Luzon Strait is the deepest channel for water exchange between the Northern South China Sea (NSCS) and the West Philippine Sea (WPS). It is important to investigate the seasonal and spatial distributions and the biogeochemical processes of organic carbon, nitrogen and phosphorus in Luzon Strait. During the summer season, the flow of Kuroshio water into the SCS through the Bashi Channel was restricted due to the prevailing southwest monsoon. However, during the winter season, the flow of Kuroshio water into the SCS through the Bashi Channel was enhanced due to the prevailing northeast monsoon. The characteristics of water types across the Bashi Channel depend highly upon the water exchange between the WPS and the NSCS.
Distributions of dissolved organic carbon (DON), nitrogen (DON) and phosphorus (DOP) in the euphotic zone generally show an increasing trend from the WPS to the NSCS. The same distribution was pattern found for particulate organic carbon (POC) and nitrogen (PN). The stichomythic ratio (C/N/P) of dissolved organic matter in the euphotic layer was lower in spring than in autumn. The reason may be that the Kuroshio water flowing through the Luzon Strait is much less in spring than in autumn. The ratios of DIN/DIP were much lower than the Redfield ratio (16) suggesting a status of N-limitation in the euphotic zone. The DOC/DON ratios, however, were much higher than the Redfield ratio (6.6). These results implied that DOM might have played an important role in modulating nutrient cycling and food web dynamics in the euphotic zone of study area. The subsurface water (100-600m) of the NSCS, west of Luzon, was more enriched with POM than that of the WPS. However, the situation was reversed in the intermediate water (600-1500m). Correlations are significant between POC and Chl-a in spring and summer, suggesting that phytoplankton abundance may primarily control the distribution of POC in the euphotic zone. The DOC/POC ratio was inversely correlated with Chl-a in both spring and summer. The ratios generally decreased to a constant value as the Chl-a concentration increased to a higher level, implying a higher biological contribution for POC than for DOC. Correlations were also significant between TEP/POC and Chl-a. The ratio of TEP-C/POC in the euphotic layer showed a decreasing trend from the NSCS to the WPS, implying a significant influence of phytoplankton productivity on TEP distribution.
During the study period, the integrated gross production (IGP) and integrated dark community respiration (IDCR) in the study area were in the range of 3056~7094 mg C m-2 d-1 and 3372~8901 mg C m-2 d-1 in autumn, respectively; 1740~5338 mg C m-2 d-1 and 2628~7685 mg C m-2 d-1 in spring, respectively; 2149~6110 mg C m-2 d-1 and 4391~8896 mg C m-2 d-1 in summer, respectively. During the autumn and summer season, there were no significant correlations between GP (DCR) and temperature, PAR, salinity, Chl-a, DOC and POC, possibly resented from the effect of typhoon. During the spring season without the typhoon effect, there were significant correlations between GP (DCR) and salinity, Chl-a, DOC and POC. The ratio of IGP/IDCR is an indicator of net ecosystem production, with>1 for the autotrophic system and <1 for the heterotrophic system. The ratio was <1 for all stations indicating a heterotrophic system. However, the ratio was slightly higher in autumn than in spring and summer.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0911106-155949 |
| Date | 11 September 2006 |
| Creators | Hsiang, Chin-Ying |
| Contributors | Jia-Jang Hung, Yu-Chia Chung, Yuh-ling Lee Chen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0911106-155949 |
| Rights | off_campus_withheld, Copyright information available at source archive |
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