Neustonic zooplankton in the northeastern Persian Gulf

Abstract

The Persian Gulf is an important area in terms of ecological values and fisheries resources. It also provides a supportive spawning and nursery areas for the finfish and shellfish communities, whose survival depends on the availability of the neustonic zooplankton. Neuston composition, abundance, and distribution were studied during two oceanographic cruises in autumn (Nov. to Dec.) 2012 and summer (Aug.) 2013 aboard R/V Ja Nay Band from 26 stations along the northeast Persian Gulf. Samples were collected in duplicate using a rectangular frame (300μm mesh net). Copepods (including copepodites) were the dominant constituents of the zooplankton and accounted for 56.7% and 69.2% of the total zooneuston populations during autumn and summer cruises, respectively. Among zooneuston, copepod biodiversity was relatively high with thirty-four copepod species in twenty two genera present. The other major groups of zooplankton in term of abundance were fish larvae and eggs 15.2%, urochordates 10.1%, decapods and other crustaceans 6.2%, cladocerans 3.8%, cnidarians 2.7% and chaetognaths 2.4% during the autumn cruise. In contrast, during the summer cruise, the other most abundant zooneuston were urochordates 7.5%, decapods 6.8%, cnidarians 6.1%, chaetognaths 3.8% and fish larva and eggs 1.5%. Zooneuston composition differed slightly in different cruises. Zooneuston abundance was slightly higher during autumn (mean of 295 ± 61 ind. m−3) than summer (231 ± 61 ind. m−3). Total zooneuston abundances were not significantly different (p > 0.05) in both spatial and temporal scales, but their copepod abundances were spatially significant (p < 0.05). Among marine insects, Halobates sp. was the new record for the Persian Gulf.