Climate Change, Pollution Increasing Toxicity of Algal Blooms

Climate change and nutrient enrichment via pollution appear to be contributing to a rise in toxicity of some algal blooms in freshwater lakes and estuaries worldwide, researchers found.

Scientists from Oregon State University and the University of North Carolina determined that as nutrient enrichment increases, so do toxin-producing strains of cyanobacteria in harmful blooms.

At 3.5 billion years old, cyanobacteria are one of the world's oldest microorganisms, and are believed to have produced the oxygen that ultimately gave rise to life. So many years later, they've evolved so as to pose a threat to the life they originally helped create.

"Cyanobacteria are basically the cockroaches of the aquatic world," said Timothy Otten, a postdoctoral scholar in the OSU College of Science and College of Agricultural Sciences, whose work has been supported by the National Science Foundation. "They're the uninvited guest that just won't leave."

According to the Environmental Protection Agency's National Lake Assessment, at least one-third of the nation's 123,000 lakes greater than 10 acres may contain toxin-producing cyanobacteria. Exacerbating the problem are dams, rising temperatures and carbon dioxide levels, droughts and increased runoff of nutrients from urban and agricultural lands.

"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," Otten said. "For the most part, the best we can do is to try to minimize the conditions that favor their proliferation."

Cyanobacteria pose a risk to humans and animals, especially given their buoyancy, which drives them to the surface. Additionally, they become entrenched and occur every summer in affected areas, putting drinking water at risk.

"Water quality managers have a toolbox of options to mitigate cyanobacteria toxicity issues, assuming they are aware of the problem and compelled to act," Otten said. "But there are no formal regulations in place on how to respond to bloom events.

"We need to increase public awareness of these issues," he said. "With a warming climate, rising carbon dioxide levels, dams on many rivers and overloading of nutrients into our waterways, the magnitude and duration of toxic cyanobacterial blooms is only going to get worse."