Composition, Abundance, and Biomass of Zooplankton Community in Helleh River Estuary, Bushehr, Persian Gulf

Estuaries are one of the most productive aquatic ecosystems that both ecologically and economically are important. In estuarine ecosystems، zooplankton is very important group of animals that they are the basis for food web and intermediate steps in the planktonic food pyramid. Ecological studies، especially temporal and spatial variations of zooplankton are considerable in estuaries. The present study emphasized on zooplankton from Helleh River estuary، Busheher، Persian Gulf that composition، abundance، and biomass of zooplankton communities were investigated together with some of water characteristics. Samples were taken using plankton net with mesh size of 140 µm with vertical towing from 5 fixed-stations in mid-season from summer 2011 to spring 2012 for one year period. The zooplankton comprised of Arthropoda، Annelida، Protozoa، Mollusca، Echinodermata، Chordata، Rotatoria، Nematoda، Ctenophora، and Siphonophora. All samples were dominated by copepods، especially Acartia sp. In addition، Arthropoda had highest abundance while Echinodermata، Rotatoria، Nematoda، Rotatoria، and Ctenophora showed lowest abundance. Of Arthropoda، copepods with 10 genera including; Acartia، Euterpina، Oithona، Oncaea، Paracalanus،Corycaeus، Labidocera، Macrosetella، Microsetella، and Temora were at the highest abundance in zooplankton population. The maximum abundance and biomass was estimated at station estuary mouth (station 5) in all seasons، highest values in autumn (46051. 9 ind. /m3 and 165. 0 mg/m3) and lowest in winter (5388. 4 ind. /m3 and 20. 9 mg/m3). This study may be useful in understanding the ecological and biological processes for sustainable fisheries management in estuaries.