Species composition and grazing of microzooplankton in central South China Sea in autumn of 2016

To understand the species composition and grazing of microzooplankton in the central South China Sea (CSCS), we collected the surface water at ten sites in CSCS in October, 2016, and analyzed the abundance and species composition of their microzooplankton, as well as estimated the growth rate of phytoplankton and grazing pressure of microzooplankton on phytoplankton by dilution technique. A total of 21 microzooplankton species were identified, and the microzooplankton abundance varied from 120 ind·L^–1 to 1 300 ind·L^–1. The mean values of phytoplankton growth rate and microzooplankton grazing rate were – 0.92 –1.16 d^–1 and 0.17 –1.58 d^–1, respectively. Compared with the results of other sea areas in China, the grazing pressure of microzooplankton in CSCS was at a medium level. The mean values of grazing pressure on phytoplankton standing crop and grazing pressure on primary production were 15.6% –79.4% and –593.2% –187.7%, respectively. The grazing pressure on the primary productivity at most stations was over 100%, indicating that microzooplankton has obvious inhibitory effect on the growth of phytoplankton and plays an important role in primary production and secondary production of energy transfer process in CSCS.