Friday, September 2, 2011

Sources of toxic algae: farms, cities

Tracking phosphorus, courtesy Columbus Dispatch

Scientists know what causes the toxic blue-green algae that stain western Lake Erie every summer. 

It’s phosphorus, a byproduct of sewage, fertilizers and manure

At stake is Erie’s $10 billion-a-year fishing and tourism industry. Blue-green algae excrete liver and nerve toxins that can sicken people and kill pets, fish and other wildlife. The algae also help create an expanding oxygen-depleted “dead zone” in Lake Erie where fish cannot live.

Manure that rains wash off farms is considered the prime source of phosphorus in Grand Lake St. Marys, a 13,000-acre lake in western Ohio where the state has posted algae warnings for swimmers since 2009.

The current “bloom” of algae in Lake Erie has prompted health warnings at public beaches at Maumee Bay State Park and Kelleys Island…

Jeffrey Reutter, director of Ohio Sea Grant and Stone Laboratory of Ohio State University, said the Geological Survey’s findings don’t address the fact that the Detroit River supplies 80percent of Lake Eries water.

That much water, he said, dilutes all the phosphorus going into the lake and doesn’t create algae blooms. He said satellite images that show algae spreading from the mouth of the Maumee prove his point.

“The Maumee River, it brings in 3 percent of the flow to the lake but probably 40 percent of the (lake’s) sediment,” he said.

“You could make a big improvement in the Detroit River, but you’re still going to have the harmful algae problem in Maumee Bay.”more