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Protecting Northern Michigan's ​Water Resources

Rock Snot (Didymo)

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.

Scientific Name:

Didymosphenia geminata

Identification 

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. 
 
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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.

Table of Contents

Origin & Dispersal

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 info@watershedcouncil.org
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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:

Reporting Invasive Species – FREE APP 
Midwest Invasive Species Information Network (MISIN)

Smartphone App

The MISIN smartphone app provides a mobile solution for the capture of invasive species field observation data. You can play an important role in the early detection and rapid response to new invasive threats in your area by contributing invasive species observations to the MISIN database. 

  • Identify and report 200+ invasive plant and animal species 
  • Capture and submit species observations from the field 
  • Include images taken in the field with your observation 
  • Browse images and species information on the top Midwest invaders
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