Biocenosis of Mediterranean mediolittoral coarse detritus

Description (English)

Mid-beach with stones and pebbles, with a vertical extension that is usually slight.
Mid-beach pebbles which retain between them plant debris thrown up on the beach as wrack. Possible site for Posidonia banks.
This area goes through periods of alternating submersion in and emergence from the water during calm weather because of variations in the water level, and is frequently moistened by wavelets. The vertical size of the rise and fall of the water, which can be some dozens of centimetres, can mark out strips several metres wide on the beach.
The habitat can present variations according to the granulometric size in the substratum, the hydrodynamic action produced by the backwash and the quantity and quality of detritus thrown up on the beach as wreckage.
The population dynamics vary according to the humectation of the environment and, especially, the level of wave energy since hydrodynamics are the vector of the dampness and of the quality and quantity of detritus that can be used for food as well as sedimentation. Powerful hydrodynamics encourage the laying down of a coarse sediment. The fauna is basically made up of scavengers of detritus and their predators, and so essentially unstable. It is characterised by two crustaceans, the amphipod Echinogammarus olivii and the isopod Sphaeroma serratum.

Source: EUNIS habitat classification