Top Story

Lake Erie's toxic algae blooms: Why is the water turning green?

Since the late 1990s, Lake Erie has been plagued with blooms of toxic algae that turn its waters a bright blue-green. These harmful algae blooms are made up of cyanobacteria that produce the liver toxin microcystin. The blooms have led to public warnings to avoid water contact. In August 2014, for example, high microcystin concentrations were detected in drinking water from the lake. As a result, the water supply to 400,000 people in Toledo, Ohio, was shut down. Scientists at the center are conducting research to understand why harmful algae blooms happen in particular parts of Lake Erie. Their studies will help determine strategies to mitigate the blooms. In late summer, cyanobacteria called Microcystis are found in Lake Erie's open waters. From spring through fall, another cyanobacteria genus, Planktothrix, blooms closer to shore. Nutrients that fuel cyanobacteria blooms usually come from the nitrogen in agricultural runoff; the runoff makes its way into streams and rivers, eventually flowing into large water bodies such as lakes. Areas near shore are prone to nitrogen loss as summer progresses and the amount of rainfall -- and runoff -- decreases. Nutrients from spring rains spark Planktothrix blooms, but their persistence through late fall is due to the ability of the Planktothrix cyanobacteria to "scavenge" nitrogen from their environment better than Microcystis can.

Visit Website | Image credit: NASA