A variety of phytoplankton species, greatly magnified Plankton are tiny plants and animals that float or swim in the surface waters of the ocean. Most ocean animals depend on them, either directly or indirectly, for their food. Plant plankton is called phytoplankton; animal plankton is known as zooplankton. Algae, simple, single-celled, plant-like organisms, form a major part of phytoplankton. Unlike land plants, oceanic plants cannot put down roots into the ground. Instead, they drift through the water. They use sunlight and nutrients dissolved in the water to make food by the process of photosynthesis.
Diatoms viewed through a microscopeMost phytoplankton consists of organisms called diatoms, the commonest types of algae. These are very simple life-forms, no bigger than a tenth of a millimetre in size. Seen under a microscope, however, they have beautifully detailed patterns. Delicate “hairs” or whip-like “oars” help keep them floating at or near the water’s surface as they drift along in the currents.
There are estimated to be around 100,000 species of diatom.
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