TOXIC ALGAE RETURNS TO LAKE ERIE
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 zebra 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."
Source: Environmental News Network 6/3/99
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