Mission: Rock snot

Research Question

Is didymo in Maine?

Photo by Flickr user Br3nda

You’re invited

Maine Department of Environmental Protection and Vital Signs invite you to be part of Maine’s front line detection effort for didymo! Didymosphenia geminata - also known as didymo or rock snot (eww!) - is a highly invasive colonial diatom (a single-celled algae) that is present in every state and province surrounding Maine. It loves swift moving water favored by fishermen, and has been tracked around the world on the bottom of felt-soled waders.

Mission steps

Fish and Game New Zealand

    1. Print the VS species ID card for rock snot and the US EPA's Fact Sheet to learn how to identify didymo

    2. Print a Freshwater Species Survey datasheet

    3. Go out and look for goo with the texture of wet wool growing on the rocks in your favorite fast-moving stream

    4. Add your "found" or "not found" observation through your My Vital Signs page (link at top right)

    5. Check out Mission: Analysis to figure out how your observation fits and what it means

Why this Mission Matters

NZ Department of Conservation

Didymo can form dense mats covering the bottom of rivers and streams, significantly altering the habitat for the native plants and animals. Species like crayfish that prefer rocky bottom habitats, or fish that spawn (reproduce) on rocky bottom stream and riverbeds are particularly harmed. Macroinvertebrates like stoneflies, mayflies, and caddisflies can also be displaced by Didymo.

Didymo has been documented in New Hampshire, Vermont, and New Brunswick, Canada, but not yet in Maine. A simple saltwater solution or a thorough drying-out kills it on waders, but eradicating it once it is established is another story.

Want to know and do more?

Southland NZ Fish and Game

US Environmental Protection Agency
Didymo has the national government's attention!

Maine’s Volunteer Lakes Monitoring Program
Didymo and other invaders on Maine's radar

Maine Department of Environmental Protection
Paul says "Just say no to didymo!"

VS blog: LL Bean boot design overhaul
Rock snot has lost a favorite vector!



I have a little stream in the back of my house. I don't know If I have it. I'll try and keep an eye out for it.

I may not be able to do this, and if i cant im still gonna try

i did not fined rock snot in Waterboro ME.

Dose Rock Snot have a card like Purple Loosestrife does that shows the info?


A new didymo card is ready for you to use! You'll find the link to it above under "Mission Steps." Thanks for the nudge to finish this card in time for the spring field season.

And thanks, too, for letting me know that you're using a different username for your solo investigations outside school. I look forward to following what you're up to.