fa یافته علمی کوتاه : الگوی پراکنش و فراوانی مکانی و زمانی ماکروبنتوزهای سواحل جنوبی دریای خزر (ساحل شهرستان چالوس) بهداشت و بيماريهاي آبزيان بهداشت بيماريها پژوهشي Research The changes in density and biomass of macrobenthos were seasonally investigated from winter 2005 till fall 2006 in southern Caspian Sea. Samples were taken with a 225cm2 Van Veen grab from depths of 7 and 20 meters along two transects: Line 8 area (western part) and Radio Darya area (eastern part). Totally, 5 classes of macrobenthos were identified of which the most abundant populations were Polychaeta 68.7%, Oligochaeta 14.6%, Bivalvia 8.5%, Crustacea 8.2% and Gastropoda 0.08%. The maximum density (4251.8 1419 (ME SE) ind/m2) of macrobenthos was observed during summer in the depth of 20m of Radio Darya area, while the minimum density (725.9 64.5 (ME SE) ind/m2) was observed during spring in the depth of 7m in the same area. Between the two studied depths, the mean annual density in 7m depth (2266.7 350.3 (ME SE)ind/m2), was higher from 20m depth (1977.8 290.1 (ME SE)ind/m2). The maximum biomass (475 243.8 (ME SE)g/m2), of macrobenthos was observed during autumn in the depth of 20 meter of Radio Darya area, while the minimum biomass (0.3 0.1 (ME SE)g/m2), was observed during winter in the depth of 7m in the same area. Between the two studied depths, the mean annual biomass in 20m depth (184.8 24.6 (ME SE)g/m2), was higher from 7m depth (73.7 24.6 (ME SE)g/m2). Generally speaking, the eastern part of Chalus coast had more density and biomass compared with the western part. *Corresponding author Biomass, Macrobenthos, Ecology, Caspian Sea 147 152 http://isfj.ir/browse.php?a_code=A-10-83-18&slc_lang=fa&sid=1 M. Tavoli میثم طاولی eysamtavoli@yahoo.com 100319475328460016305 100319475328460016305 Yes M. Islami مریم اسلامی 100319475328460016306 100319475328460016306 No S.M. Mahdavi سید مصطفی مهدوی 100319475328460016307 100319475328460016307 No