The study of distribution and frequency of Polychaeta in southern coasts of Caspian Sea (Astara-Bandar Torkaman)

The study is Considering the importance of the role of benthic communities in evaluating the ecological status of aquatic ecosystems and part of a research project in the southern coasts of the Caspian Sea (depths less of 30 meters) was conducted in 2019. The aim of this study was investigation of the distribution, density and biomass of macrobenthos organisms in the water at a depths of 5, 10 and 30 meters south Caspian Sea. Sampling was seasonaly at eight with using Van Veen Grab. Overall 34443 organisms of Polychaeta including 3 families, 4 genuses and 4 species. The results showed that the highest density at Sefidrood station with mean of 327±27.71 N/m2 and lowest was at Bandartoraman station with mean 77±5.33 N/m2. The highest of Polychaeta was in summer and depth 30 meters with mean 285±26.18 N/m2 and lowest density in spring and depth 10 meters with mean 38±10.81 N/m2. The highest biomass was in spring and depth 30 meters with mean 0.23±0.02 g/m2. The highest species was assigned to S. gynobranchiata with mean 352±19.74 N/m2 and frequency 80%. In general, the results showed that in most seasons of the year, S. gynobranchiata was the dominant Polychaeta species.