Didymosphenia geminata (Lyngb.) M. Schmidt (ITIS)
Gomphonema geminata (Lyngb.) C. Agardh (ITIS)
Didymo, Rock snot
Northern Europe and northern North America (Spaulding and Elwell 2007)
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)
Exact pathway unknown, but it spreads easily through contaminated fishing gear, particularly felt-soled waders (Kilroy and Unwin 2011)
Alters stream ecology by forming dense algal blooms that can cover up to 100 percent of stream bottoms (Spaulding and Elwell 2007)
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.
Google. YouTube; Montana Fish, Wildlife, and Parks.
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
New York Invasive Species Clearinghouse.
DOC. NOAA. Great Lakes Environmental Research Laboratory; DOI. USGS. Wetland and Aquatic Research Center.
DOI. National Park Service.
See also: Environmental Factors - Invasive Species for more information
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.
University of California - Riverside. Center for Invasive Species Research.
Michigan State University Extension.
- Bergey, E.A., J.T. Cooper, and C.R. Tackett. 2009. Occurrence of the invasive diatom Didymosphenia geminata in southeast Oklahoma. Publications of the Oklahoma Biological Survey, 2nd Series 9:13-15.
Integrated Taxonomic Information System. Didymosphenia geminata. [Accessed Sep 10, 2014].
Kilroy, C. and M. Unwin. 2011. The arrival and spread of the bloom-forming, freshwater diatom, Didymosphenia geminata, in New Zealand. Aquatic Invasions 6(3):249-262.
Spaulding, S.A. and L. Elwell. 2007. Increase in nuisance blooms and geographic expansion of the freshwater diatom Didymosphenia geminata (PDF | 1.08 MB) (Open-File Report 2007-1425) Reston, Va.: U.S. Geological Survey.