The 2011 Lake Erie bloom was composed almost entirely of toxic blue-green Microcystis algae. Concentrations of mycrocystin, a liver toxin produced by the algae, peaked at about 224 times World Health Organization guidelines, according to the researchers.
In addition to meteorological conditions, other factors contributed to the 2011 Lake Erie algae bloom. Chief among them is the widespread adoption, since the mid-1990s, of no-till farming and other agricultural practices that have increased the availability of a type of phosphorous, known as dissolved reactive phosphorous or DRP, that promotes algae growth.
In no-till farming, crops are planted without plowing by inserting seeds into small holes. The technique reduces erosion but leaves high levels of phosphorous-bearing fertilizer in the upper surface soil, where heavy rainstorms can wash it away. Trends toward autumn fertilizer application and surface broadcasting of fertilizers also create conditions for enhanced phosphorous runoff.
Unless there's a significant shift away from these practices, runoff from farmland in the Maumee River watershed and other Western Basin watersheds will likely continue to provide the nutrients needed to trigger massive Lake Erie algae blooms.
In addition, the current emphasis on producing corn for ethanol production, as well as a trend in the Midwest toward declining acreage reserved for conservation purposes, is likely to exacerbate the problem, said Michael Moore, a professor of environmental economics at U-M's School of Natural Resources and Environment and one of the paper's co-authors.
"Corn is the crop on which phosphate-based fertilizer is most heavily applied," Moore said. "So the intensification of corn production is a problem, and part of the solution would
|Contact: Jim Erickson|
University of Michigan