It's thick as pea soup. And it's capable of killing you.
Microcystis, a toxic form of green algae linked to as many as 75 deaths in Brazil in 1996, is back again with a vengeance in Lake Erie. Once written off as a menace of the past, it has mysteriously reappeared in the lake this time of year almost every summer since 1995.
Last week, it started floating like a layer of green paint on portions of Lake Erie from Toledo to Cleveland. It's expected to hang around until mid to late September. It'll be especially visible when the sky is clear and bright sunlight causes millions of its tiny particles to bubble up through the water column and form mats on the lake's surface. Then, as temperatures cool and the autumn sky becomes gray, the stuff will fade away for at least another year, researchers said.
“It's uglier than I've ever seen it right now,” Tom Bridgeman, a University of Toledo research assistant professor, remarked yesterday as he boated toward the middle of a swath in Maumee Bay.
More than anything, the green water on the lake and on waves washing ashore along the shoreline has confused people like Terry Kolton, who lives in the North Shores area of LaSalle, Mich., near where South Otter Creek empties into Lake Erie.
“It's like green paint or green watercolor or something,” he said. “It looks real thick, like split-pea soup. I've never really seen anything like it.”
Aesthetics aside, toxic algae inhibit the growth of microscopic plants and animals important to the food chain of walleye, yellow perch, and other sportfish vital to the region's tourist-based economy. “It's definitely something we don't want out there,” said Dr. David Culver of Ohio State University, one of the lake's longtime algae researchers.
The immediate risk to the public is low. To get a lethal dose, someone would have to ingest a chunk of toxic algae about the size of a hockey puck. Less than that could result in nausea, vomiting, diarrhea, and other feelings of sickness.
Toledo and many other modern water treatment plants that draw water from Lake Erie have carbon-activated filters to destroy any algae that might make it into their systems, Mr. Culver said.
Bob Stevenson, Toledo utilities director, said the city water plant has not detected signs of microcystis. The algae was not seen yesterday in the vicinity of the Toledo water system's intake crib a couple miles out in the lake. He said it is unlikely to be drawn through because intake pipes are 13 feet below the water surface. Algae forms as it rises to the surface.
The timing of Thursday's massive power outage could be a cruel irony, given that it resulted in millions of gallons of raw sewage being discharged into Lake Erie and its tributaries just as the algae was coming into bloom. Detroit and Cleveland had especially heavy discharges of raw sewage.
“It sure didn't help,” Mr. Bridgeman said.
He said he saw clear water Friday near the Canadian side of Lake Erie. “We came back to the Ohio side and hit a band of [algae]. That's probably because the wind was blowing it toward the [Ohio] shoreline,” he said.
Microcystis fades from sight, but might not ever go away. Scientists believe it and two similar forms of toxic green-blue algae known as anabaena and aphanizomenon have been in Lake Erie for decades. But they have been held in check because of sewage treatment and other efforts to control phosphorus discharges from animal and human waste.
Now microcystis proliferates, but scientists have no clear answers. Many have their suspicions about the gradual increase in phosphorus from agricultural runoff into the Maumee River since 1997. Dr. Culver said it's a puzzle complicated by the fact that one of Lake Erie's other forms of toxic algae - aphanizomenon - was more dominant than microcystis before the landmark Clean Water Act of 1972 became the basis for many of today's modern sewage treatment improvements.
Dr. Culver said he used to believe zebra mussels were mainly responsible for the microcystis blooms, because of how they passed phosphorus through their systems. Now he believes the algae is being driven largely by the region's inability to control runoff from urban sprawl.
“If the lake is getting green again, that just means we'll have to work even harder,” he said.