Hypoxic meiobenthic communities of the Istanbul Strait’s (Bosporus) outlet area of the Black Sea

Meiobenthos abundance and distribution on the Black Sea shelf and the upper slope area off the Bosporus Strait outlet was studied along a depth transect from 75 to 300m water depth. This study represents the first detailed quantitative analysis of the structure and distribution of meiobenthos communities in the transition zone from oxic to anoxic conditions in the Bosporus outlet area of the Black Sea. Meiobenthos was present at all investigated depths and includes 21 taxa. Among these the Nematoda was the dominant taxon. The maximum of total meiobenthos was located at 75m, other peaks occured at 88 m, 103 m, 160 m, 250 m. At 300 water depth of 300 m the amount of the meiobenthos significantly decreased, while the abundance of such groups as the Ciliophora and Nematoda showed a relative increase in abundance extension. Essential taxonomic richness and abundance of meiofauna is observed in the sediment from the surface layer to 5 cm depth. These results suggest that some benthic eukaryotes can tolerate anoxic and sulfidic conditions. Further studies of this region’s fauna are needed to yield more information about the taxonomic composition of benthos in the transitional oxic/anoxic water masses of the Black Sea.