Visitors to Lake Bernard Frank in Derwood should avoid touching the water, due to high levels of a harmful algae toxin known as microcystin, Montgomery Parks officials warned Monday.
If ingested, microcystin can seriously harm the liver of humans and pets. The toxin is produced by blue-green algae, or cyanobacteria.
A similar warning was issued in July for another body of water at Rock Creek Regional Park—Lake Needwood in Rockville.
Jai Cole, a natural resource specialist for Montgomery Parks, said portions of both lakes could be contaminated for the rest of the season.
“We will continue to monitor and update signs when the warning is lifted,” Cole said.
Dog owners are asked to keep their pets leashed and to keep them from drinking the water. People who fish are warned to only eat the properly cooked muscle meat of anything caught in the lake.
Swimming is prohibited at Lake Frank and Lake Needwood.