Rock snot

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: http://eol.org/pages/11737/overview.

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: http://en.wikipedia.org/wiki/Algae."

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