I'm not an expert on algae and plants. In fact, I've always thought Cecil and Bill Cody knew more than me. So, take this with a grain of salt.
As I read this string, I thought of the natural progression that occurs in our waters from green algae to blue-green algae as water warms. Green algae "bloom" at cooler temps, and then are replaced later by the blue-green algae blooms as water warms.
The two most common filamentous algae mats around here are Cladophora and Spirogyra. Those are both genus names (I'm not even sure if they have common names). If you grab some of your filementous algae and rub it between your fingers, the Spirogyra will feel "greasy" while the Cladophora will feel rough.
Anyway, I do have a point. :-) Both Spirogyra and Cladophora are green algae. So, the temperature stuff as discussed above may just apply.
