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The Valley Reporter
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"Didymo" -- an invasive algae that chokes out the ecosystem



By Lizzy Hewitt, intern

Wet toilet paper, wet wool, and perhaps, most vividly, snot: All three are common descriptions of the invasive algae, <MI>Didymosphenia geminata.<D> Commonly known as didymo or rock snot, all it takes is a single organism to infest a river with this lumpy, brown slop. It suffocates the life out of the river; the entire food chain collapses. There are no fish left for fishermen, there's no clear water for swimmers and boaters. It has no known enemy or pest. There are no recorded cases of didymo ever being successfully removed from a river.


Native to Northern Europe and Canada, rock snot is famous for infesting clean rivers. New Zealand has been very affected by it. However, it became a reality for river-users in New England when it was discovered in the upper Connecticut River. It is now confirmed to be in the White River as well. Since it is so close, didymo has become immediate threat to the Mad River.

Didymo's aggressive nature has drawn comparisons to other invasive aquatic plants that have entered the area. Said Jack Byrne, Moretown resident and longtime member of the Friends of the Mad River, "Just like we are seeing Japanese knot weed spreading up all over our riverbanks and pushing out native plants.  Didymo has the potential to do the same thing to the river itself. It could drastically change what could live in the river; change it so that there will be fewer trout and much less diversity among critters."


Before leaving a river's edge, look

for clumps of algae and sediment,

and remove them. Leave them at

the site.


Soak all gear for at least one

minute in a two percent (by volume)

solution of household bleach,

or a five percent (by volume) solution of

dishwashing detergent or salt.

All surfaces must be in contact

with the cleaning solution for

a full minute. Water-absorbent

equipment (lifejackets, waders)

should be soaked thoroughly to

ensure complete contact.


If cleaning is not practical, after

the item is dry to the touch, leave

it to dry for at least another 48

hours before using in another

freshwater system.

Information courtesy of U.S. EPA.


Barry Bender of Clearwater Sports is also concerned based on his observations on other invasive species.  "I'm reminded of when Malaysian milfoil was on Lake Champlain, it gets caught on propellers and spreads the seeds. I've watched entire shorelines get choked out by this stuff. [Didymo] is worse. It kills the fish habitat. It basically chokes out the ecosystem."

Clark Amadon, president of the Mad Dog chapter of Trout Unlimited, is focusing his energy on raising public awareness about the algae. "The most significant efforts right now are educational efforts: putting up posters, news, radio, TV. Ultimately, we want to be able to approach any river user and have them know all about didymo."

Amadon's goal for universal understanding of rock snot may be ambitious, but it's necessary in the fight to keep it out of the Mad River. "The only way it spreads between watersheds is by people.... Our goal is to keep it clear and clean and to go out of our way to clean our gear before we go in."


"It's not only boating but also fishing that has the potential to spread it," says Bender. "People using felt shoes and walking on rocks. Out-of-staters and people who don't know about it. They have the greatest potential to spread it."

Every time anybody uses their equipment in different rivers it should be cleaned. This includes canoes, kayaks, paddles, fishing equipment, lifejackets, water shoes and tubes. Posters with information on how to clean equipment are turning up in the community. One is already up at Clearwater Sports.

"I think those people who depend on the river for their business should take part in making everybody aware of the threat by making information available for their customers," says Byrne.

Clearwater Sports is already working to prevent didymo from entering the watershed. "We've been talking it up, informing our guides, personnel and customers about it," reports Bender. "If we're aware that the gear has been taken to those rivers with didymo in it we quarantine those boats. We don't want to see it in the Mad River."

The presence of didymo in Vermont rivers means that river users all over the state will have to put more time into cleaning their equipment. Byrne is quick to remind how heavily the community relies on the health of the watershed. "If it ever took root as it has in other places it would turn the river into an undesirable place. It would make it very unpleasant to wade or swim; make it unpleasant to look at. We would have to spend a lot of time, effort and resources to figure out how to control it. That obviously could affect the tourist trade here. A lot of people come here for the river and if they found it wasn't a desirable place anymore they might look elsewhere."

Bender has never seen it in person, although he is sufficiently convinced by pictures he has seen of it. "It looks like a white, brown, gray blob. It's gooey and it sticks to things."

So far didymo has not been detected in the Mad River watershed. "If somebody finds it, I think they should contact the Agency of Natural Resources," says Byrne. "Keep a sample of it, put it in a bottle or jar so they can show somebody who's an expert. Keep a record of where they found it."

Amadon remains optimistic. "There is some relatively good news. Hopefully we found it early enough to prevent it from spreading much more."

"Let's make this a group effort," says Bender, "a community effort to question and harass friends we know have been using other rivers to clean their equipment."

"I think the best people can do is to be aware of it, look out for it, and don't laugh about it. If you see some, inform others of its location," says Bender.

On September 8, posters will be put up at main access areas throughout the watershed. For more information on didymo, or on how to get involved, visit www.friendsofthemadriver.org.


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