The study of seasonal distribution and density of zooplankton in the northern coast of the Makoran Sea

The purpose of this study was to investigate the zooplankton population of eastern coasts of Chabahar and northern Makran Sea during 2017-18. Sampling was carried out using a 100 μm mesh Zooplankton cone net with a 30 cm opening diameter in horizontal span at 8 stations in Chabahar, Beris and Rimini Bay during four seasons from summer 2017 to spring 2018. Physicochemical properties of water were measured including temperature, salinity, pH and transparency at each sampling station. According to one-way ANOVA, there were no significant differences between the different seasons in transparency (p> 0.05). Significant differences were observed for the temperature, salinity and pH factors between the different sampling seasons (p <0.05). In this study, 10 classes of zooplanktons were identified. The Copepoda accounted for 66.87% of the zooplankton population followed by Bivalves (7.53%), Thaliacea (6%), and Polychaeta, Cephalochordata, Ostracoda (2.22%). The minimum zooplankton density was observed in winter with an average of 876.52 ± 41.62 individuals per cubic meter of water and the maximum density in autumn with an average of 1339.93 ±41.16 individuals per cubic meter of water. Also, a significant positive correlation was observed between zooplankton density and temperature (r= 0.628, p = 0.0001) or salinity (r=0.391, p = 0.027). According to the results, the structure of zooplankton communities in this region seems to be influenced by the changes caused by monsoon winds and coastal currents. Thus the production cycle and seasonal fluctuations of zooplankton depend on the response the environment exhibit to these changes. As a result, when zooplankton are exposed to severe disturbance (monsoon), several species become dominant species and reduce species homogeneity.