Another premier Maryland trout stream has become tainted by an invasive algae feared worldwide for its ability to coat the bottom of rivers and lakes and smother the habitat and food supply of fish.
Biologists at the Department of Natural Resources announced Wednesday that didymo, known by anglers as "rock snot," was found in Garrett County's Savage River late last month.
"There's nothing we can do short of closing the area down, and that's draconian," said Don Cosden, inland fisheries director. "We're going to try hard to contain it."
Officials fear the algae could spread to the North Branch of the Potomac below the Jennings Randolph Reservoir, another of the state's best trout waters.
Didymosphenia geminata is a recent invader of East Coast waterways that hitchhikes from stream to stream on boats, fishing gear and the bottoms of felt boots and waders. The algae is not harmful to humans, but it is nearly impossible to eradicate once it takes hold.
The matlike algae was first detected in Maryland last year in Gunpowder Falls, just below Prettyboy Reservoir. DNR's invasive species team built and distributed washing stations at popular spots along the river and other fishing sites so that anglers could clean their waders and gear of any bits of algae.
"Someone who fishes the Gunpowder is likely to fish the Savage or Big Hunting Creek," Cosden said. "That's been the pattern. The better trout streams is where it's showing up."
Cosden said biologists doing routine water-quality testing just below Savage River Dam were suspicious of initial results and went back to test again. This time, they found a small mass near a footbridge and on some rocks.
Didymo was first identified in the 1890s in Europe and China. Scientists on the West Coast detected it a decade ago. An outbreak in New Zealand in 2004 prompted a "biosecurity lockdown," with checkpoints and penalties of five years in prison and $100,000 fines for anglers and boaters who failed to clean their gear. A year later, reports were down 90 percent, but officials warned the decrease could be part of a natural cycle.
The same thing could happen here, Cosden said. Didymo "doesn't compete well" in rivers where other algae is present, a condition that exists in the Gunpowder and the Savage rivers. But the North Branch, with its ice-cold water and clean bottom, is a perfect host for didymo, he said.