KINETIC STUDY OF THE DISSOLVED ORGANIC CARBON IN THE XIANGXIBAY, THREE GORGE RESERVOIR REGION DURING THE SPRING BLOOM PERIOD

Daily monitor for the chlorophyll a and dissolved organic carbon (DOC) was carried during the spring phytoplanktonbloom period (22 Feb.,228 Apr., 2005). The aim of this study was to research the kinetic characteristic of DOC during thespring phytoplankton bloom. 300-600mL of water sample was filtered by the micofilter (0. 8μm) for chlorophyll a determinationin the sampling boat using a hand held vacuum pump. And 60mL water sample was passed through a 252mm diameter preashedGF/F filters (450 ℃,4hr) for DOC determination. The DOC was measured using the NPOC methods using total organic carbonanalyzer (Shimadzu,TOC2V). The data of chlorophyll a showed the concentration of chlorophyll a was increased with the lapse oftime, and phytoplankton bloomwas observed twice. The first bloom standing a short period,and the second bloom standing a longperiod. The tendency of the concentration of DOC was similar to the chlorophyll a. Regression analysis showed that theconcentration of DOC could explain 62% of the variability in chlorophyll a concentration in the whole monitoring period(R2 = 0. 62). Considering the rules of the spring bloom, two stages of spring bloom were divided according the dynamics of theconcentration of chlorophyll a: the first stage was ranged from Feb., 23 to Mar.,28., the second stage was ranged from 29Mar., to Apr., 28. Regression analysis for the relationships between DOC and chlorophyll a at different bloom stages was carried out individually. The result showed that the DOC could explain 72% variability in chlorophyll a concentration at the firstbloom stage (R2 = 0. 72), and it could only explain 30% variability in the chlorophyll a concentration at the second bloomstage, According to the main source of the DOC in the natural water body, it can be deduced that the major contribute of DOCmay be produced by the phytoplankton photosynthesis in the first bloom period and the major contribution of DOC may beproduced by the decomposing of died algae in the second bloom period.