Invasive SpeciesRock snot

Didymosphenia geminata
NOT FOUND by bmcweeny
ID Confirmed
Quality checked by Bill McWeeny
Peer reviewed by
Field Notes
I walked up a stream bed because it has running water many times during the year. There were many rocks in the bed exposed so that rock snot could take hold. I found nothing like the rock snot described on the ID sheet.
Supporting Evidence
Photo of my evidence.
None of the rocks I saw had the green and yellow colors of rock snot.
Photo of my evidence.
I felt the rocks and they were not jelly like. Some were slippery but green.
Species Observation: Species Looked For
Did you find it?: 
I think I did not find it
Scientific name:
Didymosphenia geminata
Common name:
Rock snot
Sampling method: 
Just looking around
Photo of our sampling method.
Place Studied
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Map this species
N 44.399203 °
W -68.716907 °
Observation Site Information
A photo of our study site.
Upland - Forest
Trip Information
Green's Cove
Trip date: 
Wed, 2014-09-24 15:30
Town or city: 
Type of investigation: 
Species Survey
Time of low tide: 
Wed, 2014-09-24 16:45


Yes, it's always good news to read that didymo has NOT been found. So far--touch wood--no didymo has been found in Maine. Where it has in neighboring states and provinces, it's been detected in flowing streams with rocky bottoms--perfect trout fishing waters.

That's why it's important that the fishing community know that their boots--especially felt soled boots--are effective vectors for transporting the invasive alga from stream to stream.

Which leads to Moss Boss's correct contribution: didymo is a strictly freshwater alga. The non-profit Fly Fishing in Maine has set up pilot wash stations a key fishing locations which invite folks to scrub their boots with a salt solution. Now salt is not the most effective algaecide, but it's one Maine DEP can endorse because of its acceptable toxicity to other critters and immediate habitat when used as a scrubbing bath for boots.

Thanks for looking! Maine can't brag it's didymo-free without useful observations such as yours. And what a beautiful place for you to explore! --Paul

Hi folks,

Actually the stream is up hill from the marsh I showed as the study site so there is no salt in it.

Thanks, Bill

I love your study site photo! How cool is that? Also, nice not found observation. I'm curious how salty the water is where you are, it looks like you're in an estuarine environment? I've heard something about didymo being killed by high enough salinity conditions. Apparently it's a treatment for preventing its spread from gear.

Cheers and happy observing!