National Invasive Species Awareness Week — Didymo (Rock Snot)

Posted on: March 1st, 2018 by Samantha Kahl

Day 4 of National Inva­sive Species Aware­ness Week is ded­i­cated to Rock Snot!

What is it?

Didy­mos­pher­nia gem­i­nata a.k.a. Didymo a.k.a. Rock Snot, is an aquatic, inva­sive, micro­scopic diatoma­ceous algae that pro­duces high vol­umes of stalk mate­r­ial, which is why you may see thick mats on stream bot­toms. It is often brown, tan, or white, with the appear­ance and tex­ture of wet wool that does not fall apart easily.

Didymo in the Esopus Creek. photo courtesy of NYIS

Didymo in the Eso­pus Creek.
photo cour­tesy of NYIS

How does this impact streams?

Because Didymo grows on the bot­tom of streams and still waters, and forms thick mats of mate­r­ial, it can last for months, despite occur­ring through­out some fast mov­ing streams. When Didymo grows, or blooms, it cov­ers entire stream beds, cov­er­ing over native organ­isms, and restrict­ing the avail­abil­ity of food for native fish species. It spreads quickly and eas­ily due to water recre­ation activ­i­ties. Fish­ing, kayaking/canoeing, tub­ing, and boat­ing allows the micro­scopic algea to attach onto your boots, waders, and boats, and if not cleaned off prop­erly, it will spread to the next body of water you go to. Cur­rently, there are no con­trol meth­ods avail­able to stop the spread and erad­i­cate Didymo.

Make it stop!

NYS DEC urges the pub­lic to use the “Inspect, Clean and Dry” method to decrease the spread of inva­sive species. If for any rea­son you can’t get your equip­ment clean and dry, restrict your equip­ment to a sin­gle water body.

Density Observations of Rock Snot. map courtesy of NYIS

Den­sity Obser­va­tions of Rock Snot.
map cour­tesy of NYIS


**Atten­tion Felt-Sole Waders! We encour­age you to con­sider other alter­na­tives, such as rub­ber stud­ded boots. Because felt-soles absorb Didymo cells and remain absorbent for long peri­ods of time, the spread of Didymo can increase rapidly if spe­cial treat­ments are not conducted.

Check back tomor­row for our final day of National Inva­sive Species Aware­ness Week!

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