Benthos, a term derived from the Greek, means 'depths of the sea’. The Benthos is a group term for all the organisms and communities living at surface, and beneath the surface of the sea floor. These organisms are mostly invertebrates (organisms that have no backbones) such as the anthosa, octopus and sea star.
At the ocean floor, there is a complex interaction between living and non-living factors. Benthos can also occur in shallow waters.
Infauna includes the bacteria, plants, and organisms that live in the sediment or layer of particles at the sea floor. These are sediments such as fish droppings, dead organic matter, and rock debris that perhaps sink to the bottom of the sea. Examples of infauna include diatoms, worms, rasor clams, bivalve and decomposers such as bacteria and flagellates.
These are the organisms on the surface of the sea floor that attach themselves to the rocks and debris. Many of these living things (animals) can move. Epifauna plants such as seaweed also grow in the water towards sunlight, although they are usually attached to some rocks or hard substrate. Examples of Benthic epifauna includes mussels and snails.
There are also different types of fish that just live at the bottom of the ocean, feeding on infauna and epifauna. They are known as Demersal.
Food webs at the Benthos are very interesting in the sense that, sunlight usually does not get to that part of the ocean floor, yet there is a unique and complete interaction of biotic and abiotic factors there. For example most of the infauna and epifauna help to breakdown organic matter, enriching their environment with minerals and nutrients.