Toxic algae return to Lake Erie

Zebra mussels, a non-indigenous species to North America, may be promoting blue-green algae blooms

June 3, 1999
Web posted at: 4:10 PM EDT

Microcystis, a blue-green algae that is harmful to humans and deadly to plants and fish, has returned to a small area of western Lake Erie after a 10-year absence. Researchers are examining whether the reappearance of Microcystis might be associated with the recent arrival of zebra mussels, a non-native species that was introduced to Lake Erie from Russia in 1986.

At first, the return of Microcystis baffled many researchers. It was discovered that high phosphorus levels in Lake Erie, caused by fertilizers, laundry detergent and human sewage caused the large outbreak of the algae in the 1970s. Phosphorus, is one of the most vital nutrients necessary for Microcystis growth and, as a result, millions of dollars were spent to destroy the algae by reducing phosphorus levels in Lake Erie.

By the late 1980s, the fearful blooms had ceased. So a recurring Microcystis outbreak in 1995 caught many people by surprise.

David Culver, Professor of Zoology and Environmental Studies at Ohio State University, is looking into the matter in collaboration with 12 other researchers. He explains that the re-occurrence of Microcystis could be due to a change in phosphorus levels, or it could be due to the possibility that the zebra mussels are recycling phosphorus faster.

Culver believes the zebra mussels are using the phosphorus over and over again. "So a little bit (of phosphorus) goes a long way," he said. "Small changes in the reuse oh phosphorus can make it much more available."

The zebra mussels may be impacting Microcystis blooms in two ways, Culver says. "By recycling nutrients that normally would have spent more time in sediment, provides more phosphorus for further algae growth." Secondly, "the zoo mussels remove Microcystis from water columns in pseudo feces, which are more readily accessed by bottom dwellers, which are in turn eaten by fish." This possibility would provide the Microcystis with better access to the food chain.

"One of the reasons we are really interested in this is because zebra mussels are continuing to expand their presence in Lake Erie. If zebra mussels are responsible for the blooms of Microcystis, we should expect the blooms to become more frequent."

And that could be really bad news as Microcystis causes harm to other populations, especially humans. In people, the algae can cause vomiting, diarrhea and hepatitis-like symptoms, including intestinal cramps and liver problems.

Culver said many cities depend on water from Lake Erie. 'You can't just take water, chlorinate it and remove the toxin from Microcystis. Cities using water from Lake Erie for drinking will have to use special measures to remove the toxin."

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