Onshore–offshore variations of copepod community in northern South China Sea
2009
Zhang, Wuchang | Tang, DanLing | Yang, Bo | Gao, Shangwu | Sun, Jun | Tao, Zhencheng | Sun, Song | Ning, Xiuren
Copepod communities in onshore and offshore waters show a gradient from primarily near shore to primarily oceanic species. Understanding the transition between these communities is fundamental to determining the range of coastal influence. Copepod communities in the northern South China Sea (nSCS) were studied based on samples collected by vertically towing a net in 10 February–6 March (winter) and 26 August–6 September (summer) of 2004. Calanoida species richness, total copepod abundance, Shannon–Weaver diversity index, and onshore–offshore occurrence of dominant species showed obvious change from onshore to offshore waters. Although the offshore stations had lower abundance than the shelf stations, they had more species and larger diversity index. Abundance of some species (groups) with dominance index >5% (Calanus sinicus, Euchaeta spp., Temora spp., Paracalanus parvus, and Subeucalanus subtenuis) declined from onshore to offshore waters. Warm water species (Pleuromamma abdominalis, P. gracilis, and P. robusta) occurred in offshore waters in both cruises. Station (q-type) cluster analysis in winter and summer separated copepod community into onshore and offshore communities at ~40% level of similarity. The two communities were divided at the position of ~100-m isobath. In summer, C. sinicus occurred in the upwelling area east of Hainan Island, indicating the presence of an oversummering stock of this species.
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