Study of sub-tidal polychaetes density in winter monsoon on the northern coast of the Makoran Sea (Beris-Ramin-Passabandar)

Polychaetes are important in determining the environmental status of seabed and their role in the food chain. Sampling of sediments in three areas of Beris, Ramin and Pasabandar was performed at 10 stations in the north of the Makoran Sea by Garb van-veen during three periods of pre-monsoon, monsoon, and post-monsoon winter with recordings of chemical physical parameters from November to March 2016. In the study identified 18 families of polychaetes communities it was found that the highest density in Monson period and in Post-Monsoon with 4364.67 ± 570 ind/m2 and the lowest density in Post-Manson period in Roman region with 225.33 ± 89 ind/m2.  In the pasaBandar area, the highest percentages belonged to the families Spionidae, Maldanidae and Cirratulidae, and to the families of Nephtydae, Phyllodocidae and Cirratulidae and to the Ramin family's Orbiniidae, Maldanidae and Cirratulidae. One-way ANOVA showed significant differences between stations and time periods (P <0.05). The highest densities of the polychaetes were estimated in terms of the period of Monsoon> Pre-Monsoon> Post-Monsoon period, respectively. Results of correlation between polychaete density and environmental factors of grain size sediment and TOM in pre-monsoon period showed a positive and significant correlation. There was no positive and significant correlation with environmental factors in monsoon period (P <0.05), but there was a significant positive correlation with grain size in post-monsoon period (p<0.05). The results showed that winter monsoon causes significant changes in the populations of the studied areas and the increase in density in monsoon can be due to the change of the currents direction and consequent increase of nutrient load in the area.