Lake Erie Ecosystem Structure, Function, and Change
Denise McSalters
SCI 256
November 13. 2013
University of Phoenix

Lake Erie Ecosystem Structure, Function, and Change
Carved out by glaciers during the last ice age the Great Lakes contain 20% of the earth’s fresh water. The lakes provide the majority of the basin’s human population with drinking water, commerce and recreation. Lake Erie is the smallest of the Great Lakes, relatively shallow, and is exposed to prevailing winds. Lake Erie ecosystem supports a diverse group of aquatic and land-dwelling organisms who use the ecosystem during important life stages. The lake support high production of both residential and migratory species and is a center for regional biodiversity. (US Department of the Interior; US Geological Survey, 2013)
Because Lake Erie is exposed to prevailing winds, it is particularly susceptible to intense wave actions and wind-generated changes in the lake level. The “seiches” or changes in the lake tides interchangeably flood and drain the coastal wetlands systems. The costal wetland systems encompass southeastern Michigan, northwest Ohio and southern Ontario. The Watershed is almost completely urban or agricultural. The major urban cities are Toledo, Detroit, Cleveland, and Buffalo. (US Environmental Protection Agency, 2013)
The most obvious forcer of Lake Erie ecosystem change was due to the input of excessive amounts of phosphorus from mainly agriculture and water treatment plants. At maximum levels in 1960’s and 1970’s the excessive phosphorus input, evidence for cultural eutrophication in the form of algal biomass and growth, harmful algal blooms and hypo limnetic hypoxia/anoxia were present throughout the lake. It is argued that the degradation of closed homogenous systems like the Great Lakes indicated that the system remained relatively unchanged with regard to the state before disturbances by humans. Once disturbed, the systems were unable to maintain their function as compared to before the disturbance. (Conroy & Culver, 2005)
After the passage of the Great Lakes Water Quality Agreement of 1978, phosphorus input decreased to acceptable levels as set forth in the Agreement. With the changes and the decrease in phosphorus levels algal biomass and harmful algal blooms decreased and oxygen depletion levels decreased. These changes indicated that the lake was shifting toward a less eutrophic state or less excessive growth of algae resulting from contamination of nitrogen and/or phosphorus compounds and more toward a mesotropic state or a state with good clarity and average level of nutrients. The shifting from a eutrophic state toward a mesotropic state is also affected by physical processes as rainfall amounts, warmer lake temperatures, storm frequency, and wind strength along with other factors. (Conroy & Culver, 2005)
By identifying ecological areas of strong biodiversity and provide protections for those areas is a way of restoring and managing the ecosystem of Lake Erie. Continue to protect the aquatic system of the lake by enforcing the Great Lakes Water Quality Agreement of 1978. Monitor lake levels and alternating the water table from irrigation, mining excavations, and wet land drainage to reduce the stress on the ecosystem. Reduce human induced stressed on the ecosystem by stopping the misuses of the land water and other natural resources. (US Environmental Protection Agency, 2013)
Walleye decline in the 1990’s was blamed on the Dreissenid mussel commonly known as the zebra mussel and other invasive species that altered the natural environment of Lake Erie. (Barus, 2008) The invasion of the zebra mussel at densities up to hundreds of thousands per square foot represented a new connection to the food web in Lake Erie. Zebra mussel consumes phytoplankton and my remove up to 25% or the algal standing crop in one day and their waste material are excreted back into the water. The excrement consists of phosphate-phosphorus and ammonia-nitrogen which is attributed to the excessive growth of cyanobacteria. Too many nutrients have caused Lake Erie’s central basin to become in essence a “dead zone” and causing steep declines in fish populations. (Conroy & Culver, 2005)

References
Barus, D. (2008). Wall to Walleye in Lake Erie. New York State Conservationist, 62(6), 10-12. Retrieved from http://search.ebscohost.com.ezproxy.apollolibrary.com/login.aspx?direct=true&db=8h&an=32726180&site=ehost-live
Conroy, J. D., & Culver, D. A. (2005). Do Dreissenid Mussels Affect Lake Erie Ecosystem Stability Processes? American Midland Naturalist, 153(1), 20-32. Retrieved from http://search.ebscohost.com.ezproxy.apollolibrary.com/login.aspx?direct=true&db=8gh&an=15716554&site=ehost-live
U.S. Department of the Interior, U.S. Geological Survey. (2013, August 1). Costal Ecosystems. Retrieved from http://www.glsc.usgs.gov/coastal-ecosystems
U.S. Department of the Interior, U.S. Geological Survey. (2013, August). U.S. Geological Survey - Great Lakes Science Center. Retrieved from http://www.glsc.usgs.gov/coastal-ecosystems/coastal-ecosystems-community-dynamics/assessment-benthic-fauna-western-lake-erie
U.S. Environmental Protection Agency. (2013, September 25). Conservation of Biological Diversity in the Great Lakes Basin Ecosystem: Issues and Opportunities. Retrieved from http://www.epa.gov/ecopage/glbd/issues/intor.html