Lake Needwood water has harmful algae

Visitors to Rock Creek Regional Park have been warned to avoid contact with the water in Lake Needwood because it contains harmful algae.

The Montgomery County Department of Parks and the Maryland Department of the Environment suggest people not drink the water, avoid swimming in it and keep pets away because the lake contains strains of microcystin, a toxin in algae that can damage the liver and cause gastrointestinal discomfort when ingested and minor skin irritation upon contact.

Animals that drink water infected with microcystin can develop serious health problems, officials said.

Kelli Holsendolph, a parks department spokeswoman, said warning signs were posted around the lake in Derwood early last month, and a precautionary advisory has been on the parks system Web site since July 9.

Holsendolph said environment officials took water samples last month and will return to the lake next month to check algae concentration levels.

"MDE has informed us that we can expect the problem to persist for the rest of the season," she said.

Holsendolph said activities are continuing around the lake, including boat rentals, and visitors have not been deterred.

Doug Redmond, an aquatic biologist in the Park Planning and Stewardship Division of the parks department, said he and other county and state environmentalists are uncertain how long the algae bloom has been in the lake.

"The first time we were aware of the problem was last summer," Redmond said.

He said a park patron who is an expert on blue-green algae took samples and contacted MDE.

Redmond said MDE researchers tested samples of the bloom and identified the bacteria as microcystis, which produces microcystin.

According to the Maryland Department of Natural Resources, annual late-summer blooms of microcystis have been found in the tidal freshwater portions of the Potomac River. Larger-than-normal blooms occurred in the upper Chesapeake Bay and its tributaries in August and September 2000. Officials have attributed those blooms to greater-than-normal amounts of fresh water and nutrients entering the bay.