| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 92 === Phosphorus (P) is an essential macronutrient required for all living organisms. Several evidences suggest that phosphorus may limit primary production rates in the oligotrophic marine habitats, which has stimulated great interests in P dynamics. In the ocean, total dissolved phosphorus (TDP) pool, according to the operational definition, is generally partitioned into dissolved inorganic P (DIP, mostly orthophosphate) and dissolved organic P (DOP, mostly phosphorus esters and phosphonates). In this study, a modified alkaline persulfate oxidation method together with standard molybdenum blue method, was examined and employed for quantitatively converting a range of organic phosphorus compounds to orthophosphate, and provided the direct measurements of total dissolved phosphorus in seawater samples.
Field observations of the concentration changes in dissolved phosphorus pool in the South China Sea were made at Station KK1 (18.25°N, 115.67°E) several times from August 2003 to May 2004. Both TDP and DIP concentrations measured in the euphotic zone showed strong seasonal variations and covariant trends with higher concentrations found in summer and winter. The DOP concentrations in the upper 200 m ranged from 0 to 0.3 μM decreasing with depth showed distinct seasonal patterns, and subsurface maximum found in corresponding to that of Chlorophyll-a. As DOP/DIP ratios in the upper 60m showed strong seasonal variations and declined with increasing depth. These results suggest that relatively consistent DOP concentrations in surface water may sustain the nutrient recycling supplying for the growth of living organisms.
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