"When one considers their evolutionary history and the fact that they've persisted even through ice ages and asteroid strikes, it's not surprising they're extremely difficult to remove once they've taken hold in a lake," he said. "For the most part, the best we can do is to try to minimize the conditions that favor their proliferation."
Researchers lack an extensive historical record of bloom events and their associated toxicities to put current observations into a long-term context. However, Otten said, "If you go looking for toxin-producing cyanobacteria, chances are you won't have to look very long until you find some."
There are more than 123,000 lakes greater than 10 acres in size spread across the United States, and based on the last EPA National Lakes Assessment, at least one-third may contain toxin-producing cyanobacteria. Dams; rising temperatures and carbon dioxide concentrations; droughts; and increased runoff of nutrients from urban and agricultural lands are all compounding the problem.
Many large, eutrophic lakes such as Lake Erie are plagued each year by algal blooms so massive that they are visible from outer space.
Researchers studying cyanobacterial toxins say it's improbable that their true function was to be toxic, since they actually predate any predators. New research suggests that the potent liver toxin and possible carcinogen, microcystin, has a protective role in cyanobacteria and helps them respond to oxidative stress. This is probably one of the reasons the genes involved in its biosynthesis are so widespread across cyanobacteria and have been retained over millions of years.
Because of their buoyancy and the location of toxins primarily within the cell, exposure risks are greatest near the water's surface, which raises concerns for swimming, boating and other recreational uses.
Also, since cyanobacteria blooms become entrenched and usually occur every summer in impacted
|Contact: Tim Otten|
Oregon State University