May 13, 2014 — Rock snot, a slimy-looking algae that vexes salmon and salmon fishermen, is not an alien invader but a homegrown threat gaining strength in changing water conditions, according to a new study by scientists from Dartmouth and Environment Canada.
Officially known as Didymosphenia geminata, which scientists shorten to didymo, it has existed in portions of Alaska for some eight centuries, said the study published online last week in the journal BioScience.
Only recently, though, has the nuisance algae been noticed, even in sites considered pristine, thanks to aggressive growth that spreads rock snot stalks in lakes, rivers and streams.
"It's in Patagonia. It's in Tierra del Fuego. It's in Alaska," said study co-author Brad Taylor of Dartmouth College. It is also in British Columbia, New York and various northeastern U.S. states. Sweden, Poland and Colorado see it, too.
Alaska officials have waged a crusade against rock snot. Alaska is among several states that ban felt soles in fishermen's waders; the state Department of Fish and Game cites felt's ability to absorb and transport a plethora of unwanted organisms to new places. The Alaska House this year passed a bill that allows state officials to mount a rapid response to eradicate invasive aquatic species and establishes a fund to pay for it; the bill died, however, without Senate action.
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But when it comes to combating rock snot in Alaska, anti-invader strategies may do little, according to Taylor's study. Core samples at Naknek Lake show that rock snot has been there since the year 1200, the study notes. As long as the didymo did not bloom, Taylor said, it went mostly unnoticed.
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