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Rock Snot

Common Name
Rock snot or Didymo

Scientific Name
Didymosphenia geminata (Lyngbye) M. Schmidt

Status
Not yet found in Cape Breton
 

Description
  • Large single-celled diatoms (species of algae) 
  • Form massive blooms attaching to aquatic plants or submerged rocks
  • Color ranges from white to pale yellow-brown (rock snot is not green)
  • Has the texture of wet cotton or wool
  • Attaches via stalks, which is the majority of the visible portion
  • Individual cells are not visible until colonies form
  • The microscopic, single cells are shaped like ‘a curved bottle’
  • Compared with similar-looking algal species, rock snot has no distinctive odor when live
 


Habitat
Rock snot is a freshwater diatom and can be found in lakes, rivers, and streams.  Unlike most types of algae, rock snot prefers clear, cold, pristine waters which are oligotrophic (low in nutrients).  The depths at which rock snot can usually be found are between 10 cm to 2m.  In ideal conditions rock snot can multiply rapidly and form large mats encompassing most of the substrate or benthic zone in a body of water.
 
Invasion History
Rock snot has historically been found in the cool, oligotrophic waters of northern North America and northern Europe. According to citations provided through  the Global Invasive Species Database, rock snot is assumed to be indigenous (native) in Norway, Scotland, Ireland, Sweden, Finland, France, Spain, Switzerland and Vancouver Island, and in other Northern Hemisphere boreal or montane regions. Since the mid-1980s, it has begun to take on the characteristics of an invasive species within its original geographic range, and is being found in new areas such as western USA (New Hampshire, Vermont), mainland British Columbia, United Kingdom, and New Zealand.  
 
Regional Sightings
Mild or non-invasive versions of rock snot were geographically widespread and usually found in small isolated mountain populations within streams of western Canada.  After taking on the traits of an invasive species, rock snot has extended its range and habitat use in Canada. In 2006, this diatom turned up in Matapedia River in Gaspé, Quebec, Canada.  New Brunswick scientists now consider their rivers at high risk to a rock snot introduction and an invasion as now matter of time (click here for a CBC news article about rock snot threatening New Brunswick rivers). During the summer of 2007, the first population of rock snot was found in the Connecticut River in Pittsburgh, New Hampshire (click here for a NPR news article about rock snot in eastern U.S.A.).
 

Potential Impacts
The impacts of rock snot is not only considered to be a nuisance but can alter the whole ecosystem of a stream, river or lake. Rock snot may reduce the habitats of fish, aquatic invertebrates, and inhibit the growth of other diatoms.  Many species of fish, such as brook trout (Salvelinus fontinalis), prefer clean cobble streams and rivers which are at risk for being covered by rock snot mats.  Stream invertebrates tend to also reside in the cobble of stream beds and emerge to graze on algae.  Rock snot will not only inhibit native algae species but cover the area in which the invertebrates live.  In South Dakota, U.S.A., rock snot has adversely affected the brown trout fishery to the point of near collapse. It is suspected that environmental changes or perhaps genetic changes in rock snot have caused it to become invasive.

 
Special concerns for rock snot on Cape Breton Island
Rock snot is likely dispersed to new areas via contaminated footwear, fishing gear, and boats or trailers. It may only take one cell to start a new colony and result in the invasion of a new area previously uninhabited by rock snot.  In some cases in areas where rock snot has already been found (e.g. New Hampshire and Vermont) an algaecide, copper chelate, has been known to limit the growth of rock snot populations.  However, as with most invasive species, preventing the introduction in the first place is the best way to manage rock snot. Please be on the lookout for this aggressive invasive species.


Jennifer McKinnon photographed this sign while on a trip to Waitsfield, Vermont - thanks for the photo, Jennifer!
 

 

 
Additional web sites related to rock snot  
 
 
If you think you have spotted rock snot in a stream, pond or lake on Cape Breton Island, please contact us at: info@ProjectUFO.ca
 

 

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