Environmental Determinants of Zooplankton Community in the Damietta Estuary of the Nile River, Egypt

Zooplankton community and eleven environmental variables were investigated seasonally during 2014 through nine stations in the Damietta estuary of the Nile River. Meroplanktonic larvae were the major component representing 39.4% of the total zooplankton abundance. Copepods and their larval stages contributed 36.2%. Rotifers ranked the third important group (12.6%). Protozoa contributed 10.6% of the total community. According to the Canonical Correspondence Analysis (CCA), the variations in the species data were significantly (P< 0.05) related to salinity, temperature, phosphate concentration and phytoplankton biomass. The main spatial gradients along the estuary were associated with salinity. The high salinity zone in the estuary downstream was dominated by the calanoid paracalanidae and the harpacticoid Euterpina acutifrons. In the lower salinity transects, the tintinnid Favella serrata dominated the estuary midstream, together with several rotifer species in the estuary upstream. The juvenile copepods and the cyclopoid Oithona spp. together with the numerically dominant polychaete and cirriped larvae seemed little affected by salinity gradients.