Sea anemones thrive in the intertidal zone of Santa Barbara County beaches due in part to microscopic organisms living within their bodies. A type of alga called zoochlorella grows inside the tissue of the anemones in a symbiotic relationship. Zoochlorella consumes carbon dioxide and nitrogenous and phosphorous wastes and in turn provides oxygen and nutrients to the anemones. Zoochlorellae are a type of green algae and its their presence that results in the green hue seen in anemones. Another type of alga, zooxanthella, is also found within sea anemones to a lesser extent and imparts a brownish tinge to their hosts.
Because the algae produce food through photosynthesis the sea anemones are dependent on sun exposure to sustain the microscopic plants within themselves so that they in turn feed the anemones. A scientific study conducted in Santa Barbara County waters of the Pacific Ocean suggests that sea anemones are able to survive lengthy periods of time without capturing their own food, because the algae provides sufficient nutrients for them. The anemones depend on photosynthesis for nourishment as much as they do catching their own food.
A Snail’s Odyssey: A scientific account of the biology of shallow-water, benthic-marine invertebrates on the west coast of North America.