Diversity and geographical distribution of soft-bottom macrobenthos in the bay of Bou Ismail (Algeria, Mediterranean Sea)

Abstract

The macrobenthic fauna in the bay of Bou-Ismail (Mediterranean Sea, Algeria) was studied with the objective of establishing a reference state based on the probable diversity thirty years earlier at the end of the 1980s. A total of 98 points were sampled using a Smith Mac Intyre grab sampler (two replicates each of 0.1 m2 and using a 1 mm mesh sieve). A total of 17,120 individuals representing 840 taxa (including 723 species) were identified from the sampled material. Seven distinct benthic communities were identified as a function of the sediment characteristics. Four diversity indices (Taxonomic Richness, Shannon, Pielou and ES(50)), and two benthic indices (AMBI and BO2A) were calculated for each of the seven benthic communities. Coastal Terrigenous Mud contains the poorest community while Muddy Detritic supports the richest variety. The Shannon index exceeds 6 at the sampling points with the greater diversity, where the number of individuals per 0.2 m2 reaches 664. Out of 50 organisms collected in a sample, the expected number of species was 35 (ES50). Moreover, < 50% of the taxa were found at only one or two stations. Benthic indicators revealed a good and high ecological status. The geographic origin of the 723 species is presented as their reported presence in 13 geographical regions including nine areas of the Mediterranean Sea. Most of the species had an Atlantic origin and are present in the western Mediterranean Sea.