nekton

Nekton refers to the aggregate of actively swimming aquatic organisms in a body of water (usually oceans or lakes) able to move independently of water currents.

Nekton are contrasted with plankton which refers to the aggregate of passively floating, drifting, or somewhat motile organisms occurring in a body of water, primarily comprising tiny algae and bacteria, small eggs and larvae of marine organisms, and protozoa and other minute predators.

As a guideline, nekton are larger and tend to swim largely at biologically high Reynolds numbers (>10^3 and up beyond 10^9), where inertial flows are the rule, and eddies (vortices) are easily shed. Plankton, on the other hand, are small and, if they swim at all, do so at biologically low Reynolds numbers (0.001 to 10), where the viscous behavior of water dominates, and reversible flows are the rule. Organisms such as jellyfish and others are considered plankton when they are very small and swim at low Reynolds numbers, and considered nekton as they grow large enough to swim at high Reynolds numbers. Many animals considered classic examples of nekton (e.g., Mola mola, squid, marlin) start out life as tiny members of the plankton and gradually transition to nekton as they grow.

Oceanic nekton

Oceanic nekton comprises animals largely from three clades

• Vertebrates form the largest contribution, these animals are supported by either bones or cartilage.
• Mollusks are animals such as squids and scallops.
• Crustaceans are animals such as lobsters and crabs.

Etymology

The term nekton was coined in 1890 by Ernst Haeckel; it is rooted in the Greek adjective νηκτός nēktós ("the swimming") derived from the verb νήχειν nḗkhein ("to swim"). The study of swimming organisms (biofluidynamics, biomechanics, functional morphology of fluid locomotion, locomotor physiology) is called nektology. One who studies swimming in all its forms is called a nektologist.

See also

• plankton (the organisms that float or drift within the water)
• neuston (the organisms that float on the water)
• benthos (the organisms at the bottom of a body of water)

External links

• Stefan Nehring and Ute Albrecht (1997): „hell und das redundante Benthon: Neologismen in der deutschsprachigen Limnologie“. In: Lauterbornia H. 31: 17-30, Dinkelscherben, Dezember 1997 E-Text (PDF-Datei)

Aquatic ecosystems – general and freshwater components General Aquatic ecosystems Acoustic ecology Agent-based models Algal bloom Anoxic waters Aquatic adaptation Aquatic animals Aquatic biodiversity research Aquatic biomonitoring Aquatic insects Aquatic layers Aquatic mammals Aquatic plants Aquatic predation Aquatic respiration Aquatic science Aquatic toxicology Benthos Bioluminescence Biomass Cascade effect Colored dissolved organic matter Dead zone Ecohydrology Eutrophication Fisheries science Food chain Food web GIS and aquatic science Hydrobiology Hypoxia Isotope analysis Microbial ecology Microbial food web Microbial loop Nekton Neuston Particle Photic zone Phytoplankton Plankton Productivity Ramsar Convention Schooling Sediment trap Siltation Spawning Substrate Thermal pollution Trophic level Underwater camouflage and mimicry Water column Zooplankton More... Freshwater Freshwater ecosystems Brackish marsh Freshwater biology Freshwater biomes Freshwater fish Freshwater marsh Freshwater swamp forest Hyporheic zone Lake ecosystems Landscape limnology Limnology Lake stratification Macrophyte Pond Fish pond Rheotaxis River ecosystems Stream bed Stream pool Trophic state index Upland and lowland Water garden Wetland Environmental quality More... Ecoregions Freshwater ecoregions List of freshwater ecoregions Marine ecoregions List of marine ecoregions Ecology of the Everglades Ecology of the San Francisco Estuary Ecosystem of the North Pacific Subtropical Gyre Freshwater ecology of Maharashtra   Aquatic ecosystems – marine components Marine Marine ecosystem f-ratio Iron fertilization Iron Hypothesis Large marine ecosystem Marine biology Marine chemistry Marine snow Ocean nourishment Oceanic physical-biological process Ocean turbidity Photophore Thorson's rule Upwelling Whale fall More... Marine life forms Census of Marine Life Coastal fish Coral reef fish Deep sea communities Deep sea creature Deep sea fish Deep water corals Demersal fish Marine bacteriophage Marine invertebrates Marine larval ecology Marine mammal Marine reptile Marine vertebrate Paradox of the plankton Pelagic fish Seabird Seashore wildlife Wild fisheries Marine habitats Bay mud Black smokers Coastal biogeomorphology Cold seeps Coral reefs Davidson Seamount Estuaries Intertidal ecology Intertidal wetland Kelp forests Hydrothermal vent Lagoons Mangroves Marine biomes Marine habitats Mudflat Rocky shores Salt marshes Seagrass meadows Sponge reefs Tide pools Issues Ecological values of mangrove Fisheries and climate change HERMIONE Marine conservation Marine conservation activism Marine pollution Marine Protected Area