1Department of Natural Resources, Isfahan University of Technology, Isfahan, Iran
2Persian Gulf Research Institute, Persian Gulf University, Bushehr, Iran
Copepods are the main zooplankton assemblages in most tropical and semi-tropical estuaries. In this research, copepod population dynamics were investigated in Helleh River estuary, Persian Gulf during four seasons beginning from summer 2011 to spring 2012. Samples were taken using plankton net with mesh size of 140 µm and vertical towing from 5 fixed-stations in mid-season. Results showed that copepod comprised 10 families viz. Acartiidae, Paracalanidae, Pontellidae, Temoridae, Oithonidae, Oncaeidae, Corycaeidae, Euterpinidae, Ectinosomatidae, and Miraciidae and 10 genera viz., Acartia, Paracalanus, Labidocera, Temora, Oithona, Oncaea, Corycaeus, Euterpina, Microsetella, and Macrosetella. The most dominant copepod was Acartia sp., with the highest abundance in the fall (36068.3 ind./m3) and the lowest in the winter (1857.3 ind./m3). Diversity was the highest in the summer and the lowest in the winter. There were significant correlations (P<0.01) between copepod abundance as well as biodiversity with salinity and dissolved oxygen. Based on this study, the most important factors in mudflat shallow river–estuarine system that can describe most changes of copepod assemblages were salinity, dissolved oxygen, chlorophyll a, temperature and Secchi depth, respectively. The cluster analysis aggregated the community into two groups, one associated with nauplii copepod and the other with copepodids and adults.