Public asked to help prevent spread of invasive algae  

Jun. 26, 2007

By Dave Treadway
Nashville District

The Tennessee Chapter of Trout Unlimited with the aid of Tennessee Wildlife Resources Agency is erecting signs along state waterways to help people identify an invasive alga called didymo and provide instruction about how they can help the state fight it.

The Kentucky Department of Fish and Wildlife Service also likes the signage and may, with assistance from the U.S. Fish and Wildlife Service, adapt if for placement on Kentucky waterways.

In the late 1980s, a freshwater alga began mysteriously blooming in the rivers of Vancouver, British Columbia, covering once-pristine riverbeds with a thick, woolly mat.

Dubbed "rock snot" for its yellowish color and globular form, the sudden dominance by a previously benign alga presented something of a puzzle. Thought of as native to the area - and to many rivers and streams throughout the northern hemisphere - this particular alga was acting as if it had just been introduced.

"This is the mystery," said Max Bothwell, research scientist with Environment Canada who studied the Vancouver blooms. "How could an endemic species invade?"

Scientists, who often refer to Vancouver's experience as the "epicenter" of an ongoing global epidemic, are still not quite sure. Known as didymosphenia geminata, or "didymo" for short, the alga (algae is the plural form) has since bloomed in the Ozarks, the Rockies, Iceland and Eastern Europe. And its worldwide spread seems to be accelerating.

In 2002, didymo appeared in South Dakota, causing a near collapse of the Rapid Creek brown trout fishery. In 2004, it jumped hemispheres, covering New Zealand's famously scenic rivers with mats the likes of which scientists had seen nowhere else. And just last year, the alga appeared in Quebec's Matapedia River, an important East Coast salmon fishery.

The signs tell boaters to remove clumps of the algae and sediment from their gear before leaving the water's edge.

Boaters can clean gear by soaking it in a 5 percent solution of household bleach or dishwashing detergent for at least a minute.  Water-absorbent equipment should be soaked thoroughly to ensure complete contact.  If cleaning is not practical, leave the gear to dry for at least 48 hours before using it in another body of water.