|Didymo - MDC|
Rock snot is also called Didymo, short for Didymosphenia geminata. It is an algae whose infamy comes from its ability to rapidly proliferate and cover the bottoms of streams in dense mats, choking out the normal macroinvertebrates which are important links in the food chain for the fish we love to catch. In addition, it forms dense slimy sheets which cling to waders and fishing lines, eventually making fishing and swimming unpleasant or even impossible.
"Didymosphenia geminata is a diatom, which is a type of single-celled algae unique for their silica (SiO2) cell walls. The life history of diatoms includes both vegetative and sexual reproduction, though the sexual stage is not yet documented in this species.
The stalk can attach to rocks, plants, or other submerged surfaces. When the diatom cell divides, through vegetative reproduction, the stalk divides too, eventually forming a mass of branching stalks. The nuisance build-up is not the cell itself, but their massive production of extracellular stalks." *
While invasive species are frequently defined as non-natives or exotics (i.e. brought in from other regions), Didymo is a native to the Northern Hemispheres of both Asia, Europe and America. Over the last 20 years it has been proliferating in its native range as well as slowly expanding into other waters. It first appeared in New Zealand in 2004 and its spread there is documented in Wikipedia.
Once in the water, it is impossible to eliminate. Prevention is focused on preventing the spread of the moist diatoms from one watershed to another. Felt soled waders and moist boats and containers are the mechanism of spread and the article defines steps to avoid spreading the algae. The steps of Check - Clean - Dry are outlined in today's News-Leader article on Didymo.
At last Rock Snot is getting the disrespect it deserves.
* The science of Didymo is in this Wikipedia article.