Slime smothers streams in West - ecosystems threatened - Dydymosphenia geminata
- Slime smothers streams in West, threatening ecosystems - Didymosphenia
11/01/2005 01:00:00 AM
Slime smothers streams
Researchers are concerned about "didymo," pesky algae making their way
into waterways across the West, threatening ecosystems.
By Kim McGuire
Denver Post Staff Writer
[foto] Sarah Spaulding, a U.S. Geological Survey researcher, collects a
sample of didymo from a rock in Middle St. Vrain Creek near Nederland.
She says conditions are ripe for making the nuisance plant "one fat,
happy organism." (Post / John Epperson)
The brown slime blanketing the rocks in Middle St. Vrain Creek looks - to
the casual observer - like, well, slime.
But to biologist Sarah Spaulding, the algae, officially Didymosphenia
geminata, look like big trouble.
"Didymo," a.k.a. "rock snot," is spreading to streams across the country,
growing so thick it forms mats that look like toilet paper.
"Many of the people who see didymo actually think someone has dumped raw
sewage into the river," said Spaulding, a U.S. Geological Survey
"And that's never the case, as didymo usually occurs in what we think of
as clean waters," Spaulding said.
Didymo has been found smothering the bottoms of streams in the Western
states, including Colorado, Utah, Arizona and Nevada.
It is the prime suspect in the decline of brown trout in South Dakota,
where biologists think the organism has grown so thick it's choking out
the flies the fish feed upon.
"We think every angler out there should be paying attention to this one,"
said Kajsa Stromberg, conservation coordinator for the Federation of Fly
The rise of didymo is a mystery.
Species such as kudzu in the South and zebra mussels in the Great Lakes
have spread and become pests because they are exotics brought into the
United States from abroad.
But didymo has probably always lived in the high mountain, pristine lakes
of the West. In Colorado, it was first described in the Fryingpan River in
Didymo is microscopic diatom, a once rare organism with cell walls made of
silica, giving it a rough feel despite its slimy appearance.
In recent years, something has triggered the diatom to explode in numbers
and in places beyond its historical range, such as Arkansas and Tennessee.
"Clearly, conditions are stacking up somehow to make this one fat, happy
organism," Spaulding said.
"At first, I thought there had been some kind of mutation, but that's not
the case," she said.
Its discovery last year in New Zealand created a panic, leading the
government to restrict access at some rivers and to consider dousing
the algae in bleach or draining waterways.
In Colorado, there have been didymo blooms at about 40 sites, including
Boulder Creek, the east fork of the Eagle River and Bowen Gulch in Rocky
Mountain National Park.
The organism floats through a waterway and attaches itself to a rock by a
stalk. It forms a thick, brown mat - which smothers rocks, submerged
plants and other materials - and then breaks off and moves downstream.
Scientists suspect people - probably fishermen - play a role in spreading
the tiny plant.
In Montana, where didymo has been found in the Kootenai River,
conservation groups are trying to educate anglers on how to identify the
organism and how to avoid
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"Clearly there's a lot at stake when it shows up in a popular fishery,"
Travis Schmidt, a Colorado State University graduate student, is
collecting data on how didymo is affecting aquatic life in the state.
The preliminary results seem to show didymo edging out stone flies and
caddis flies, essential food for fish, Schmidt said.
Spaulding also hopes to collect enough data to determine how many Western
stream miles are covered by didymo.
"People generally don't care much about algae," she said. "But this is a
case where they probably should."
Staff writer Kim McGuire can be reached at 303-820-1240 or
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