Species Information

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

  Click here for information at USGS!

History

• 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

Characteristics

• 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

Habitat

• 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

Impacts

• 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