Dynamics of DOC of euphotic layer in the Taiwan Strait——Diurnal variation of large range

Three oceanographic investigations from 1994 to 1995 in the Taiwan Strait show that the dissolved organic carbon in the euphoric layer has.large-scale diurnal variation[2-4 mg/dm³],and its amplitude range has spatial and seasonal changes.Generally,the DOC in the euphotic layer is higher at day than that at night.According to the diurnal variations,DOC can be divided into two parts:new DOC and old DOC.The content of new DOC varies rapidly every day but the content of old does not.Though there is still not a good explanation for this diurnal variation of DOC,it may call attention to the study of organic carbon dynamics,especially the DOC primary production of phytoplankton,the DOC utilization of bacteria,and the flux of DOC in coastal sea water.