Invasive algae put region on alert

STOCKBRIDGE, Vt. -- With steep banks, deep pools, and pebbly shores, this scenic stretch of the White River has long been a haven for fishing, swimming, and floating on inner tubes. But biologists fear that an invasive algae known as "rock snot" could drive away swimmers and fish.

"I think if it takes hold, if it forms these massive blooms, it will really change the face of White River as we know it," said Mary Russ, executive director of the White River Partnership.

The aquatic algae didymo -- Didymosphenia geminata -- has infested rivers in New Zealand with gray floating growth but had never been seen in the Northeast before this summer, when fishermen spotted it in the upper Connecticut and White rivers.

Northeast states are on alert, warning anglers and boaters to scour their boats and clean their gear to prevent the algae's spread.

"Please don't take chances, disinfect your fishing gear," said Scott Decker, program supervisor with the New Hampshire Fish and Game Department.

That is the only weapon against didymo, which is thought to have been spread by fishermen whose gear is absorbent, or by other recreational users. The algae can spread into thick mats with long stalks and have been described as resembling a sewage spill and having a woolly texture.

Didymo attaches to rocks in the river bottom, smothering habitat for insects, and in turn, removing a food source for fish.

"Once you remove [insects], young fish don't have anything to eat," said David Deen, a state representative, fishing guide, and river steward for the Connecticut River Watershed Council. "Growth is slowed at best and at worst they could starve to death."

The algae have preferred high-altitude, low-nutrient rivers but now are showing up in other places, raising questions about whether they have mutated and what triggers their growth.

New Zealand, Poland, Canada, and northwestern states have been battling didymo and now Arkansas and Tennessee have large populations.

Underhill fly fishing guide Lawton Weber, who first spotted the didymo on the Connecticut River in Bloomfield in June, said he knew it was spreading in the United States and that Vermont had the habitat for it.

"It took me two seconds to go, 'That's didymo,' " he said. "It scares me because, first of all, it's an aesthetic eyesore when it's in full-bloom mode, and its impact on the trout population is going to be significant."

The biggest concern is keeping it from spreading. But that's the challenge, since a single cell, invisible on clothing or gear, could infest a waterway.

On a steamy Sunday in July, North Pomfret fishing guide Brad Yoder estimated 150 inner tubes glided down the White River.

"You don't necessarily have to see it on the clothing or whatever because it's cellular," he said of the algae.

Anglers and anyone else using the rivers are asked to remove all visible clumps from their gear, clothing, shoes, and boats and to scrub boats and soak clothes, felt-soled waders, and other items in hot, soapy water for 30 minutes.

For now, the didymo is in its early stages, forming nubby brown growths on rocks. No one knows what it will do next.

"I think all of the Northeast is tuned in to see what the effects will be so they can start taking preventive measures," Russ said.