Didymosphenia geminata (Lyngb.) M. Schmidt (ITIS)
Didymo, Rock snot
Gomphonema geminata (Lyngb.) C. Agardh (ITIS)
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)
Scattered populations exist throughout the United States, including New England, the Mid-Atlantic Region, and the Western U.S.
Find more images
The section below contains highly relevant resources for this species, organized by source.
Council or Task Force
State and Local Government
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.