Phosphorus runoff: A large contributor to problems in Western Lake Erie Basin.
Posted on April 1, 2015 by Christina Curell, Michigan State University Extension , Lois Wolfson, Steve Miller, Bruce MacKeller, Marilyn Thelen, Paul Gross, Shelby Burlew, Lina Rodrigues, Phil Kaatz
Western Lake Erie Basin, USDA-NRCS
Water is essential to all life on earth. When the quality of water is impaired every living organism is impacted. The problems associated with Lake Erie are examples of how agricultural practices, naturally occurring events, and other human activities can have an impact on water quality.
Lake Erie, considered the 11th or 12th largest lake in the world by surface area, is the shallowest of the Great Lakes averaging 62 feet in depth with a maximum depth of 210 feet. Due to its shallow depth it also is the warmest of the lakes and the most productive for the fishery industry. Approximately 95 percent, of the water that enters Lake Erie comes from the other Great Lakes and large rivers and tributaries from 5 states and the Providence of Ontario. The land that drains into Lake Erie from Michigan encompasses 5,800 square miles, 19 percent of the total land base in the Lake Erie basin. Twelve million people live within the Lake Erie watershed and 11 million of those residents get their drinking water from the Lake Erie Watershed. Because of its shallow depth, warm waters, and excessive input of nutrients from the surrounding land area, Lake Erie is particularly susceptible to algal blooms. Harmful algal blooms are causing the greatest concern. They are made up of what used to be called blue-green algae but are now referred to as cyanobacteria. These have been prominent in the Western Basin of the lake. Many cyanobacteria produce a toxin that can seriously affect human health if swallowed or cause skin rashes through body contact. They are also unsightly, not readily consumed by microscopic animals and can lead to decreased oxygen levels in the lake when they die and decompose.
Phosphorus is an essential nutrient for growth. However, many lakes in Michigan are often phosphorus limited, so additions of it result in increased production. As more phosphorus become available through activities on the land, more algae are produced. By mid to late summer, the cyanobacteria often begin to dominate the upper waters and can cause massive algal blooms. As summer continues, the algae and cyanobacteria begin to die and sink to the lake bottom, eventually resulting in a depletion of oxygen in the bottom waters as the plants die, and bacteria decompose the plant material.
While the Western basin of Lake Erie is most prone to harmful algal blooms due to its very shallow depth and warm water, the small lower layer in the Central basin experiences a “dead zone” due to the oxygen being depleted, becoming a problem for fish and other biota. This overall scenario becomes more intense not only due to phosphorus loading from the land but also due to warmer weather and an increase in the frequency of severe storms that can increase erosion and re-suspend the sediments in the lake. Studies have shown that the majority of loading occurs during storms.
Historically Lake Erie has had water quality issues that were attributed to phosphorus loading. The governments of Canada and U.S. joined forces to address the issue during the 1960’s. The preceding decades saw a decrease in the phosphorus concentrations, and in 1987 both governments signed the Great Lakes Water Quality Agreement that enabled a Lake-wide Management Plan to be developed.
Phosphorus comes from many sources. It is used in household products such as soaps, industrial products, in lawn fertilizers, and in agricultural products for crop production. Phosphorus also is found in municipal wastewater, storm drain systems, and septic systems. Incidents of direct discharges such as wastewater, industrial, and stormwater into the Lake Erie basin has led to water quality issues. These discharges have been monitored and in the past several decades the incidents have been decreasing. The challenge of reducing phosphorus loading is for the management of non-point source loading, contamination that cannot be directly related to a specific event, pipe or operation.
Non-point source phosphorus loading comes from both urban and rural landscapes. Phosphorus is found on soil that erodes or from surface runoff. Phosphorus can also leach through soil and enter tile drains that empty into a stream or river. Phosphorus, in the dissolved form, is 100 percent available to algae while phosphorus that is bound to soil is only 25 percent available for algae. Research has shown that the concentration of dissolved reactive P is now exceeding particulate phosphorus from several tributaries to Lake Erie. Annual dissolved phosphorus loads from the Maumee from 1975 to 1995 showed a decreasing trend. Since then, the trend has increased. There are many sites throughout the watershed that are monitoring dissolved reactive phosphorus levels in river and stream systems. It is estimated that half of the total phosphorus that is entering the Lake Erie watershed from the United States is coming from the Maumee River Watershed. This watershed like the other watersheds in the basin is heavily farmed.
Agriculture producers are encouraged to reconsider and fine tune their field practices to reduce/minimize phosphorus both as sediment and dissolved that can leave their fields. Michigan State University Extension and the Institute of Water Research have formed a Western Lake Erie Basin Agriculture team. In the upcoming months, we will be discussing and demonstrating specific recommended practices that farmers can use to reduce negative impacts from their farms on the water quality in Lake Erie. MSU Extension, in conjunction with agricultural organizations, will be sponsoring educational sessions and on-farm demonstration events during 2015 and 2016 in Southeast Michigan.
To learn more about Lake Erie, visit:
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