Species Information


Didymo (a.k.a. rock snot)
Didymosphenia geminata

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  • There are a few North American records dating back to the late 1800's
  • First modern documentations in northeastern North America in Quebec, 2006
  • First nuisance blooms in northeastern North America documented in Batten Kill, NY, 2006; several rivers in Quebec and New Brunswick, 2007; and Connecticut River drainage of NH and VT, 2007
  • Nuisance blooms have occurred in several additional rivers and streams in the northeast in subsequent years

  • Tan, light brown or brown clumps or ropy strands
  • Feels rough, cottony or fibrous; does not feel slimy to the touch
  • Can form thick solid mats (1-4 inches) on rocks or stream bottoms, or may appear clumpy or feathery
  • Dried stalk material on shore may look like dried cardboard or toilet tissue
  • Definitive identification requires microscopic examination

  • Clear, swift-flowing rivers and streams with rocky bottoms
  • Often found in tailwaters below dams
  • Occasionally found in large lakes with continuous wave action

Known Distribution in the Northeast
  • Various rivers and streams in Quebec, New Brunswick, VT, NH, NY and CT

  • Alters the composition of aquatic insect communities in areas of heavy infestation
  • Degrades aesthetic quality of pristine streams
  • Heavy infestations may impact infrastructure such as clogging irrigation intake pipes
  • Although no direct impacts on fish communities have been documented, there is concern about potential long term impacts

400x Magnification

Protecting the marine and freshwater resources of the Northeast from invasive aquatic nuisance species