Size-based analysis of a zooplankton community under the influence of the Pearl River plume and coastal upwelling in the northeastern South China Sea

摘要

To examine zooplankton responses to the Pearl River plume (PRP) and coastal upwelling on the northern shelf of the South China Sea (SCS), zooplankton (>160 mu m) were investigated in the northeastern SCS during 30 June to 11 July 2008. Zooplankton biomass size spectra (BSS) were constructed to describe zooplankton communities. The BSS parameters such as intercept and slope values were 8.659 +/- 0.727 and -0.816 +/- 0.074, respectively. On the basis of the BSS parameters, the sampling sites were classified into two main groups, which corresponded to the plume- and upwelling-affected areas, respectively. In addition, a positive correlation between zooplankton and phytoplankton abundance (P < 0.05) was observed in the study waters. These results indicate that (1) zooplankton BSS could be used as an indicator for distinguishing the physical processes, and (2) the PRP and coastal upwelling could regulate zooplankton communities differently through altering nutrient supply for the phytoplankton. The BSS slopes were flatter than expected for a steady-state community and the dominance of jellyfish in the larger size fractions indicated that an energy accumulation in gelatinous organisms occurred in the study waters. Since gelatinous organisms are not food for fish, this energy accumulation may be detrimental to the fishery production in the study area.