Expert: Warming means more algae

Pond scum linked to illness in humans

Add this menace to the list of looming environmental disasters blamed on climate change: more pond scum.

The blue-green algae that coats stagnant ponds and blooms in water reservoirs in hot summer months will thrive in a changing climate, said Hans Paerl of the UNC-Chapel Hill Institute of Marine Sciences.

And more pond scum could trigger more sickness. The 40 to 50 harmful species of the blue-green algae have been linked to digestive, neurological and liver diseases in humans. Municipal water plants across the United States spend millions to treat it.

Blue-green algae, known scientifically as cyanobacteria, are more prevalent in developing countries but occur in water bodies around the world from the Great Lakes to Florida's Lake Okeechobee to Falls Lake, Raleigh's water reservoir.

"This is a worldwide problem," said Paerl, co-author of a perspective piece Thursday in the journal Science.

Stimulating algae

It's well known that nitrogen and phosphorus in fertilizer runoff and in treated sewage feed blue-green algae growth. Now, Paerl suggests, scientists can factor in temperatures and global warming as well.

Warmer weather has created longer growing seasons. It has allowed the blue-green algae range to expand from Florida northward throughout the Southeast. When algae blooms die and decompose, they pull oxygen from the water and can cause fish kills.

"The temperature change is playing into hands of blue-green algae," Paerl said. "We have to be more diligent in reducing nutrients to slow down expansion into lakes that are now amenable to these blooms."

Paerl said water bodies in North Carolina have long had issues with algae blooms.

"We've been pretty successful at managing those," Paerl said. "It has become more prevalent in North Carolina reservoirs and lakes. Fortunately, it hasn't become as widespread as in Florida."

Wayne Carmichael, a toxicologist who serves on a national panel studying harmful algal blooms and a retired professor from Wright State University in Dayton, Ohio, said Paerl's argument that climate change would be a catalyst for expanding harmful algal blooms is logical because the blooms thrive in warmer temperatures.

"He's linking it, but he is not proving it," Carmichael said. "The blooms are increasing in intensity. It's like one of these arguments that is obvious, but you haven't proven it."

Ken Hudnell, a former neurotoxicologist at the U.S. Environmental Protection Agency's National Health and Environmental Effects Research Laboratory, in Research Triangle Park, and editor of a recent book on the state of the science about harmful algae, agreed that algal blooms will become more frequent and widespread. Hudnell is now vice president and director of science for SolarBee, a company that makes solar-powered equipment to circulate water to prevent blooms.

"The government is aware of this increasing problem," Hudnell said. "The incidence does appear to be worldwide due to increased nutrients in water. The government is now at a stage of trying to develop a national research program and gather information to develop regulations."