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You are here: Home / Aquatic Species / Species Profiles / Didymo
Aquatic Species
  
Species Profiles

Didymo

Didymo - USGS, FCSC

Scientific name: Didymosphenia geminata (Lyngb.) M. Schmidt (ITIS)

Synonym: Gomphonema geminata (Lyngb.) C. Agardh

Common names: Didymo, Rock snot

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Selected Resources

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; Schroeder 2005)

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.

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Partnership

Invasive Species Compendium - Didymosphenia geminata
CAB International.

New York Invasive Species Information - Rock Snot, Didymo
New York Invasive Species Clearinghouse.

Didymo (a.k.a. rock snot)
Northeast Aquatic Nuisance Species Panel
.

Global Invasive Species Database - Didymosphenia geminata (algae)
World Conservation Union. Invasive Species Specialist Group.

Government

Didymosphenia geminata, "Didymo" or "Rock Snot"
DOI. FWS. Connecticut River Coordinator's Office.

Invasive Species: Didymo a.k.a. "Rock Snot" (Apr 2010; PDF | 142 KB)
DOI. NPS. Yosemite National Park.

Didymosphenia geminata in British Columbia Streams
British Columbia Ministry of Environment (Canada).

Didymo
Environment Bay of Plenty Regional Council (New Zealand).

Didymo
New Zealand Ministry of Agriculture and Forestry. Biosecurity New Zealand.

Didymo
Otago Regional Council (New Zealand).

State

New Aquatic Nuisance Species Threatens Maine streams and Rivers: Didymo or "Rock Snot"
Maine Department of Environmental Protection. Bureau of Land and Water Quality.

Didymo Alert
New York Department of Environmental Conservation.

Invasive Plants in Pennsylvania: Didymo (PDF | 153 KB)
Pennsylvania Department of Conservation and Natural Resources.

Do you know about Didymo?
Pennsylvania Fish and Boat Commission.

Didymo or Rock Snot (Didymosphenia geminata) in Vermont and the Northeast
Vermont Agency of Natural Resources. Department of Environmental Conservation. Water Quality Division.

Didymo (Invasive Freshwater Algae) in Virginia
Virginia Department of Game and Inland Fisheries.

Didymo (Rock Snot) Fact Sheet
West Virginia Department of Natural Resources.

Academic

Didymo (or Rock Snot)
University of California, Riverside. Center for Invasive Species Research.

How Didymo Became Rock Snot (Dec 2009)
University of Minnesota. Minnesota Sea Grant. Seiche Newsletter.

Didymo: Didymosphenia geminata (PDF | 211 KB)
Pennsylvania Sea Grant.

Professional

Citations

Bergey, E.A., J.T. Cooper, and C.R. Tackett. 2009. Occurrence of the invasive diatom Didymosphenia geminata in southeast Oklahoma (PDF | 79 KB) 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.

Schroeder, O. 2005. Invasive algae 'Didymo' found in Tennessee River. Tennessee Wildlife Resources Agency.

Spaulding, S.A. and L. Elwell. 2007. Increase in nuisance blooms and geographic expansion of the freshwater diatom Didymosphenia geminata (PDF | 1.08 MB) U.S. Geological Survey. Open-File Report 2007-1425.

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Last Modified: Apr 17, 2015
 
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