Didymosphenia geminata, commonly known as didymo or rock snot, is a species of diatom that produces nuisance growths in freshwater rivers and streams with consistently cold water temperatures and low nutrient levels. [1]

Didymo (Didymosphenia geminata) is a type of invasive algae that attaches to plants, rocks, and other hard substrates in rivers and streams. Also called “rock snot” due to its slimy appearance, Didymo can produce thick mats that cover stream beds—making swimming, fishing, and other water activities undesirable.

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.

The Situation: Didymo or rock snot, is a highly invasive species of freshwater diatom that can form large and extensive mats in rivers, streams, and lakes. Didymo is native to cool temperate areas of the northern Hemisphere including Europe, North America, and Asia.

Didymo (also known as "rock snot") is a microscopic algae (diatom) that produces stalks that form thick mats on hard surfaces like rocks in stream beds. It looks and feels like white or tan/brown wet wool.

May 8, 2014 · A type of freshwater algae, known as "rock snot," that infiltrates river bottoms and clumps on rocks is not an invasive species introduced into waterways by humans, a new study finds.

Jan 7, 2020 · Didymo (Didymosphenia geminata) or "rock snot" is an invasive single-celled algae species that smothers stream and riverbeds with mats of algae up to 8 inches thick. Historically, the range of Didymo was in the northern edges of North America, Europe and Asia, and considered very rare.

Didymosphenia geminata is known by the common name, 'didymo'. It attaches by a mucopolysaccaride stalk to benthic substrates in flowing waters and splash zones of lakes. In some rivers, cells of D. geminata produce large amounts of stalk, so large that river bottoms may become covered by a thick felt.

Extracellular stalks that form nuisance blooms are secreted from the raphe (Spaulding and Elwell 2007). While microscopic, Didymosphenia geminata forms dense mats of extracellular stalks that are pale yellowish brown to white in color.

Didymosphenia geminata has the texture of wet wool or cotton, fibrous not slimy or slippery and is not easy to pull apart. It can reproduce asexually, resulting in large mats. It is able to spread from a single drop of water containing the diatoms.