Spatiotemporal fluctuations in surface copepods community structure in Chabahar Bay, Gulf of Oman, Iran

In the present study, the spatiotemporal distribution and community structure of surface copepods were investigated in Chabahar Bay, Gulf of Oman, through a year-long sampling programme divided into four distinct periods: post-monsoon (POM), northeast monsoon, pre-monsoon (PRM), and southwest monsoon (SWM). Sampling was conducted at five locations using a horizontal plankton net with a 100 μm mesh size, from the midnight to dawn period. Environmental parameters (temperature, salinity, pH, and total dissolved solids) were also recorded, revealing significant differences (P < 0.0005) across seasons and locations. A total of 38 copepod genera, belonging to five orders and 22 families, were identified, accounting for 66% of the total zooplankton population, while the remaining 34% consisted of non-copepod organisms. The highest and lowest mean abundances of copepods were recorded during the PRM and POM periods, respectively. Excluding copepod larvae, Cyclopoida and Calanoida exhibited the highest annual mean abundances, while Monstrilloida had the lowest. Results show the highest annual mean abundance belongs to the genera Oithona with 167,382 ± 11,089 ind. m−3, Temora with 52,250 ± 3691 ind. m−3, Paracalanus with 40,041 ± 2256 ind. m−3, Acartia with 34,822 ± 3876 ind. m−3, Euterpina with 34,313 ± 1542 ind. m−3, and Oncea with 34,033 ± 2951 ind. m−3. However, the lowest value of 794 ± 259 ind. m−3 belonged to the genus Cymbasoma. The highest mean diversity index (H′) was observed in SWM and POM, while the highest mean species richness index (D) was observed in POM and SWM, and the highest mean Pielou's evenness (J′) was observed in SWM and POM.