Two Montgomery County lakes contain toxic mycrocystin

Lake Needwood is located inside Rock Creek Regional Park in Rockville. Photo: Wikimedia Commons

When it’s this hot and the lake looks this cool, you may be tempted to splash in shimmering waters. But, officials say don’t even dip a toe in.

“We have a blue-green algae bloom at Lake Frank,” says Jai Cole, an aquatic ecologist at the Department of Parks in Montgomery County. “It’s a cyanobacteria –a toxin produced by the cyanobacteria that is harmful to pets and humans.”

Lake Frank and Lake Needwood are toxic, showing higher than expected levels of a natural poison called microcystin. If you or your pet ingests too much it could damage the liver.

“It's basically what people consider 'pond scum' so when you see little scummy, film on the top –that’s what it is,” Cole says.

Cole says the blue-green algae is common and forms when run-off from human endeavors (think lawns, golf courses, etc.) drips into the manmade lake, boosting nitrogen and phosphorous. Combined with a warm, sunny summer and the result is excessive blue-green algae.

Courtney Pattee took her dog Norah to the park, only to have their trip cut short.

“Usually we go down to the water so we stayed the paved trail this time which was kind of a bummer,” Pattee says. “It made for a shorter outing certainly and a hotter one.”

Though officials warn residents not to go in the water, they continue to encourage residents to use the area.

“The lake itself is not closed, we're not closing it down to recreation,” Cole says. “You can consume fish caught from either lake as long as you cook the muscle meat. We don't recommend eating the organs.”

Cole added the algae usually clears out on its own, but could take months. If you do come in contact with the water, officials say don’t panic and simply wash the area.

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