Harmful Algae Bloom Confirmed in Potomac River Creek

August 2008 -- The Charles County, Md., Department of Health has issued a water advisory for Mattawoman Creek, a tributary of the Potomac River, after scientists collected water samples containing high concentrations of potentially harmful cyanobacteria, often called blue-green algae.

Microcystis aeruginosa is a naturally occurring type of cyanobacteria that can become harmful when it occurs in high concentrations or if it produces toxins. Nutrient-rich waters fuel the growth of Microcystis and many other algae.

A water sample taken from Mattawoman Creek on August 6 showed 247 micrograms per liter (ug/L) of microcystin, a hepatotoxin that can affect the liver. This toxin concentration is more than five times the safe recreational exposure level recommended for adults and nearly 25 times the recommended safety threshold for recreational exposure for children.

Microcystis blooms make the water look bright green, sometimes with a surface scum that looks like green paint. Do not swim in or drink water from areas where a cyanobacteria bloom is present. If contact with the bloom area is unavoidable, simply wash the area with fresh water. Pets and livestock should also be kept away from bloom areas to avoid the possibility of ingestion, which can lead to illness or death.

For more information about the Mattawoman Creek algae bloom, view the full water advisory from the Charles County Department of Health.

Visit Eyes on the Bay for real-time tracking of harmful algae bloom conditions in Mattawoman Creek and other tidal waters in Maryland.