Written by Larry Limpf
May 14, 2010
A task force studying the migration of phosphorus into streams and rivers and eventually into Lake Erie notes the problem is primarily affecting the lake’s western basin – particularly from the watersheds of the Maumee and Sandusky rivers.
If “significant” actions are taken, however, the lake can again recover as dramatically as it did in the 1980s, according to the recently released report of the Ohio Lake Erie Phosphorus Task Force.
Total phosphorus, including dissolved and particulate phosphorus, has long been a problem for the lake, the study says, and the earliest efforts to reduce phosphorus levels in the 1970s focused on reducing the dissolved phosphorus discharging from wastewater treatment plants.
Farmers across the region were also adopting practices such as no-till planting that reduced sediment erosion from fields and the phosphorus bound to it.
Consequently, a goal of reducing phosphorus levels by 11,000 metric tons was reached and conditions in the lake improved, according to the study.
Most monitoring programs, however, focused on total phosphorus levels. But a team of researchers at Heidelberg University was also tracking dissolved phosphorus and by the mid 1990s saw a trend of increased dissolved phosphorus loads to the lake from northern Ohio rivers.
The Ohio Environmental Protection Agency convened the task force in 2007 to compile research on the sources of phosphorus and their potential contribution to algal blooms, also known as cyanobacteria, in the lake.
Findings of the report include:
• Phosphorus levels are increasing from northeastern watersheds such as the Cuyahoga and Grand rivers but to a much smaller extent than from northwestern rivers.
• There are multiple sources of phosphorus loading but the most significant is runoff from agricultural applications such as common fertilizers and livestock manure. The task force’s primary concern was dissolved reactive phosphorus (DRP), a form that doesn’t attach to sediment. Also known as soluble phosphorus, DRP is more readily available for attachment to crops and algae than particulate phosphorus attached to soil and sediment. Manure and commercial fertilizer have relatively high concentrations of DRP.
• Farm management practices that focus on the timing, amount and method of applying fertilizers will have the greatest potential for reducing algal blooms in the lake’s western basin.
• Analyses are needed on the movement of sediment and fertilizers through stream systems and through lake estuaries, bays, and shorelines during and after storm runoff.
• The role of climate change and stronger storms in the area producing more runoff and the effect of invading species such as zebra and quagga mussels need to be examined.
The task force report and related documents is available at the Ohio EPA website.
Task force members include: Ohio Farm Bureau Federation, Heidelberg University National Center for Water Quality Research, The Ohio State University Environment and Natural Resources, OSU College of Biological Sciences, OSU Sea Grant, OSU Extension, U.S. EPA Great Lakes National Program Office, University of Toledo, U.S. Geological Survey, Natural Resource Conservation Service, Ohio Department of Agriculture, U.S. Department of Agriculture’s Research Service, Conservation Action Project and Henry County SWCD, Northeast Ohio Regional Sewer District, Ohio Department of Natural Resources Division of Soil and Water, ODNR Division of Wildlife, Case Western Reserve University, Ohio Lake Erie Office, Ohio Academy of Science/Ohio Fractured Flow Work Group, and Ohio EPA Division of Surface Water.
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