What is Didymo?

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Nice article. An absolute "go to" fly throughout the year. Don't forget the scud on the steelhead tribs. Caught 2 this weekend on scuds!
 
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DaveKile
Didymo (Didymosphenia geminata) or rock snot is a non-native invasive microscopic algae that blooms in freshwater rivers and streams, with consistently cold water temperatures. Didymo forms a think brown mat of algae that can take over significant sections of stream.

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Didymo can be brown, tan or whitish in color covering vast stretches with it's wet cotton or steel wool feeling algae. It is not green or slimy.

Rock snot can take it's toll when it begins it's heavy blooms and smothers the bottom stream bed. It can choke out much of the aquatic life and can greatly impact the food supplies for trout in the ecosystem.

All states in the region have been impacted by this invasion species on some of the better known waterways including the East and West branches of the Delaware River, the Batten Kill and recently Pine Creek in Pennsylvania. The Pine Creek waterway does not show signs of these blooms as of yet. In Maryland, biologists first confirmed didymo in Gunpowder Falls in Baltimore County in early 2008. In 2009, it turned up in the lower Savage River, Allegany County and in Big Hunting Creek in 2012.

Jason du Pont produced and excellent video Didymo: A Video Diary on the transformation of the Gunpowder once a didymo bloom begins and takes over a stream.

The Pennsylvania Fish and Boat Commision offers these ideas to help control the spread of didymo:
"The PFBC recommends that anglers allow exposed equipment to completely dry before entering new waters. After equipment is dry to the touch, allow it to dry another 48 hours, the commission suggests. Thick and dense material, such as life jackets and felt-soled wading gear, will hold moisture longer, take longer to dry, and can be more difficult to clean.

Soaking equipment in hot water containing dishwashing detergent (two cups of detergent for every two and a half gallons of water) for 20 minutes or more also will kill didymo and some other aquatic invasive species.

Cleaning boats and equipment with hot water (maintained at 140 degrees Fahrenheit) by pressure washing or soaking is another effective method. If hot water is not available, a commercial hot water car wash also makes a good location to wash boats, motors and trailers. At the other end of the temperature range, freezing items solid for at least 24 hours is effective. If cleaning, drying or freezing is not practical, please restrict the equipment’s use to a single waterway."


For more details on how to stop the spread of didymo visit the PFBC page here.

While Didymosphenia geminata does not pose a health risks to humans, but it certainly causes significant issues for the aquatic life in our streams. Our attentiveness to this issue is the one way we can help stop the spread of this growing problem.

top photo - Tim Daley, PA DEP
 
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