State regulators warn against spread of ‘rock snot’ algae

A thick, matted alga known as “rock snot” has invaded Gunpowder Falls in Baltimore County, and other area streams and rivers could be at risk.

Maryland Department of Natural Resources officials have set up stations along the falls where fishermen can clean their boots and equipment to prevent spreading the invasive species.

“We are trying to prevent the spread of it. Once you find it’s there, it’s too late,” said Jonathan McKnight, associate wildlife director at DNR.

An angler recently discovered didymo, or didymosphenia geminata, also called “rock snot,” in Gunpowder Falls, McKnight said.

The algae form extensive mats, attaching on stream beds by stalks that have a texture of wet wool, according to the U.S. Environmental Protection Agency. Didymo, which isn’t considered a human health risk, smothers the stream beds and affects freshwater fish habitats.

Now, state regulators are reminding people wading through Gunpowder Falls to sterilize their boots and gear in saltwater for one minute. Six wader sterilization stations have been set up near Gunpowder, and officials plan to set up stations along the Casselman, Youghiogheny and Savage rivers.

“If you go there with felt-soled waders and don’t wash them, you become a Typhoid Mary for this organism for the next stream you step in,” McKnight said, referring to a woman who inadvertently spread typhoid fever at the turn of the century.

“Nobody wants to be that person.”

Anyone wading in the river should then scrub away dirt and disinfect all equipment with a solution that is at least 5 percent salt, according to DNR.

Didymo can be a “pretty serious” invasive species for freshwater streams by decreasing the production of invertebrates, which trout rely on for food, said Ray Morgan, a professor at the University of Maryland Center for Environmental Science Appalachian Laboratory in Frostburg.

Didymo originally was found in Scotland and has been spread around the world, most recently in the Northeast and mid-Atlantic regions of the United States, according to DNR.

DNR officials are hoping anglers and others wading around Maryland rivers will consider sterilizing their equipment whenever they move from river to river, McKnight said.

“Every angler is not leaving litter behind and paying attention to the river and being advocates for it. They also need to start practicing some basic biosecurity,” he said.

smichael@baltimoreexaminer.com