Dark color indicates abundant diatoms within the blue-green algal felt. At somewhat slower flow vertical pinnacles form. These are buoyed by gas bubbles, but also firm enough to stand up without being buoyed. Darker colors indicate increased diatom abundance. Abundant pinnacles of blue-green algae and diatoms in calmer water.
Gas bubbles provide buoyancy.
Close-up of green algal bottom cover. Detail view of algal filaments. The large cell size indicates that it is a green algae, and the spiraling chloroplast indicates a species of Spirogyra . Fluorescent light picture. The chloroplast fluoresces red because of photosynthetic pigments.