Intrusions of the Kuroshio Current in the northern South China sea affect Copepod assemblages of the Luzon Strait

Abstract

We analyse the influence of the Kuroshio Current on copepod assemblages in the northern South China Sea. The assumption was tested whether predominant current regimes bring marine zooplankton and Copepoda from subtropical and tropical waters to the south of Taiwan. A total of 101 copepod species were identified from 26 families and 48 genera that include Calanoida, Cyclopoida, Harpacticoida and Poecilostomatoida. High copepod abundances in the study area are shown to be caused by both, a year-round Kuroshio Current intrusion and the SW monsoon, prevailing in the South China Sea during summer. Calanus sinicus did not appear in the samples, indicating that there was no cold water mass intrusion in the area during sampling. Both, the intrusion of the Kuroshio Branch Current to the Luzon Strait and the South China Sea circulation may play a more important role in shaping copepod assemblages in the region than hitherto expected. The abundance of copepods was higher above the 50 m isoline than at deeper strata. Species number and the Shannon–Wiener diversity index were higher with increasing depth. Copepod assemblage structure changed with different sampling depth and different sampling areas. Copepod abundance and species richness were higher in the northern South China Sea than in the Kuroshio Current area, and higher at lower latitudes than at higher latitudes. Some indicator species are characteristic for the Kuroshio Current and indicate with others that the study area accomodated water masses from the northern South China Sea as well as from the Kuroshio Current.