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Didymosphenia geminata, commonly referred to as "didymo", is a freshwater microscopic diatom. It is found in streams and rivers in much of North America. Didymo increasingly poses a threat to aquatic ecosystems because it forms extensive mats on stream beds. Didymo attaches to the streambed by a stalk. These stalks have a rough texture similar to wet wool and mimic strands of toilet paper, as opposed to other algal species which feel "slimy".
Prevent the Spread:
Decontaminating equipment between uses in different freshwater systems is important to prevent the spread of didymo. Hard copies of the flyer available upon request.
Recommendations for Response:
Didymosphenia geminata is expanding its geographic range. Historically, this diatom occurred mostly in northern latitudes in low nutrient waters; now it occurs in more nutrient-rich water and at lower latitudes.
- White paper - January 2007 PDF (33 pp, 1.7 M, About PDF)
- Distribution map - Confirmed presence of D. geminata in the United States and Canada PDF (1 pp., 76 K, About PDF)
A rough field guide for identification of D. geminata PDF
(2 pp. 40K, About PDF)