Distribution and Frequency of Macrobenthic community in Southern Coasts of Caspian Sea (Astara-Chaboksar)

Monitoring of benthic communities is important factor in ecosystem health studies. The Caspian Sea is considered as an independent zoogeographical region due to its diversity, specificity and endemism of its fauna. For studying frequency and distribution patterns of macrobenthic community, 5 transects along the Southern Coasts of Caspian Sea from Astara to Chaboksar were sampled. In each transect 3 stations with the depth of 1,5 and 10 meters were selected in perpendicular line to the beach .Physical parameters such as Temperature, Salinity, Dissolved Oxygen and pH were measured in addition to sediment grain size. Sampling has done twice a year (winter 2014 and summer 2015).Totally 38 macro benthos species were identified. Gastropods of Hydrobiidae family and polychaet Streblospio gynobranchiata were the dominant group with the contribution of 80% of total macrobenthos population. Average number of total benthos was 2250 individual/m2 in winter and 2630 individual/m2 in summer. Non-parametric statistical tests showed significant difference between number and frequency of species in different depths (p<0.05). Similarity coefficients and hierarchical analysis determined depth and salinity as the most effective factors. Canonical correspondence analysis confirmed this result and mentioned the grain size of substrate as an important one. Difference in slope of shoreline was another determining factor. Final results showed that sandy bottoms with lower number of macro fauna like amphipods and more dissolved oxygen are frequent in shallow waters and deeper muddy bottoms have characteristics of lower oxygen and more salinity with polychaeta and Gastropods in high numbers.