Zooplankton in the Huangyan Atoll, South China Sea: A comparison of community structure between the lagoon and seaward reef slope

Abstract

Relatively few studies have investigated the community structure of zooplankton in the atolls of the central South China Sea. Zooplankton were sampled at nine stations within the lagoon and four facing the seaward reef-slope in the Huangyan Atoll during May 2015. Lagoonal samples contained 48 zooplankton taxa ( H' =2.25±0.95; J =0.70±0.23) with planktonic larvae, copepods, and euphausids contributing 95.63% of total abundance. Seaward oceanic samples contained 114 zooplankton ( H' =5.27±0.27; J =0.90±0.03) with copepods, siphonophores, chaetognaths, appendicularians, and planktonic larvae accounting for 93.66% of abundance. Lagoonal zooplankton abundance was lower than that on the seaward reef-slope. Zooplankton community differed significantly between the lagoon and reef-slope groups ( R =0.708, P =0.001). The former was dominated by Macruran larvae, Brachyuran larvae, Stylocheiron carinatum, and Acartia spp., while the latter was predominately represented by Oikopleura longicauda, Chelophyes contorta and Copilia mirabilis. Chlorophyll a concentration was significantly higher in the lagoon than the reef slope regions ( P <0.01), which may be due to the nutrient input from fishing vessels near the lagoon mouth. Zooplankton abundance was negatively correlated with chlorophyll a concentration ( P <0.01). A clear difference was observed statistically in the species composition and abundance of zooplankton between the lagoon and the seaward slope at Huangyan Atoll, which suggests that it may be resulted from the influence by natural and anthropogenic interactions.