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​​Protecting Northern Michigan's water resources since 1979.
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Rock Snot (Didymo)

Common Names: Rock Snot or Didymo

Scientific Name: Didymosphenia geminata

Identification: Rock Snot, also known as didymo, is a non-indigenous nuisance diatom. It can form large mats along the bottom of a river or stream, ranging in color from white to brown. The texture of these mats has been described as similar to cotton or wool. 
Picture
Credit: West Virginia Department of Natural Resources
Nuisance blooms of Didymo, like the one shown above, can smother river and stream bottoms altering the aquatic ecosystem and impeding recreational uses of a water body.
Picture
Credit: Tim Daley, Pennsylvania Department of Environmental Protection
Rock Snot is NOT SLIMY
Impacts of Rock Snot:
Didymo is "snot funny" and could be a potential aquatic invader in Northern Michigan’s rivers and streams. Didymo may be spread by transferring a single drop of water hosting the microscopic organism to unaffected water bodies possessing ecological conditions that are capable of supporting the species. It can be inadvertently transported in boats, fishing gear, and especially waders.

Didymo blooms can be a nuisance and impede recreational uses of a water body. The species is capable of creating thick mats that smother the rock and pebble based habitat critical for supporting fish populations and the macroinvertebrate communities, which are important components of Northern Michigan's stream ecosystems. 
What you can do to prevent the spread of this aquatic invasive species
  • Learn to identify Rock Snot (Didymo)
  • Don’t wear porous-soled waders when fishing in rivers and streams.
  • Consider replacing felt-soled waders with a new, environmentally sensitive alternative.
  • Check all gear and equipment after use and remove any visible algae. If you notice algae on your equipment at a later time, do not dispose of the algae by putting it down a drain. Dispose of it in the trash.
  • Dry all equipment thoroughly before entering a new body of water.
  • Drain water from live well and bilge before leaving access.
  • Report sightings of Rock Snot within our service area to Tip of the Mitt Watershed Council at  (231) 347-1181 or by e-mail [email protected]
Consider replacing felt-soled waders (left) with a new environmentally sensitive alternative (right) to help prevent the spread of this and other aquatic invasive species.
Additional Resources: