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Study: Toxic Algae Blooms Help Create Their Own Favorable Conditions

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Last summer, cyanobacteria made the news when a toxic algae bloom in Lake Erie shut down the city of Toledo, Ohio’s water supply. In Kentucky, similar conditions meant that vacationers at 15 lakeswere greeted by warnings to avoid direct contact with the water, if possible. And many scientists have said that as the earth’s climate changes, instances like these could become more frequent.

Now, a new study suggests that these harmful blooms may play an active role in creating their own favorable conditions in lakes.

Cyanobacteria are toxic blue-green algae that can cause illness and irritation in humans and animals. They thrive in warmer waters with ample amounts of nutrients like nitrogen and phosphorus. Last summer, state and federal regulators issued advisories for 15 lakes in the commonwealth that were known to have harmful algal blooms.

But Dartmouth College biology professor Kathryn Cottingham said the problem isn’t limited to Kentucky, the region, or the country.

“The general perception is that worldwide, cyanobacteria blooms are on the rise,” she said. “Likely due to a combination of how we’re changing the landscape and how nutrients leave land and go into the water, and changes in our climate.”

Nitrogen and phosphorus occur naturally in the environment. But oftentimes, excess amounts end up in watersheds because of runoff from sources like fertilizer-laced agricultural fields and overflow from sewage treatment plants.

The algae feed on these nutrients. Buta new study authored by Cottingham and others suggests that once algae get a toehold in a watershed, the organism isn’t limited to consuming the nutrients that are already in the water.

“They are capable of creating new nitrogen in the system by accessing nitrogen that’s currently in the atmosphere in forms that other organisms can’t use,” Cottingham said. “They bring it into their bodies and they turn it into a form of nitrogen that can grow more of them, or more of somebody else.”

Ditto for phosphorus, which Cottingham’s study suggests the cyanobacteria can access from sediment and deeper water—places that other similar organisms can’t reach. The cyanobacteria can create a positive feedback loop, which makes it harder to eradicate the problem.

“That’s the big concern right now, is that once you get these cyanobacteria with their ability to access these pools of resources that other species can’t, they make life better and better for themselves,” Cottingham said.

She said her research suggests that getting rid of algal blooms once they’re established will take more than just limiting the typical external loads of nitrogen and phosphorus in watersheds. She said the best solution for watersheds with low nutrient levels and no sign of cyanobacteria is making sure that nitrogen and phosphorus pollution never gets into the water in the first place.

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