Plankton

Abstract Plankton are aquatic organisms living in the water column that drift, float, or swim only weakly. The term describes a lifestyle used by a tremendous diversity of organisms including plants, animals, and bacteria that range from less than 1 µm to more than 1 m in length. Several common categorization schemes are used to group plankton depending on shared ecological roles, size, and whether they are plankton for their entire lives, or only for a portion of their development. Despite this diversity, consistent patterns of plankton abundance have been documented throughout the world's oceans, both horizontally with distance from land, and vertically with increasing depth. Seasonal patterns of plankton abundance are also well known for many locations. Although individually small, planktonic organisms are numerous. In aggregate, they have global impacts. Plankton are the base of aquatic foodwebs, providing food for larger aquatic organisms, including commercially valuable species. Plankton influence global climate by taking in atmospheric carbon and releasing volatile sulfur compounds. They also supply half of the Earth's oxygen production. Finally, the remnants of plankton settle through the water column, eventually forming the sediments that cover most ocean bottoms.