Microcystins are a class of toxins produced by certain freshwater cyanobacteria, often called blue-green algae. They are considered a public health concern. The algae blooms in Lake Erie are caused by cyanobacteria.
The survey conducted by the USGS included five states, Alabama, Georgia, North Carolina, South Carolina and Virginia. “This was the first systematic stream survey of algal toxins in the southeastern United States,” said Keith Loftin, the USGS research chemist who led the study.
Loftin pointed out the importance of the study because it provided a better understanding of the microcystin’s occurrence in aquatic ecosystems in flowing waters. In a 2009 study, it was found that a warming planet could act as a catalyst for the expansion of toxic algae blooms.
Information from previous studies performed from 1993 to 2011 provided data on streams in the Southeastern United States that indicated that 74 percent of streams tested had cyanobacteria, a form of algae capable of producing microcystins. However, at that time, the research did not include the study of microcystins. The finding of microcystin-producing cyanobacteria provided critical evidence that enabled the scientists to prioritize and design their subsequent research.
The microcystin levels found in this latest study did not exceed the World Health Organization’s (WHO) moderate risk thresholds (10 µg/L) in the streams sampled. The maximum level of microcystins found by the USGS measured 3.2 µg/L, well below the WHO risk threshold level.
Further studies are needed to understand the potential effects of microcystins on the environmental and any related health risks to ecosystems, lakes and drinking water reservoirs. This particular survey is the first of several regional surveys to be conducted on algae toxins.
The next project will look at the pacific Northwest, with future projects planned for the Northeastern U.S. and California. All the surveys will help in understanding the nature of cyanobacteria toxins in a wider variety of aquatic ecosystems.
