Synonyms: Rock Snot.
Didymo is an invasive species in Maryland (MISC 2022). Didymosphenia geminata is native to northern Europe and North America and did not seem to present an ecological problem until the latter part of the 20th century. In recent years, it has migrated farther south and is now considered invasive in many countries including some in the Southern Hemisphere. Under certain conditions, Didymo can produce macroscopic gelatinous colonies that cover rocks in streams. Didymo is thought to be spread by humans, particularly by fisherman wearing soft-textured waders. Visitors to Maryland State Parks may have seen wader-scrubbing stations intended to reduce the spread of Didymo from one stream to another. Felt-bottom waders are now prohibited in Maryland waters.
Didymo is a microscopic species and microscopy is necessary to confirm identification. Other species of diatoms and cyanobacteria will form brown mats, particularly in the colder months.
Didymo has been confirmed by the Maryland Department of Natural Resources to occur in Big Hunting Creek, Gunpowder River, North Branch of the Potomac River, and Savage River (MD DNR presentation).
There are 0 records in the project database.
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