Radiolarian assemblage as an indicator of environmental conditions in the marginal seas of the Western North Pacific

In this study, we analyzed 45 surface sediment samples collected in the marginal seas of the Western North Pacific, including the South China Sea, the East China Sea, and the Philippine Sea, to investigate the radiolarian assemblages and their relationship with upper layer environmental conditions. Based on the results of Q-mode cluster analysis, the radiolarian assemblages can be divided into four clusters, corresponding to the North Equatorial Current assemblage, North Equatorial Current Bifurcation assemblage, Kuroshio-South China Sea assemblage, and Kuroshio-East China Sea assemblage. Winter sea surface temperature (SSTw), winter sea surface salinity (SSSw), and annual silicate concentration were the most significant environmental variables associated with the radiolarian assemblages, among which SSTw showed the highest correlation with the radiolarian fauna. The significant influences of SSTw and SSSw suggested that the seasonal change of the North Equatorial Current-Kuroshio Current system exerted a crucial effect on the abundance and distribution pattern of the radiolarian fauna.