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Waitsfield, VT 05673

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Didymo confirmed in the Mad River



By Lizzy Hewitt, contributing reporter

The invasive algae didymosphenia geminata, or "rock snot," was confirmed in the Mad River by the Vermont Agency of Natural Resources last week. It has been found between the Warren Park-and-Ride and the Lareau Swimming Hole in Waitsfield.

Didymo was first sited in Vermont in the Battenkill River in 2006. In 2007, it was confirmed to be present in the White River and the Connecticut River. The sighting in the Mad River is the first in the Lake Champlain Basin.

It's difficult to identify how didymo spreads. Caitrin Noel, watershed coordinator for the Friends of the Mad River, said there is no clear culprit that brought it to the system. "It's possible that it was brought in by users of the stream: swimmers, animals, birds even, dogs, fishers, boarders, tubers."

Little is known about how didymo will affect the watershed, although there is no evidence that suggests that it is harmful to the health of humans or pets. 


"It has the potential to alter the insect and native algae populations. The base of the food chain definitely has the potential to be changed. These mats can reduce or even exclude native populations," Noel said.

Besides the implications for the health of the river, it's aesthetically unpleasing and pervasive. There are no instances of didymo being successfully eradicated from a river once it has entered the water system.

Didymo is easy to identify. It grows in extensive mats over a rocky riverbed, with plenty of exposure to sunlight. The lumpy brown appearance inspired the nickname "rock snot." The texture is similar to cotton or wet wool.

Nobody is sure how didymo will behave in this habitat. Its presence in the Mad River presents an opportunity to study how it impacts native species.

"There is some existing data on what the macroinvertabrate population was in the past, so we can use that to compare how didymo affects these populations," Noel explained.

The existing Mad River Watch program, which monitors 30 sites along the river for <MI>E. coli<D> throughout the summer, will serve as an excellent resource for that research and Friends of the Mad River is also looking to partner with another institution or college for research purposes.

Didymo has already been seen to vary greatly within a single season. Noel remarked that Dr. Leslie Matthews of the Agency of Natural Resources, who has been tracking didymo's progress through Vermont, noticed a cyclical pattern in the blooms in the White River last summer. "It can come and go quickly. We're really not sure how quickly it can bloom or how quickly it goes away."

The best way to keep didymo from spreading further is widespread education of healthy river practices. According to researchers, the discovery of didymo so far upstream in the Champlain Basin is unfortunate because little can be done to prevent it from moving downstream.  

"Now that we know there's didymo in the Mad River, it's essential that people think about that and not bring it over to other rivers in the state," explains Noel. "If you're moving from water body to water body it's really important to clean all your equipment to prevent hitchhiking."  


The ANR suggests washing all equipment in warm soapy water or bleach. This will help not only to prevent the spread of didymo, but also other invasive species and threats to healthy rivers, such as viral hemorrhagic septicemia, a fish disease.

Additionally, river users can help to track where didymo is present throughout the water system. "I want people to ask us about how to identify didymo. If people do find it in very upstream areas and tributaries, it would be great if they could report it to us," said Noel, noting that she will be posting more information on the Friends of the Mad River website as it becomes available.

Noel stresses that this isn't an obituary for the Mad River. "It's still going to be a beautiful river; we just have to be careful about how we use our equipment. There's a lot we don't know, and I think when people see the worst case scenario photos from New Zealand they get really scared. But it hasn't been like that in Vermont so far."
Friends of the Mad River, Trout Unlimited, and other local organizations are planning to meet this week to collectively work on a strategy for outreach regarding didymo. Noel encourages people to contact Friends of the Mad River for further information and to report sightings.


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