Distribution of soft-bottom polychaetes of the Levantine coast of Turkey, eastern Mediterranean Sea

A study of the spatio (three transects: each transect consisted of depths of 10, 25, 50, 75, 100, 150 and 200 m), seasonal (February, May, August and November) distribution of polychaetes was conducted on soft bottoms of the Levantine Sea shelf in 2000. A total of 184 Polychaeta species were found, of which 12 species were new records for the Turkish fauna, 72 species for the Turkish Levantine coast. Species richness encountered in winter was higher than that in other seasons. Species richness also varied along the shelf depth gradient, with the highest values found between 50 and 100 m. Abundances of polychaetes were higher in warm seasons (August and November) and peaked at depths of 25-50 m, whereas biomass was higher in May and August, and peaked at 50 m. Evenness index values showed a seasonal variation at depths shallower than 75 m, whereas it seemed to be more stable in deeper waters in all seasons. In the studied area, there were three main polychaete assemblages occurring: shallow waters (10-25; 50 m), intermediate zone (75-100 m), and deep waters (150-200 m). Depth was the main factor governing the distribution of polychaetes in the area. In addition, the grain size of the sediment and Total Organic Carbon (TOC) also significantly affected the polychaete composition and abundances.