Toxic Algae Bloom Identified In Potomac River Tributary, Mattawoman Creek

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Dept. of Natural Resources Asks Potomac Watershed Residents For Help to Prevent Future Harmful Algal Blooms

Toxic Algae Bloom Identified In Potomac River Tributary, Mattawoman CreekIndian Head, MD —  Routine water quality monitoring by the Maryland Department of Natural Resources and the Morgan State University Estuarine Research Center recently identified high concentrations of blue-green algae, Microcystis, in Mattawoman Creek off of the Potomac River. The sample collected by DNR tested positive for toxicity.

“Excessive nutrient pollution in the water fuels these algal blooms, which are not uncommon in the freshwater and low salinity waters of the Potomac River. Harmful algal blooms such as these can be prevented if more people living in the Potomac River watershed take steps to reduce run-off pollution,” said Tom Parham, DNR tidewater ecosystem assessment director. “Some easy and affordable backyard solutions include planting native trees and rain gardens, using rain barrels, and refraining from fertilizing in the spring.”

After learning of algal toxin levels higher than typical acceptable standards for human and animal contact in water samples from Mattawoman Creek, Charles County issued a health advisory for the area encouraging people to take precautions to reduce the risk of illness or discomfort related to blue-green algal blooms:

The public should not swim in areas where a blue-green algae bloom is evident.

Do not drink water from any area with the appearance of a blue-green algae bloom.

If contact is made with problem water, simply wash off with fresh water.

In some cases, skin irritations may occur after prolonged contact. If irritations persist, see a physician or local health care provider.

Keep pets and livestock away from bloom areas.

Blue-green algal blooms may contain toxins that could be harmful or fatal to pets and livestock.

Do not eat internal organs of fish caught in blue-green bloom waters.

Inhalation exposure to blue-green algal bloom waters may result in irritation of the eyes, ears, nose and throat with extended recreational activity on such waterways.

Please note that illness associated with harmful algal blooms is a reportable illness and physicians should be reporting these to local health departments.

“We will continue to monitor the algal bloom.”

For up to date information on all of Maryland’s harmful algal blooms and water quality, please visit DNR’s Eyes on the Bay website at