August 31, 2004 Foam on the Potomac River associated with a decline of the persistent summer blue-green algal bloom.

On August 23, Maryland Department of Natural Resources (MD DNR) and the Academy of Natural Sciences (ANSERC) encountered white foam covering the Potomac River from shore to shore near Maryland Point. ANSERC indicated the foam was concentrated over a stretch of approximately 3 km (nearly 2 miles) around Maryland Point and declined in concentration going upriver as far up as Mattawoman Creek.

The foam appears to be the result of the die-off and decomposition of a persistent blue-green algal bloom in the region this year. MD DNR has been tracking the bloom since bloom patches were first observed in the area in early June (see HAB News from June 11, 2004: "Blue-green algal blooms expanding in Chesapeake Bay tributaries since June 1."). Strong bloom conditions have been sustained on the river since mid-July over a stretch of nearly 30 miles primarily located in waters adjacent to Charles County, MD (see HAB News from July 22, 2004: "30 miles of Microcystis, 15 miles of blue-green algae surface scum on the Potomac River.").

On August 2, Maryland Department of the Environment (MDE) responded to a call regarding a 2 mile long by 10 foot wide streak of foam on Nanjemoy Creek, downstream of Maryland Point. The blue-green algae Microcystis and a diatom Melosira could be found in densities of 10,000 cells/ml and 11,000 cells/ml respectively when a sample of the foam was rehydrated. The most recent monitoring results from August 23 indicated the remainder of the bloom was concentrated between Indianhead and Smith Point. MDE investigated any possible connections to pollution events but found no evidence of significant compliance violations to alternatively account for the foam.

Pockets of blue-green algal blooms may be encountered during boating and other recreational activities. People should take common 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 viscera (internal organs) of fish caught in bluegreen 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 now a reportable illness so physicians should be reporting these to local health departments. The MD DNR in coordination and cooperation with DHMH and MDE will continue to monitor all blue-green algal blooms throughout the state. For up to date information on all of Maryland's harmful algal blooms and water quality, please visit Eyes on the Bay