(Spirogyra, Anabaena, Oscillatoria, Lyngbya, Pithophora)
Filamentous algae have an appearance similar to that of stringy hairs or cotton.
Filamentous algae are easily identified by their stringiness; they are colonies of algae that link together to form a chain. They tend to begin growing along the bottom or attached to things such as rocks or sticks. They come up from the bottom and bubble before settling on top of the water. Nutrients in the water directly feed the algae, and large mats can form in the warm summer months when fertilization rates are higher. When there are large amounts of filamentous algae it is often described as looking like wet wool.
Filamentous algae can be found across the United States.