SIZE-FRACTIONATED PRODUCTIVITY AND NUTRIENT DYNAMICS OF PHYTOPLANKTONIN SUBTROPICAL COASTAL ENVIRONMENTS

It is now well established that the size distribution of phytoplankton plays an important role in primary production processes and nutrient dynamics of coastal environment. In situ observations showed that nano phytoplankton (3 similar to 20 mu m) contributed 72.08% and 58.18% of phytoplankton biomass and 58.32% and 41.14% of primary productivity to Xiamen Western Waters and the northern Taiwan Strait, respectively; p icophytoplankton (0.2 similar to 3 mu m) dominated the biomass (64.70% ) and productivity (66.09%) in the southern Taiwan Strait. Furthermore , nanophytoplankton accounted for 75% of phosphate uptake with the hig hest rate constant (8.3 x 10(-5) s(-1)) and uptake rate in unit water volume (5.4 x 10(-5) mmol dm(-3) s(-1)); picophytoplankton had the hig hest uptake rate in unit biomass (5.4 x 10(-5) mmol mg(-1) s(-1)) and photosynthetic index (3.8 mgC mgChl a(-1) h(-1)). All the results high lighted the remarkable characteristics of small size ranged (0.2 simil ar to 20 mu m) phytoplankton in subtropical coastal environments: main contributor to phytoplankton biomass and production, high efficiency on organic carbon production and nutrient recycling. The far reaching environmental and ecological implications were discussed.