Polychaeta density changes in Chabahar Bay subtidal area with emphasis on the role of heavy metals (Cooper and Zinc)

Chabahar Bay near Makran Sea, with the ports of transactions, has always been under the influence of annual monsoon the Indian Ocean. Density changes and heavy metals copper and zinc of Chabahar bay subtidal sediments were studied in 22 stations and three seasons that include: pre-monsoon, monsoon and post-monsoon during 2014. Polychaeta abundances mean were for premonsoon  1261.49±38.81, monsoon 513.81±65.6, postmonsoon 630.45± 73.84 ind/m2 that significant difference was observed between stations and seasons (p<0.05). Metals copper and zinc had fluctuations in three seasons, but despite the significant differences between the stations, there was no significant difference between seasons. Metals mean in preM, M, postM respectively for Cu include 19.89±3.34,14.42±4.47,12.9±3.4 and for Zn 73.42±5.51, 66.04±6.37, 61.72±4.86 µg/g dry weight that only in three stations and only in Cu, concentrations were higher than ERL but in total Chabahar bay metal mean were lower than ERL. Significance correlations were not observed between Polychaeta density and heavy metals except for copper in pre-monsoon. The results showed the impact of monsoon currents in the distribution pattern of polychaete and heavy metals and also were no significant differences in the relationship between density and concentration of can be as results of the low concentration heavy metals in sediments of international standards and other environmental factors on polychaeta density.