Community structure of Thaliacea in the Zhongsha and Xisha Islands sea areas of the South China Sea

Based on the four seasonal investigation data collected from the Zhongsha and Xisha Islands, South China Sea (1230N～ 1732N,11000N～11011N) during 2014～2015, we investigated the characteristics of thaliacean community. Twenty-three species were catched (16 in summer, 15 in winter, 14 in spring and 10 in autumn). According to the result of alternation fraction (R), the seasonal alternation of the species between winter and the other seasons was more obvious. The average abundance was 0.99 indm-3 ( 1.93 indm-3 in summer, 1.12 indm -3 in winter and 0.32 indm-3 in autumn). Doliolum denticulatum and Thalia democratica in four seasons and Pyrosoma atlanticum in spring and summer were dominant in abundance distribution. The dominant species clustering led to normal diversity. The results of MDS show no obvious change in thaliacean community structures among seasons. The distributi on of thal iacean is highly related with surface currents.