Distribution and Seasonal Variation of Macrobenthic Community in Gorgan Bay (Southeast Caspian Sea)

Distribution and abundance of macrobenthic organisms in Gorgan Bay were seasonally investigated from winter 2004 till fall 2005. Samples were taken with a grab from 7 sampling stations. Sediment grain size and organic matter of sediments were measured and their relationship with the abundance and distribution of macrobenthic were analyzed. Seven group of macrobenthos were identified of which the most abundant order were Polychaeta(42%), Gastropoda(26%), Bivalvia(19%). The maximum abundance of macrobenthos was observed in summer (341 individual/m2), while the minimum was seen in winter (199 individual/m2). The maximum and minimum biomass was 42.36 g/m2 and 10.92 g/m2 in summer and winter, respectively. The average wet biomass of macrobenthos was 29.75 g/m2. Also the correlation test between abundance and biomass of macrobenthos with total organic matter and texture of sediments in sampling stations during the period of study were calculated. In the summer and winter macrobenthic abundance and biomass showed a negative relation with sand percentage and a positive relation with organic matter.