Climate change and fertilizer runoff spell bad news for Lake Erie

It’s been a rough four years for Lake Erie. In 2011, there was a record-setting algae bloom on the lake. The following year Lake Erie experienced its largest ever “dead zone,” an area of oxygen-depleted water that chokes fish and plants. Then in August 2014 a toxic algal bloom near Toledo, Ohio forced the town to shut off its water.

A study published Tuesday in the journal Environmental Science and Technology found that these events weren’t bad luck. They were a result of weather patterns altered by climate change.

“Those three events put together tells a bigger story than any event individually,” said Anna Michalak, a researcher with the Carnegie Institution for Science and lead author of the study. “The last few years have been strangely consistent in how negative things have been.”

Algae blooms are a regular occurrence, fed by fertilizer runoff from lawns and farms. When the algae dies, it consumes a lot of oxygen, creating dead zones where fish and plants can’t survive. Until now, scientists believed these cycles were strictly a result of agricultural practices. But going over the past 28 years of data from the lake, Michalak and her colleague Yuntao Zhou found that the severity of these cycles is affected by how rivers fed the lake that year.

Heavy spring rainstorms dumped more water, and agriculture runoff, into the lake in 2011, which accounted for the massive algae bloom that year. But to her surprise, Michalak found the algae bloom of 2011 produced a very small dead zone. In 2012, the drought exacerbated the dead zone, with little water entering the lake from rivers and streams.

Historically, Lake Erie has been received the brunt of the negative impacts of changing land use and changing climate, Michalak said. Studying how Lake Erie responds to changes will help lake management protect the Great Lakes in the future.