Plankton

Plankton, microscopic marine animals and plants. They drift under the influence of ocean currents and are vitally important links in the marine food chain. A major part of plankton comprises minute plants (phytoplankton), mainly algae but including dinoflagellates and diatoms. Phytoplankton may be so numerous as to color the water and cause it to have a “bloom.” They are eaten by various animals (called zooplankton) that are in turn an important food for large animals, such as whales, and countless fishes. Phytoplankton is confined to the upper layers of the sea, where light can reach, but zooplankton has been found at great depths.