The US National Oceanic and Atmospheric Administration (NOAA) predicts a significant late-summer algae bloom in Lake Erie, which could threaten water supplies and possibly prompt regulation of regional phosphorus fertilizer consumption.
The NOAA forecast released on 10 July placed this year's bloom severity below last year's levels, but agencies are still concerned with the ecological harms of a potentially significant algal bloom. Algae blooms are responsible for releasing harmful toxins that threaten water supplies and can also cause economic harms to local communities that are heavily reliant on fishing and tourism, according to the NOAA.
The Ohio Phosphorus Task Force II, which is responsible for assessing phosphorus runoff and its contribution to algae growth, is targeting fertilizer runoff as a leading contributor to higher phosphorus levels that prompt algal growth.
"In the western basin of Lake Erie, there are roughly four million acres of crop land surrounding the Sandusky and Maumee River that potentially contribute to nutrient runoff," said Ohio Phosphorus Task Force co-chair Kevin Elder.
Elder said that the research conducted by the Heidelberg Water Quality Lab indicates less phosphorus is coming from point sources like sewage plants and more is coming from non-point sources like the watershed from large-acreage agricultural activity during increasingly frequent rainstorms.
A 2011 study conducted by the US Department of Agriculture's (USDA) National Resources Conservation Service (NRCS) estimated that phosphorus from cultivated cropland represents 61pc of total phosphorus from all sources delivered through the Lake Erie basin.
Despite farmers meeting the total phosphorus reductions outlined by the Great Lakes Water Quality Agreement, Elder said that an increasing portion of phosphorus is dissolving and accessible for algae to use.
"Previously, the rule of thumb was that phosphorus once was in the soil, it didn't move but now we're seeing that 30 to 40 percent is coming out of the watershed and is coming through the tile drainage," USDA researcher Kevin King said.
King is involved in edge-of-field research in order to determine the scale of surface and subsurface nutrient drainage occurring in the Western Lake Erie basin. He has found that over-application and a lack of soil sampling is likely to blame.
"There are farmers that are probably applying too much and aren't accounting for what's in the soil," King said. "Some of the preliminary data that is collected shows that less than five percent of what applied is coming off the field."
Local authorities are attempting to curtail phosphorus runoff by encouraging responsible fertilizer management practices. Ohio Senate Bill 150 requires farmers with more than 50 acres to attend a fertilizer application course and become certified 30 September 2017.
This forecast marks the third annual outlook released by the NOAA to evaluate algae blooms for Lake Erie. Since 2008, the NOAA has issued weekly harmful algae bloom bulletins assessing the situation through the National Centers for Coastal Ocean Science.
Ohio State University's Sea Grant program, Heidelberg University, University of Toledo and the Ohio EPA will continue to monitor the bloom by taking samples for the duration of the summer.
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