Scientist say there's more to learn about didymo, or rock snot

 By John Hayes / Pittsburgh Post-Gazette

The didymosphenia geminata algae, or rock snot, that arrived in southwestern Pennsylvania last summer on the Youghiogheny River at Ohiopyle is icky and ugly, but it's uncertain how it will impact insect life and fish. At at Post-Gazette seminar Feb. 15 at the Allegheny Sport, Travel and Outdoors Show in Monroeville, Maryland Department of Natural Resources aquatic biologist Ron Klauda said that despite the invasive weed's 10-year presence in American fishing waters, there has not been a comprehensive scientific study of its impact on indigenous aquatic life.

"The mats get down in the rocks, but we don't know really how it effects benthic life [bottom dwelling plants and animals]," said Klauda, during a public interview at the Monroeville Convention Center. "We know that it's unusual in that the blooms are thickest in the early spring and fall -- not in the middle of summer like other aquatic weed growth -- and it doesn't grow uniformly. Some years it's worse than others, but we don't really know why."

Didymo is a nuisance, but is not toxic to humans. Klauda said blooms can grow from a single microscopic cell that can be transported in felt soles (legal in Pennsylvania), shoelaces, fish nets, ropes, boat hulls and just about anything. Anglers and boaters can help to slow the spread of didymo by cleaning boat hulls and wading boots on exiting the water. Diluted bleach or a saltwater solution will kill it but may corrode equipment.

"When I get home from wading, I put my boots in a laundry tub with warm soapy water," said Klauda. "By the time I'm done unloading the car, any invasive in there is dead.