Hydrographic characteristics and community structure of epipelagic mesozooplankton in the Dongsha (Pratas) Atoll, South China Sea

Abstract

The relationship between hydrographic features and the community structure of epipelagic mesozooplankton was examined among 10 stations of the water body within the Dongsha (Pratas) Atoll during April (spring), July (summer) and October (autumn) 2011. The hydrographic conditions of the Dongsha Atoll were likely influenced by air temperature and rainfall due to the semi-enclosed topography. Surface water was warm and less saline, particularly in autumn, apparently due to the passage of Typhoon Nalgae. The highest mean (±s.d.) abundance of mesozooplankton was recorded in spring (1204 ± 336individualsm–3) and the lowest was recorded in autumn (45 ± 9individualsm–3). Twenty-six major mesozooplankton groups were observed across the samples collected. Mesozooplankton communities were dominated by calanoid copepods, crab zoea, fish eggs and foraminiferans, which together comprised 86.01% of the total zooplankton catch. The absence of significant correlation between mesozooplankton abundance and chlorophyll-a concentration indicated that the temporal pattern of the mesozooplankton community seems to be more dependent on physical variables than on primary production.