碩士 / 國立臺灣海洋大學 / 海洋環境化學與生態研究所 / 102 / In this study, the carbonate parameters around the Dongsha Atoll (DA), including dissolved inorganic carbon (DIC), total alkalinity (TA), pH, partial pressure of CO2 (pCO2) and saturation state of aragonite (a), were thoroughly investigated in June (summer) and December (winter) 2013. The results show that the seagrass-dominant areas, including the small lagoon of the Dongsha Island (DI), and the north and west coasts of the DI, were sinks of atmospheric CO2 in both summer and winter. On the contrary, the coral reef-dominant area, i.e. the DA lagoon, was a source of atmospheric CO2.This difference can be attributed to that photosynthesis is the controlling process in the seagrass-dominant area, which can consume CO2 and thereby make the DI lagoon a sink of atmospheric CO2; meanwhile calcification is the predominant biogeochemical process in the coral reef-dominant area, which can release CO2 and thereby make the DA lagoon a source of atmospheric CO2. The spatial variations of the carbonate parameters around the DI lagoon and the DA lagoon were largely controlled by the coverage of seagrass and coral-reef, respectively. For the DI lagoon, when the seagrass coverage is higher, pCO2 and DIC are lower and pH and a are higher, and vice versa. For the DA lagoon, when coral reef coverage is higher, TA, pH and a are lower, and vice versa. Furthermore, the annual air-sea CO2 exchange flux in the seagrass-dominant areas was estimated to be -8.01±4.18 mmolC m-2 d-1. If the estimated annual CO2 flux is extrapolated to the entire DA seagrass bed, it could take up 288 ton C yr-1 from the atmosphere. This result is lower than the previous estimate of 788 ton C yr-1 based on seagrass productivity measurement. We suggest that this discrepancy may arise from the fact that a fraction of carbon produced by the seagrass were released back into the water column when detritus was decomposed, and thus cause an overestimate for atmospheric CO2 uptake. Finally, we suggest that if high a water in the seagrass-dominant area can flow into the coral reef-dominant area, it may be beneficial for the DA to cope with ocean acidification.
| Identifer | oai:union.ndltd.org:TW/102NTOU5282003 |
| Date | January 2014 |
| Creators | Liu, Ting-Chih, 劉亭之 |
| Contributors | Chou, Wen-Chen, 周文臣 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 44 |
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