The study of the effect of winter monsoon on the diversity of bivalves in the subtidal areas of the northern coast of the Makoran Sea (Ramin-Beris-Passabender)

The Oman Sea (Makoran) has always been influenced by the monsoon currents, and this phenomenon is a natural stressor for species inhabiting the marine ecosystem, including bivalve molluscs. To study the diversity of subterranean bivalves sampled from three areas of Ramin, Beris, and Pasabandar, a total of 10 stations, in the winter of Pre-Manson, Mansoon and Post Mansoon in 2018. In this study, 8 families of bivalve communities were identified that the Veneridae family had the highest frequency in all three time periods. According to the results, in post-monsoon bivalves were higher with 46.19% abundance (11400 abundance) than premonsoon month, 27.06% (6660 abundance) and the monsoon period with 26.74% abundance (26.74%) 6680 m2), which also showed significant difference analysis of variance. The mean of Shannon index in pre-monsoon, monsoon and post-monsoon were calculated 2.22±0.04, 2.21±0.1 and 2.51±0.11, respectively, but no significant differences were observed between different periods. Mean dominance index observed in pre-monsoon, monsoon and post-monsoon was calculated 0.86±0.06, 0.86±0.05, 0.9± 0.01, and between post-monsoon and other periods, respectively. The mean eveness index was calculated as 0.959±0.01,0.951±0.02,0.948±0.01 and the difference between the monsoon and pre-monsoon periods were not significant. In general, it can be said that various factors are considered as parameters controlling the abundance and diversity of bivalve communities of different regions and stations in the coastal waters of Chabahar Bay, including the most important ones. It can be noted the sampling time and the winter monsoon current.