Community characteristics of pelagic copepods in Nansha area before and after onset of Southwest Monsoon

According to the oceanographic surveys on zooplankton in Nansha area before and after the onset of Southwest Monsoon ( OSM) duringMarch～April and June ～July in 2013, we investigated the species composition, abundance, ecological groups, dominant species and diversity of the pelagic copepods. A total of 187 copepod species were identified, including 127 macro-copepod species and 152 meso-copepod species. The fauna of copepods belonged to the typical tropical ocean region with four ecological groups, such as oceanic species, euryhaline species, neritic species and deep-water species. The dominant species of the macro-copepods changed unobtrusively and those of the meso-copepods changed significantly with OSMtransformation. The average macro-copepods abundance was 4.87 indm-3 , about a quarter of the average meso-copepods abundance of 19.2 indm-3 . The copepod diversity was rich or very rich. The horizontal distributions of the copepod community characteristics changed along with the surface currents and water masses by OSMtransformation, and macro-copepods were more sensitive to the vertical movement of the water masses but duller to the change of the surface currents than meso-copepods.