Rock snot

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Yicky, yucky rock snot… on this CurrentCast.

Rock snot (Didymosphenia geminata) is an algae that most anyone can identify, thanks to its snot-like appearance. Although it’s not toxic, rock snot can overgrow native algae that insects and fishes in the stream rely on for food. It can also smother the streambed, which in turn can affect the flow of water over fish eggs.

Rock Snot

Rock snot is spread from stream to stream on the soles of boots, the bottoms of canoes, or in the bilge of kayaks. Dave Arscott, Assistant Director of Stroud Water Research Center, says once it’s in the water there is no way to remove it, so prevention is key.

Arscott: “We need to clean, check and dry our gear as we move from waterway to waterway.”

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GBF: Presence in the Great Lakes
According to the Invasive Species Centre (June 2017), while rock snot is present in the Great Lakes, it has historically been limited to Lake Superior, but has recently been a problem in the St Mary’s River which connects Superior to Huron. GBF's David Sweetnam says this algae is not an alien invasive species in the Great Lakes, but in excess it can be problem.

The Canadian Food Inspection Agency did a Risk assessment on this species in 2009 which stated "All the evidence points to accidental introduction by people participating in recreational activities, such as boating and fishing, being the means by which Didymosphenia geminata has moved long distances outside of its native range", "There is no evidence that Didymosphenia geminata has ever been deliberately introduced into a waterway. At low population levels, the cells are invisible to the naked eye and at high population levels, during blooms, the algal masses are very unattractive, so they are very unlikely to be transported by water gardeners or other horticulturalists." The report goes on to say that if there is excessive production of this species, biodiversity can be reduced and altered in certain species, and people swimming in water below "Didymosphenia geminata blooms have complained of eye irritations, possibly due to the silica in the frustules". Part of conclusion from this report included "The exact distribution in Canada is still uncertain and will require further surveys to determine. However, it has proven to be invasive in North America and New Zealand and to negatively impact freshwater fish habitats in streams, so it might be desirable to minimize its spread within Canada even if it is not subject to regulation as a quarantine pest. " From "Weed Risk Assessment", Canadian Food Inspection Agency, Plant Health Risk Assessment Unit, Science Advice Division, Ottawa, Ontario, Aug. 4, 2009.

Listen to the podcast.

Environmental DNA (eDNA) can track rock snot and other difficult to detect species
Interesting article in The Scientist link.
At GBF, we are building a library of aquatic species, that can be used by scientists in the future to track existence of relative abundance of species. Click here to learn more.

Other ways to protect coastal wetlands

Georgian Bay Forever is working with communities and partners to help stop invasive Phragmites from taking over Georgian Bay's coastal wetlands. These plants grow into monocultures which threaten biodiversity and hurt wetland function. To find out more about invasive Phragmites and community Phragbusting, please read on.