The amount of sediment you see flowing into Lake Erie from the Maumee River could predict the size and scale of harmful algal blooms in late summer, according to a new study from the University of Toledo. Ohio Sea Grant researcher Dr. Tom Bridgeman has found a connection between the two phenomena, determining that the sediment plume, in fact, creates a perfect incubator for the blue-green algae.
Bridgeman and his graduate student Justin Chaffin collected Microcystis samples during a large bloom that took place in August and September, 2008. Through testing, they verified that muddiness in the water acts as a protective shield for the cyanobacteria, particularly when the water is mixed by breezes blowing across Lake Erie’s surface.
Because Microcystis has the ability to regulate its buoyancy, more than 90% of the cyanobacteria can be found at the surface on calm days, further shading other varieties of algae. However, bright sunlight will actually damage the blue-green algae, regardless of the amount of mud in the water.
"On calm, sunny days, Microcystis floating on the surface became damaged quickly, showing loss of up to 50% of photosynthetic capacity in samples collected between 10 a.m. and 2 p.m.," Chaffin explains. "Even after 2 to 5 hours of recovery time in the dark, traveling to the lab for testing, much of this damage was still unrepaired."
Chaffin also determined that the Microcystis had plenty of nitrogen but were still phosphorus deprived, indicating that phosphorus levels determine how much the blue-green algae will grow. The result underscores the importance of determining the source of the phosphous that has plagued Lake Erie for decades, in addition to limiting the amount of sediment that gets into the river by implementing erosion controlling management practices.
To read more about this Ohio Sea Grant-funded research, visit http://ohioseagrant.osu.edu/products/tj8wu/twine-line-summer-fall-2009