| Summary: | 碩士 === 國立中山大學 === 海洋地質及化學研究所 === 89 === Abstract
The South China Sea (SCS) is the largest marginal sea in the world and connects with the East China Sea (ECS) through the Taiwan Strait (TS). This study investigates the distribution and biogeochemical behavior of both particulate and dissolved organic matter in the SCS and the TS based on samples collected on several cruises of the R/V Ocean Researchers I and III. Dissolved inorganic nitrogen and phosphorus (DIN and DIP), particulate organic carbon and nitrogen (POC and PON) as well as dissolved organic nitrogen and phosphorus (DON and DOP) concentrations were determined. Concentrations of DON and DOP in the SCS are in the range of 1.2-9.9 mMN and 0.04-0.21 mMP, respectively. The surface DON concentration is the highest in the northern SCS, whereas it is the lowest in the southern part. The DOP does not show a similar trend. DON and DOP concentrations all decrease with depth but increase slightly near the bottom, perhaps on account of sediment resuspension. Because of the preferential degradation of DOP over DON, the maximum concentration of DOP appears at a shallower depth than that of DON. Approximately 11 % and 2 % of DIN and DIP respectively are attributed to the degradation of DON and DOP above 500 m in the SCS. Concentrations of POC and PON in the SCS are in the range of 1.06-2.84 mMC and 0.07-0.36 mMN, respectively. The distributions of POC and PON show similar patterns with a correlation coefficient of 0.97. The concentrations of these are the highest at the surface layer, decrease with depth, but then increase slightly near the bottom, perhaps again because of resuspension of the bottom sediments. The ratio of PON/POC is 0.138 in the euphotic zone, a value close to the Redfield ratio of 0.15.
In the TS and the adjacent coastal zones, the effect of terrestrial input is obvious and results in higher POC, PON, DON and DOP nearshore. Ranges of these concentrations are 0.06-59.6 mMN, 0.01-1.29 mMP, 3.80-57.1 mMC and 0.19-3.4 mMN, respectively.
There was an attempt to use the one-dimensional diffusion-advection model to estimate the DIN and DIP production rates and the DON and DOP consumption rates over the depth range of 900-2500 m. These values are, respectively, 0.036, 0.006, 0.021 and 0.002 mmol/kg/yr.
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