Study of distribution, density and biomass of Hypaniola kowalewskii in the Southern coasts of Caspian Sea

Caspian Sea is the biggest lake in the world among Iran. Torkamanestan, Ghazaghestan, Russia and republic of Azerbaijan. There have been many and different studies on Mazandaran Sea macrobenthic that occurs in different deeps of the sea and times. The purpose of this study was to investigate of density and biomass Hypaniola kowalewskii in substrate sediment of different transects (from Babolsar to Babdar-e-Torkaman). Macrobenthic were sampled using a Van Veen Grab (۱۵×۱۵ cm۲) in Southern coast at ۳ station and ۳ depths (۵, ۱۰ and ۳۰ m) during two seasons in ۲۰۱۹. The results showed that density and biomass of Hypaniola kowalewskii was in autumn and winter (respectively) with mean ۳۵±۰.۰۱۷ ind.m۲, ۰.۰۱۷±۰.۰۰۷ g.m۲ and ۱۷۳.۳۳±۴۰.۴۰ ind.m۲, ۰.۰۵۴±۰.۰۱۲ g.m۲. There was a significant difference between the density and biomass between two seasons (p<۰.۰۵). The results also showed that, in spring and summer the highest density and biomass in Bandar-e-Torkaman (respectively) ۲۰±۱۰.۳۹ ind.m۲ and ۰.۰۱۲±۰.۰۰۴ g.m۲; ۶۵±۱۱.۳۹ ind.m۲ and ۰.۰۲۲±۰.۰۰۴ g.m۲. According to our results, it can be concluded that density and biomass of macrobenthic communities vary greatly with season and depth. Therefore, natural fluctuations of these variables should come into account while using macrobenthic for environmental impact assessment.