Fig.2 Maps and hydrographical properties of studied areas in the epipelagic waters of China marginal seas in summer-autumn.Maps of sampling sites (a); hydrographical properties of temperature and salinity (b) of different water masses that were identified based on the Supplementary Methods and were displayed in different colors in the left map (a); environmental variations of samples from different water masses displayed by principal component analysis (PCA) (c). The bottom layer in the SCS represents the bottom of the photic zone. The abbreviations of the water masses are: Mc , Minzhe coastal water; Cm , Coastal mixed water; Zd , Zhujiang River diluted water; Es , East China Sea surface water;Km , Kuroshio surface-subsurface mixed water; Ss , South China Sea surface water; Sm , South China Sea surface-subsurface mixed water; Ss-2017 , South China Sea surface water of 2017;Su-2017 , South China Sea subsurface water of 2017;Pu-2017 , Pacific Ocean subsurface water of 2017. According to the salinity and the distance from the shore of the water masses, the Mc and Zd were considered as coastal waters, the Cm, Es, and Ss were considered as mixed waters, while the Km, Sm, Ss-2017, Su-2017, and Pu-2017 were assorted to oceanic waters. The abbreviations of the environmental variables are: Temp, temperature; Sal, salinity; DO, dissolved oxygen; Fluo, fluorescence; SiO3-Si, Silicate.