Identification and biodiversity of macrobenthos Gharehsou River - Southeast Caspian Sea

This study was carried out to investigate microbenthic diversity and seasonal variation in two sampling areas including estuary and river stations during 4 season in 2010. Sampling was done using Van Ven Grab in 3 replicates and the collected samples were fixed in 4% formaldehyde. The results showed that there are 12 benthic taxa families belonging to 9 orders in the river station, in which the most frequent family was Lumbriculidae (19.39%), and Tubificidae has the lowest abundance (2.07%). While the estuary station contained 12 families belonging to 10 orders. The following families had high abundance: Ampharetidae (21%), Lumbriculidae (11.55%), Naididae (11.32%) and Gammaridae (9.98%). The highest and lowest abundance of macrobenthoses in the river station were observed in fall and in winter respectively, while in the estuary station the maximum and minimum were observed in spring and in winter. The maximum Shannon-Wiener index in the river were observed in the spring (2.36) and in the estuary was in the summer (2.13). The highest value of Simpson index in the river area was in the summer (0.19) and in the estuary area in the spring. Results of Richness index showed that the highest amount in the river was observed in the spring, while the highest amount in the estuary was obtained in the autumn. It can be concluded that river station had higher density and diversity than estuary, indicating better ecological conditions.