Marine Biology (2+1)

Based on the mobility

Based on mobility or movement, benthos are grouped into sessile or attached, sedantary and vagrant.

Sessile organisms are those that do not have any mobility, attached or fixed firmly with the substratum or bottom of the aquatic environments and rely on currents or other mechanisms to bring food to them.

Plants such as benthic algae (seaweeds) and sea grasses and animals such as corals, other attached forms such as barnacles, oysters, etc. are the typical examples for sessile organisms. Sedantary benthos include all the slow moving animals like snails and nudibranchs.Vagrant benthos are those that have locomotory powers and they can move very rapidly on the substratum (e.g. shore crabs). Only animals are included under this category.