Faunal communities in Mediterranean infralittoral coarse sediment

This habitat is usually associated with the mouths of big rivers and streams, but it is also found as a fringe close to the rocky margins in bays and adjacent to coarse sandy beaches (4-25 m depth) in exposed areas subjected to strong unidirectional bottom currents and/or wave action. The high exposure that this habitat experiences prevents the accumulation of organic matter and fine sediments. Coarse sediments provide a wide range of interstitial spaces that constitute a suitable habitat for many invertebrates, mainly carnivores, omnivores and filter feeders.

Bivalves (Spisula subtruncata, Lucinella divaricata, and in some cases Loripes lucinalis) are the most representative group of this habitat type, but infaunal polychaetes are also very abundant (Aonides paucibranchiata, Spio decoratus, Protodorvillea kefersteini, Glycera tesselata, Lumbrinerides acuta, Aponuphis spp., Paradoneis armata and Mediomastus fragilis). The amphipod Siphonoecetes dellavallei is the most frequent crustacean, together with Apseudopsis latreilli, in areas close to Posidonia oceanica meadows. Nematodes are common and abundant mainly in bottoms shallower than 20 m depth. The polychaete Ditrupa arietina is rare at less than 10 m but it can be found within a wide variety of sediments, being more abundant at increasing proportions of coarse material. The bivalves Acanthocardia tuberculata and Callista chione are also characteristic species of this habitat, and constitute an important contribution to the total biomass. Fishes such as the Greater Weever (Trachinus draco), the Spanish Bream (Pagellus acarne), the Striped Seabream (Lithognathus mormyrus) and the Mediterranean Sand Eel (Gymnammodytes cicerelus) are also common in this habitat. A particular fauna assemblage of this habitat is composed by the Amphioxus or Lancelets (Branchiostoma lanceolatum). This “Amphioxus sands” normally extends on gravel and coarse sand with shell fragments.

Indicators of quality:                                                                                                                           

Most of the species included in the habitat description are indicators of good environmental quality. The majority of bivalves are very sensitive to environmental disturbances and changes in the density and structure of these communities might indicate a change on habitat quality.

In general, Branchiostoma lanceolatum communities show a negative correlation between the amphioxus presence and the organic matter content of the habitat, changing also the dominant species with the enrichment in the sediment.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats