to flush the pollutants through the Niagara River and out to the Atlantic Ocean. With cleaner waters, the ecological community began to recover. However, the recovery still faces many complex obstacles. Experts say that to combat the toxic algae blooms in Lake Eric, new regulations for farmers are needed. Rules must be made limiting two main sources of phosphorus that feed the algae: chemical fertilizers and livestock manure. As of 2020, Ohio's Environmental Protection Agency planned to establish a "total maximum daily load" as to how much phosphorus is allowed to flow into the lake. In 2023, the EPA approved Ohio's plan for a maximum daily load of phosphorus for the Maumee River Watershed, which flows into the western basin of Lake Erie.

Mostly due to human carelessness, Lake Erie has become home to an increasing number of nonnative plants, animals, and microorganisms that threaten the balance of the entire ecosystem. The zebra mussel, quagga mussel, spiny water flea, fishhook water flea, goby, grass carp, and European water milfoil, among many others, have begun once again to threaten the lake. Blue-green algae such as Microcystis is again forming a thick scum on the lake and producing toxins that can be fatal to animals that drink the contaminated water. By 2013, the algae coverage was almost back to the levels that caused such problems in the 1960s, and environmentalists were concerned that factors such as climate change and changes in agricultural practices would make the lake harder to clean up a second time. From 2010 through 2017, the size of the lake's dead zone ranged from 20 to 35 percent of the lake's total area. According to the EPA, the size of the dead zone continued to grow in the 2020s. In 2024, Lake Erie recorded its earliest toxic bloom. In 2022, Lake Erie was the most polluted Great Lake.

Climate change also will impact the area, which could lead to a steep drop in water levels over the coming decades, a change that could cause the lake's surface area to shrink by up to 15 percent. If that occurs, the drop could undo years of shoreline abuse by allowing water to resume its natural coastal circulation, which has become blocked by man-made structures over the years. If the water level of the lake drops to that extent, there could be a significant positive impact on plant-loving species such as northern pike (Esox lucius), muskellunge (Esox masquinongy), and largemouth bass (Micropterus salmoides), particularly if subsequent submersed vegetation accompanies the change.

Bibliography

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