Geospatial variability in the autumn community structure of epipelagic zooplankton in the upper layer of the northern South China Sea

Abstract

Background For the present study, we collected mesozooplankton in the upper layer (above 100 m in depth) of four stations in the northern South China Sea (SCS) to determine the influence of different water masses on their distribution and abundance from 27 September to 2 October 1999.

Results In total, 18 major zooplankton taxa were recovered from the samples. Calanoid copepods, Noctilucales, and chaetognaths were dominant and together comprised 65.90% of the overall zooplankton counts. Zooplankton densities ranged from 102.19 to 1,285.24 individuals per cubic meters (ind./m3) (average, 306.38 ± 435.71). Noctilucales were abundant at stations located in the Kuroshio Current (KC) intrusion area. Integrating all samples, 32 copepod species were identified consisting of 23 genera belonging to 16 families. Total copepod abundances ranged from 30.24 to 311.17 ind./m3 (average, 99.14 ± 97.84). Numerically, Pleuromamma gracilis, Nannocalanus minor, and Lucicutia flavicornis were the most dominant species. The most frequently occurring species in all samples were Acartia (Acartia) negligens and Corycaeus (Farranula) gibbula. Results of a cluster analysis indicated that community structures of zooplankton and copepods of the northern SCS varied at geospatial scales during the sampling period.

Conclusions Results of the present study suggest that the composition and community structure of zooplankton and copepods were influenced by intrusion of the KC in the shallow layer above 100 m in depth in the northern SCS. Some indicator species characteristic of the KC indicated that the study area received water masses from the northern SCS and the KC.