Pelagic Organism

Pelagic Organism


a plant or animal that inhabits the open sea and the surface of a lake, sea, or ocean—the pelagic zone. Pelagic organisms are contrasted with benthic ones, that is, benthos. They are divided into organisms that passively float on the surface of the water (pleuston) or in its depths (plankton) and organisms that swim (nekton). A distinction is also made between holopelagic organisms, which inhabit the pelagic zone throughout their entire lifetime, and meropelagic organisms, which dwell in the zone only temporarily. The latter include the planktonic larvae of benthic animals and adult benthic animals that float up to the pelagic zone during reproduction.

Many pelagic organisms have adapted similarly to life in the pelagic zone. For example, they are characterized by adaptations that make possible buoyancy and motility. Buoyancy is made possible by the gas bubbles of algae, the gas chambers of siphono-phores, the swim bladder of fish, and the water-filled, gelatinous tissues of coelenterates and tunicates. An abundance of fat in the cells and tissues of pelagic organisms also provides for buoyancy. Motility is made possible by the cilia of protozoans and many larvae, the fins of fish and cephalopods, and the torpedolike body of many nektonic animals.

Pelagic plants (phytoplankton) are the principal producers of organic matter in bodies of water, providing food (directly or though food chains) for aquatic animals. The skeletal remains of pelagic organisms form part of the ocean’s benthic sediments (diatomaceous, radiolarian, foraminiferal, and pteropodous oozes).


References in periodicals archive ?
Moreover, mangroves ecosystems are the nursery for many pelagic organisms, which are at the beginning of the food chain in coastal waters.
This is less than the global capture resulting from pelagic organisms - a figure that ranges from 0.
1939) stated that diurnal vertical migrations have long been known to play an important part in the lives of pelagic organisms.
Some of its inhabitants are suspended in the water, either swimming or drifting, and are called pelagic organisms.
Furthermore, many pelagic organisms interact with the seafloor and many benthic organisms leave the substrate and make regular incursions into the water column.
Pelagic organisms are subject to the general properties of the marine environment: its fluidity and instability; the easy conduction of dissolved materials, including nutrients and externally diffused active substances (pheromones); and the propagation of compressional (pressure) waves.
In general, pelagic organisms show greater diversity in tropical regions than in temperate ones, which in turn show more diversity than cold ones, However, especially on the continental platforms, the specific diversity of pelagic organisms in each biogeographical region is lower than that of their benthic equivalents.
Despite this, predation is intense and most pelagic organisms are eaten before they reach adult age.
Pelagic organisms in these areas have very short reproductive seasons, and in the case of the herring (Clupea harengus) it only lasts two or three weeks.
Not all marine mammals eat mainly pelagic organisms.