Like land plants and seagrasses, green algae contain chlorophylls a and b, the dominant pigments that provide these organisms with their characteristic colour. These special pigments are used to capture sunlight and convert it to chemical energy used to fix carbon dioxide into sugars (photosynthesis). Green algae store excess sugars as starch.
Macroscopic species are featured in this section, but numerous green algae are microscopic, single-cell forms. One of these is Chlorella-like zoochlorellae, which live in the tissues of certain anemones (CN13–15) along with the single-celled zooxanthellae (dinoflagellates) belonging to the genus Symbiodinium. These symbionts give the burrowing anemone (CN15), shown in the photograph, a green colour. Another single-cell alga, the free-floating Tetraselmis, is responsible for the “pea soup” colour in some seashore pools just above the direct influence of the tides.
Although most green algae live in fresh water, at least 130 species inhabit Pacific Northwest marine waters.
NOTE: Identification of many green algae to species can be difficult, and usually requires microscopic examination.