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Another reason why green lakes are not a good sign

This photo of Microcystis, a kind of cyanobacteria, was taken in Lake Erie.
Rebecca Williams
Michigan Radio
Cyanobacterial bloom on Lake Erie.

When you think about greenhouse gasses that are driving our warming climate, maybe you think about power plants or your car. But lakes can release greenhouse gasses, too, and the amount of nutrients that get into lakes from farms and cities matters.

John Downing directs the University of Minnesota Sea Grant and he's a scientist at the Large Lakes Observatory. He says lakes release a lot of gas normally.

“Lake Erie, for example, gives off about as much carbon dioxide, right now, as all the cars in Detroit do,” Downing says. “So the carbon dioxide coming out of lakes is really important globally.”

In a new study, Downing, along with coauthors Tonya DelSontro and Jake Beaulieu, found eutrophication-- excessive plant and algae growth -- in lakes increases the amount of greenhouse gasses that are emitted.

“The effect gets really large,” he says. “So large that, in fact, maybe some of our efforts to curb greenhouse gasses would be sort of negated by the increase from green lakes. It’s another reason to keep lakes from getting green, basically, is that it can have a big effect on the atmosphere.”

Downing says phosphorous that runs into lakes from farms, yards, and sewage, is what concerns him most. He says cutting back on fertilizer, adding buffer strips near waterways, and making sure septic systems at lake cottages are working properly are all good things to do.

You can listen to the interview with John Downing above.

Rebecca Williams is senior editor in the newsroom, where she edits stories and helps guide news coverage.
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