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Didymo

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Rock snot (didymo)
Rock snot (didymo) - Photo by T. Thorney
Scientific Name: 

Didymosphenia geminata (Lyngb.) M. Schmidt (ITIS)

Synonym: 

Gomphonema geminata (Lyngb.) C. Agardh (ITIS)

Common Name: 

Didymo, Rock snot

Native To: 

Northern Europe and northern North America (Spaulding and Elwell 2007)

Date of U.S. Introduction: 

Was present in Canada in the late 1800s, but did not begin to cause problems until the early 1990s. It was first discovered east of the Mississippi River in 2005 in Tennessee. (Bergey et al. 2009; Spaulding and Elwell 2007)

Means of Introduction: 

Exact pathway unknown, but it spreads easily through contaminated fishing gear, particularly felt-soled waders (Kilroy and Unwin 2011)

Impact: 

Alters stream ecology by forming dense algal blooms that can cover up to 100 percent of stream bottoms (Spaulding and Elwell 2007)

Current U.S. Distribution: 
Scattered populations exist throughout the United States, including New England, the Mid-Atlantic Region, and the Western U.S.

Spotlights

Michigan Department of Natural Resources.

The Michigan departments of Environment, Great Lakes, and Energy and Natural Resources confirmed a report of didymo, a nuisance freshwater alga, in a stretch of the Upper Manistee River in Kalkaska County. Also known as rock snot despite its coarse, woolly texture, didymo can grow into thick mats that cover the river bottom. The Manistee River finding marks the first detection of didymo blooms in the Lower Peninsula. In 2015, extensive mats of didymo were found on the Michigan side of the St. Marys River near Sault Ste. Marie in the Upper Peninsula.

If you observe didymo in the water, either as small, cotton ball-sized patches or thick blankets with rope-like strings that flow in currents, take photos, note the location and report it by using the Midwest Invasive Species Information Network, available online at MISIN.MSU.edu or as a downloadable smartphone app. The MISIN smartphone app will take a GPS location point if a report is made at the site; it also will allow you to upload photos with a report. Find more information on didymo and how to identify it at Michigan.gov/Invasives.

Images

Videos

Google. YouTube; Montana Fish, Wildlife, and Parks.

Selected Resources

The section below contains highly relevant resources for this species, organized by source. Or, to display all related content view all resources for Didymo.

Council or Task Force

Alberta Invasive Species Council (Canada).

See also: Fact Sheets for more information about individual invasive species, including those listed as "Prohibited Noxious" and "Noxious" under the Alberta Weed Control Act

Partnership
IUCN. Species Survival Commission. Invasive Species Specialist Group.
Northeast Aquatic Nuisance Species Panel.

New York Invasive Species Clearinghouse.

Federal Government

DOCNOAA. Great Lakes Environmental Research Laboratory; DOIUSGS. Wetland and Aquatic Research Center.

International Government

Otago Regional Council (New Zealand).

State and Local Government

Rhode Island Department of Environmental Management. Office of Water Resources.

See also: Aquatic Invasive Plants for species of concern

Pennsylvania Fish and Boat Commission.

See also: Aquatic Invasive Species for more action plans

New York Department of Environmental Conservation.

Virginia Department of Wildlife Resources.

Pennsylvania Department of Conservation and Natural Resources.

See also: Invasive Plant Fact Sheets for plant species (trees, shrubs, vines, herbs and aquatic plants) that have impacted the state's natural lands

Missouri Department of Conservation.

See also: Don't Spread Didymo for more information

Maryland Department of Natural Resources.

Academic

University of California - Riverside. Center for Invasive Species Research.

Pennsylvania State University. Pennsylvania Sea Grant.
See also: Aquatic Invasive Species: Resources for additional species information

Michigan State University Extension.

Citations