Benthos

In ecology, benthos (from the Greek βένθος/benthos, "seabed") is called the community formed by the organisms that inhabit the bottom of aquatic ecosystems. Benthos is distinguished from plankton and nekton, formed by organisms that live in the water column. The adjective that derives from benthos is benthic.

Where the light reaches the bottom, which depends on the depth and transparency of the medium, the community includes photosynthesizing primary producers. In the aphotic (lightless) environment of the deepest depths, all organisms are consumers, depending on the organic remains and microorganisms that gravity deposits from more superficial levels.

A special and notable case is that of biocenoses, more or less ephemeral, which are established at points of the central-oceanic ridges, at abyssal depths, where hydrothermal volcanism occurs, with the emission of very hot water loaded with you go out. In these ecosystems, primary production is carried out by chemosynthesizing bacteria, some free-living and others symbiotic with animals.

The most productive and most biodiverse benthic communities, and also probably the most threatened, are coral reefs. The disorganization and impoverishment of benthic communities by certain fishing gear, such as trawl nets, are among the greatest environmental problems.

Many notable taxa (biological groups) are specialized to reside in the benthos. The entire phylum of echinoderms (stars and sea urchins), for example, is made up of benthic forms. The order Pleuronectiformes (sole and similar) is an example of fish adapted to life in the benthos. Also octopuses or cuttlefish among the cephalopods, and the class of bivalves among other mollusks.

Many benthic organisms move, even if only slightly, for example clams or sea anemones. Others are directly sessile (fixed), such as oysters, corals, or coralline algae (a group of red algae); For the group formed by the organisms attached to the bottom we have the term, rarely used, efaptomenon, and for the rooted ones we have rhizomenon.

Power supplies

The main food sources in plankton and benthos are organic substances that arrive dragged from land. Water depth, temperature, salinity, and local substrate type determine the benthos found at each location. In coastal waters and other places where light reaches the bottom, photosynthesizing benthic diatoms can proliferate. Filter-feeding invertebrates, such as sponges and bivalves, dominate hard, sandy bottoms. Sedimentivores, such as polychaetes, populate soft bottoms. Fish, starfish, snails, cephalopods and crustaceans are important predators and scavengers.

Some benthic organisms, such as starfish, oysters, clams, sea cucumbers, ophiuroids, and sea anemones, play an important role as a food source for fish and humans.