Abstract: To understand the roles of copepod in the biogeochemical cycling of phosphorus, gut fluorescence method was applied to examine in situ the grazing rate of copepod on the phytoplankton in Xiamen Time Station (XMTS) in May, August and November 2005 and March 2006. In the meanwhile, the abundance and species composition of copepod were investigated, and the grazing pressure of copepod on the phytoplankton was estimated. The results showed that the annual average grazing rate of copepod was 55.53 μg·m^-3·d^-1, being the highest (108.98 μg·m^-3·d^-1) in autumn and the lowest (7.18 μg·m^-3·d^-1) in summer. Based on the estimation from our experimental data, the daily grazing rate of copepod populations on the phytoplankton in Xiamen Harbor was, on annual average, about 181% of the phytoplankton’s standing stock, with the values in spring, summer, autumn, and winter being 3.22%, 0.06%, 3.52% and 0.46%, respectively.

Key words: leaf dry matter, critical nitrogen concentration, maize, nitrogen nutrition index, nitrogen diagnosis