Maryland's premier trout stream, Gunpowder Falls, is under attack from an algae strain feared worldwide for its ability to coat the bottom of rivers and lakes and smother the habitat and food supply of fish.
Heavy, with the consistency of a wool coat, Didymosphenia geminata is a recent invader of East Coast waterways. It begins as microscopic organism that travels from stream to stream on boats, fishing gear and the bottoms of felt boots and waders.
The algae is not hazardous to humans, but could have a "profound" effect on fish and the quality of freshwater streams and recreation, upsetting the delicate balance of nature, said Jonathan McKnight, coordinator of the Department of Natural Resources invasive species team.
It seems to favor running water below dams. The largest concentration to date is where the Gunpowder crosses Falls Road, where it covers 20 percent of the river bottom.
"We don't have a scientific smoking gun on this thing. This is brand new here. We don't know what it's going to do," McKnight said. "But intuitively you can't have something cover 25 to 50 percent of your stream bed without it having an effect."
Discovery of algae, which scientists call "didymo" or "rock snot," has come at the height of trout season, when waters around the state have been stocked with hundreds of thousands of fish and anglers hopscotch from prime spot to prime spot. It takes a single cell to contaminate a stream.
"We are our own worst enemy," McKnight said. "We're moving this stuff around."
Theaux LeGardeur, owner of Backwater Angler, a fly-fishing shop in Monkton not far from the river, said unlike a decade ago, "everyone is traveling to fish. We have customers who hit the Delaware River and then come here. They can definitely bring it from the Delaware, from the Battenkill River [in Vermont]. I've certainly written a number of licenses for customers from Tennessee and North Carolina, where didymo has been detected."
Of greater concern to scientists and the nearly 66,000 anglers who buy Maryland trout licenses is that didymo could be carried from the Gunpowder, nationally recognized as a Blue Ribbon Trout Stream, to the state's other heralded fishing spots. Kayakers and canoers who paddle multiple waterways increase the risk.
"How hard is it going to be to jump to the Casselman, the Savage River, the North Branch of the Potomac and Big Hunting Creek?" said McKnight, naming trout waters farther west. "We're talking about the who's who of great trout waters."
