Not knowing what’s going on with this new blooming is causing concern.
from the March 01, 2007 edition - http://www.csmonitor.com/2007/0301/p13s01-sten.html
Mysterious alga threatens rivers
'Didymo' is perplexing scientists as invasive, ruglike blooms of the stuff snarl waterways in both hemispheres.
By Moises Velasquez-Manoff | Correspondent of The Christian Science Monitor
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," says Max Bothwell, a 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.
Scientists warn that the blooms could spread throughout cold rivers in both hemispheres if not kept in check. Utility companies eye didymo nervously as a costly fouler of intake grates. Anglers and ecologists worry about its potential effects on a river's food web. Its major effect so far seems to be aesthetic – the algal mats are often compared to shag carpeting or fiberglass insulation. But the larger question keeps scientists musing: What could have led to such rampant blooms? In today's well-traveled world, suspicion fell squarely on humans. But inadvertent dispersal by globe-trotting citizens doesn't totally account for its rapid spread.
And how could it "invade" places where it already lives? These contradictions have led some to suggest an evolutionary event: an innocuous alga mutating into a superstrain.
