Abundance of macrobenthos and its relationship with environmental factors in Gorgan Bay mouth (southeast of Caspian Sea)

The purpose of this study was to investigate the population of benthic invertebrates and their relationship with environmental factors of Gorgan Bay Inlet. The abundance of benthic invertebrates during 2017 in three seasons from 9 stations in three sites, bay mouth, Ashuradeh coast and sturgeon culture area was studied using three replicates (225 cm2). In this study, in total, fauna was identified: 3 phyla, 6 classes, 12 families and 12 Genus. Streblospio gynobranchiata (2347±177, 47%) and Hediste diversicolor (873±101, 17%) had the highest abundance. The highest species abundance was observed in spring and the lowest species abundance in autumn. The lowest Shannon (1.12) and Pielu index (0.62) were obtained in the sturgeon culture area. Also, the dbRDA graph based on DistLM model showed that temperature, salinity and clay temperature variables and sand, silt and dissolved oxygen variables were responsible for causing abundance of fauna among different stations in the sampling seasons. According to these results, it can be concluded that macrobenthos in different seasons and areas have many changes in abundance and diversity index. Therefore, when using these communities to assess the impact of environmental factors, their natural changes should be considered.