Spatial distribution of zooplankton in continental slope of northern South China Sea in summer

According to the vertical sampling data on zooplankton in the continental slope of northern South China Sea in summer, 2015, we examined the spatial distribution of species composition, dominant species, abundance, biomass and zooplankton community structure. Zooplankton samples were collected by discrete Multinet at 0~200 m, 200~350 m, 350~450 m, 450~600 m and 600~750 m of depths, respectively. The results show that a total of 468 zooplankton species were found, and the species richness was the highest at 0~200 m layer water, and was the lowest at 600~750 m layer water, but there was slight rebound in some stations at 350~600 m water layer. The zooplankton common species occurring at all water layers took up 19.02% of the total species, while the endemic species occurring at just one water layer made up 25.85% of the total species. There was obvious vertical variation in the zooplankton species composition. A total of 10 dominant species were observed, among which Oncaea conifera was the common species occurring at all water layers. Besides, some endemic dominant species occurred at each water layer. The average abundance and biomass of zooplankton were 62.79 ind·m^-3 and 34.81 mg·m^-3, respectively. With increasing depth of water, zooplankton species richness decreased generally. Three communities were identified by clustering analysis. Group 1 contained samples collected at surface water (0~200 m) with average abundance of 228.68 ind·m^-3. Group 2 contained samples collected at upper-middle-layer water (200~450 m) with average abundance of 31.91 ind·m^-3. Group 3 contained samples collected at lower-middle-layer water (450~750 m) with average abundance of 10.61 ind·m^-3.