Division Chlorophyta (Green Algae)

Many different forms including unicellular (non-motile and flagellate), filamentous, and macroscopic (sea lettuce); common in fresh water and marine environments; not always green in color, e.g. bright red snow algae (Chlamydomonas nivalis) and orange Trentepohlia on trunks of Monterey cypress; also includes extreme halophilic species (Dunaliella and Dangeardinella) and the most common photobiont (autotrophic symbiont) found in lichens (e.g. Trebouxia); unicellular green algae also grow inside the hollow hairs of polar bears, giving their fur a greenish tinge; the term zoochlorellae refer to several species of symbiotic green algae of the division Chlorophyta; along the Pacific coast of North America, zoochlorellae produce the pale greenish color in sea anemone tentacles.

Division Phaeophyta (Brown Algae)

Includes macroscopic seaweeds or kelps (e.g. Macrocystis, Pelagophycus and Laminaria); harvested for the natural polysaccharide gums algin and laminaran; contain the pigment fucoxanthin.

Division Pyrrophyta (Dinoflagellates)

Flagellated cells with conspicuous transverse groove; occur in blooms causing red tide and bioluminescence in ocean water; a wide variety of marine invertebrates, including sponges, jellyfish, sea anemones, corals, gastropods and turbellarians harbor within them golden spherical cells termed zooxanthellae; the photosynthetic activity of these symbiotic algal cells is vital to the survival of the individual coral animals and to the entire reef ecosystem; the zooxanthellae include several species of unicellular algae in the order Zooxanthellales within the algal division Pyrrophyta (also spelled Pyrrhophyta).

Division Chrysophyta (Diatoms)

Cells with ornamented silica valves which fit together like a microscopic Petri dish; along with the dinoflagellates an extremely important member of the ocean food chain and estimated to produce more than 70% of the earth's atmospheric oxygen.

Division Rhodophyta (Red Algae)

Contain the red pigment phycoerythrin and able to photosynthesize in deep waters of the euphotic zone; many beautiful macroscopic species; do not have centrioles or flagella; some species form bulk of algal reefs.

Division Euglenophyta (Euglena)

No true cell wall; cells animal-like and classified as flagellate protozoan by some zoologists; some species contain contractile vacuoles to expel water and exhibit cell-engulfing (phagocytosis).

Division Charophyta (Chara)

Interesting macroscopic algae with prominent sex organs; found in fresh water ponds throughout San Diego County, California; sometimes placed in the Division Chlorophyta along with the green algae.

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