Invasive SpeciesRock snot

Didymosphenia geminata
FOUND by Equinox
ID Questioned
Quality checked by potatotree
Peer reviewed by potatotree
Field Notes
We see water and forests. We hear the stream and people talking. We smell nature. The problem we ran into, was that the water was getting deep.
Supporting Evidence
Photo of my evidence.
It had the right texture. It felt like wet wool.
Photo of my evidence.
The color matched to characteristics of the pictures online of rock snot. It was a brownish yellowish.
Photo of my evidence.
We found it in a fast moving stream, in the middle of the woods. And that is where it is most typically found.
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Didymosphenia geminata
Common name:
Rock snot
Count of individuals: 
Less than 1/4 covered
How big is it?: 
2 - 5 cm
Is it male or female?: 
Can't tell
Sampling method: 
Just looking around
Time search
Photo of our sampling method.
Place Studied
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Map this species
N 44.724547 °
W -68.623953 °
Observation Site Information
A photo of our study site.
Freshwater - In a stream or river
Trip Information
Mill Stream
Trip date: 
Thu, 2011-09-08 13:31
Town or city: 
Type of investigation: 
Species and Habitat Survey
Eastern Coastal
MIDAS Code: 
Habitat Observations
Species diversity: 
20 different species
Evidence of vectors: 
Boat ramp
Carried down stream by current.
Water temperature: 
Dissolved oxygen: 


Maine DEP's Dr. Tom Danielson adds this: "The sample did not contain the invasive Didymosphenia geminata, which is great. The most common alga was a chain forming Fragilaria, which is a diatom. Diatoms have 2 shells made of silica called “raphes”, kind of like the top and bottom parts of a petri dish. Phycologists identify diatoms by the size, shape, and ornamentation of the raphes.

I tried getting some pictures, but the microscope camera is still not working properly. Here is a web site that has some good pictures:

These pictures show the Fragilaria cells stuck together to form long chains. The golden colored shapes within the cells are the chloroplasts where photosynthesis takes place. Fragilaria, like all diatoms, has chlorophyll in the chloroplasts, which is green, but also have additional photosynthetic pigments that give the chloroplasts the golden-brown color. Some of the pictures have scale bars with micrometers as the unit (e.g., 20 um). One micrometer (um) is equivalent to 1 millionth of a meter. In other words 1,000,000 micrometers equals 1 meter.

I typically find Fragilaria chains in healthy streams with low to moderate levels of nutrients. They are more common in streams and rivers with water that is somewhat stained (tea-colored), rather than very clear.

More general information about algae can be found at the following website:"

Hi Paul,

We thought that you would want to check out the video that the 8th grade citizen scientists at Dedham School made. It's in the project bank. Here's a direct link -

It's pretty awesome!

Thanks again to Paul and all the great student scientists at Dedham School for all the hard work you do. We're glad you have fun doing it!

Dear Equinox,

First, thank you for mailing me the alga sample the other day. It arrived in perfect condition such that one of my colleagues, an algae specialist, was able to examine the sample.

All your clues about identifying this a didymo were spot one: the location where you found it was ideal habitat, and the texture and color were indeed similar to didymo. Frankly, I was a little nervous that your may have discovered Maine's first population of didymo.

Thankfully, closer inspection thru a microscope confirmed that this was NOT didymo. (Yay!) Your sample is, however, a relative of didymo. More specifically, it belongs to the same family of algae (diatom) and has a similar filament or ribbon-like shape (known as fragillaria).

So you were close, but no didymo.

While I'm at it, here's a fun fact: Did you know that all algae (freshwater and marine) have played and continue to play a major role in producting our planet's supply of oxygen? Some scientist feel that they produce more oxygen than all of the world's plants combined?

--Paul, Maine Department of Environmental Protection Invasive Species Program

Hmmm...there's no way I can identify this by way of your picture. However (!), the setting appears ideal for Didymo, and your description--wool-like texture--got my attention! It's definitely worthy of further scrutiny.

Can you mail me a sample for me to share with DEP colleagues? Simply bag in a small zip-lock freezer-type bag with a wet paper towel and mail to me on a Monday (so it doesn't spend an entire weekend in the post office). Be sure to note where you grabbed the sample, your name, and phone number so I can call you with the specimen's identity.

Here's my address: Paul Gregory, Maine DEP Invasive Species Program, 17 State House Station, Augusta ME 04333. If you have questions, call me: 441-0627.

I look for to receiving your mystery alga! --Paul