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Researchers discover high levels of algal toxins in Indiana lakes

November 16, 2009
A team of SPEA researchers, led by professor Bill Jones, has discovered detectable levels of microcystin, a toxin produced by several common species of cyanobacteria, in 68 percent of a sample of Indiana lakes and reservoirs. That's higher than twice the rate at which microcystin was found in a nationwide survey conducted by the U.S. Environmental Protection Agency. The national survey found microcystins in 32 percent of lakes and reservoirs.

The SPEA team was contracted by the EPA and the Indiana Department of Environmental Management to conduct the sampling of 50 Indiana lakes. Samples were sent to a variety of laboratories around the country for analysis.

The Indiana sampling was conducted in the summer of 2007 as part of the National Lakes Assessment (NLA), a survey of the nation's lakes undertaken by the EPA. The study sampled more than 1,000 lakes and reservoirs more than 10 acres in size to get an unbiased, statistically relevant snapshot of water quality in lakes and reservoirs in the U.S. The EPA recently released the results.

The NLA included a comprehensive assessment of water, sediments and shallow water habitats in the nation's lakes and reservoirs. While the NLA represented the first statewide assessment in Indiana that included microcystins, SPEA has assessed water quality in Indiana lakes for 21 years under the Indiana Clean Lakes Program (http://www.indiana.edu/~clp/).

Cyanobacteria, also called blue-green algae, are primitive organisms that grow in ponds and lakes, causing the water to turn pea-green color and sometimes forming surface scums. They can produce toxins that have been linked to animal deaths and fish kills. Last week, the Environmental Quality Service Commission of the Indiana legislature directed state environmental, health and natural-resource agencies to devise a strategy for monitoring blue-green algae levels in state waters.

Levels of microcystin found in Indiana lakes ranged from 0.11 micrograms per liter of water to 3.4 micrograms per liter. There are no U.S. standards for algal toxins in fresh waters, although the EPA is working to set standards. Several states post advisories on lakes when microcystin concentrations reach levels ranging from 6 to 20 micrograms per liter, considerably higher than those found in Indiana lakes.

"The most definitive conclusion we can make is that microcystins are widespread through Indiana, and they are present at a higher percentage of Indiana lakes than the mean for other states," Jones said. "These results provide further justification for developing a regular, statewide cyanotoxin monitoring program in Indiana."

Jones said that because the National Lakes Assessment relies on a single sample taken from the deepest water of each lake, there are several issues to consider in interpreting the results:
  • Cyanotoxin production varies throughout the summer, so the single sample may not represent the maximum concentration that was present.
  • Sampling in open water likely underestimates the true extent of toxin occurrence and magnitude. Winds are known to blow toxins to downwind shores.
  • One can't assume there is no risk based on single samples that found no toxin or only low levels.

For data on the levels of microcystin found in specific Indiana lakes, see http://www.indiana.edu/~iunews/lakeschart.pdf.