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Ohio Sea Grant College Program
and Stone Laboratory

Ohio Sea Grant and Stone Laboratory

Researchers Study Roundup as Possible Cause of Harmful Algal Blooms


Article By: Stacy Brannan, Published: April 27, 2009

 The herbicide Roundup may be contributing to the growth of harmful algal blooms in Lake Erie, according to Ohio Sea Grant researchers. Drs. R. Michael McKay and George Bullerjahn of Bowling Green State University are studying the impact of glyphosate, a phosphonate and the main ingredient in the commonly used herbicide, on the strains of blue-green algae found in Lake Erie.

 Phosphorus has long been known to act as fuel to blue-green algae, and efforts in the 1970s reduced harmful algal blooms and nuisance algae by limited phosphorus loading in the Lake Erie watershed. However, the last 15 years have seen an increase in the growth of the toxic blooms, contributing to an ever bigger Dead Zone in the lake’s Central Basin and massive fish kills each summer.

 Scientists have believed phosphonates to be inaccessible to plankton, but McKay and Bullerjahn have begun to look to glyphosate as a potential phosphorus source with funding from Ohio Sea Grant.

 “Our research is finding that Roundup is getting into the watershed at peak farming application times, particularly in the spring,” McKay explains. Their work has shown that glyphosate cannot be detected in the lake in April but can be found from mid-May through July, after crops are planted, which corresponds to the forming of the Dead Zone. They have also discovered that the blue-green algae, also known as cyanobacteria, are capable of using phosophonates.

 “It turns out that many cyanobacteria present in Lake Erie have the genes allowing the uptake of phosphonates, and these cyanobacteria can grow using glyphosate and other phosphonates as a sole source of phosphorus,” Bullerjahn says.

 McKay and Bullerjahn are now determining exactly what the algae do in a glyphosate-rich environment. “We know that blue-green algae native to Lake Erie can use the compound,” says McKay. “What we have not determined is the extent to which they are using it, and if you see a massive change in the micro-organisms in the lake.”

 If glyphosate is, indeed, found to be increasing the amount of algae in Lake Erie, researchers can create new pollution models to account for the additional phosphonates as a phosphorus source. Such models will help determine if the impact of glyphosate use warrants more attention and possible control. The study will conclude in 2010.

 To read more about this Ohio Sea Grant-funded research, visit

 The Ohio State University’s Ohio Sea Grant program is part of NOAA Sea Grant, a network of 30 Sea Grant programs dedicated to the protection and sustainable use of marine and Great Lakes resources. For information on Ohio Sea Grant and Stone Lab, visit .



Dr. R. Michael McKay, Professor, Bowling Green State University: 419.372.6873,


Dr. George Bullerjahn, Professor, Bowling Green State University: 419.372.8527,

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