The large community of microorganisms that floats freely in the surface waters of oceans, seas, rivers, and lakes. They are moved passively by wind, water currents, or waves, having little or no powers of locomotion themselves. The plant plankton (phytoplankton) includes many microscopic algae, particularly the diatoms. They form the base of the food chain in water, being eaten by the animal plankton (zooplankton), which in turn provides food for fish. It has been estimated that 90% of photosynthetic activity is carried out by the phytoplankton. A feature of the plankton is the huge variation in composition at different times of year (see bloom). |
