碩士 / 國立臺灣海洋大學 / 海洋環境與生態研究所 / 105 / Since the beginning of the industrial era, atmospheric CO2 concentration has
increased at a rate unprecedented for hundred millions of years. More than one quarter
of anthropogenic CO2 emissions have already been absorbed into the oceans, driving
down ocean pH, a process known as ocean acidification. Such striking changes in ocean
chemistry could have serious impacts on marine ecosystems, especially for those
dominated by calcifying organisms. Rooted in the assumption that reef-water pH tracks
open-ocean pH, global-scale predictions show that coral reef calcification could
decrease by 17–35% by 2100. However, due to strong metabolism in reefs, the pH of
water bathing corals may not respond proportionally to the pH of the open ocean. A
better understanding on the processes controlling community metabolism and its
influence on carbon chemistry of seawater is, therefore, required to accurately predict
the future changes of coral reefs. In this study, the carbonate parameters around
Dongsha Atoll (DA), including dissolved inorganic carbon (DIC), total alkalinity (TA),
pH, partial pressure of CO2 (pCO2), saturation state of aragonite (Ωara), salinity and
temperature were thoroughly investigated in August 2015 and 2016. The results show
that temperature at the northeast part of lagoon is the highest, while temperature at the
north and the south channels is much lower, suggesting a relatively long residence time
for the water in the lagoon. Evaporation, rainfall and various metabolic reactions have
significantly modified the carbon chemistry of seawater in the interior of lagoon. pCO2
in the lagoon was significantly higher than that in the outer atoll in both years. pCO2 in
the lagoon shows a clear annual variation: pCO2 in 2016 (542±101 μatm) was higher
than that in 2015 (447±41 μatm). The highest pCO2 was found in the central part of
lagoon in 2016, which corresponds well to the lowest pH and TA values, suggesting
that the high pCO2 may be caused by stronger calcification. Using the net changes of
TA and DIC between the entrance and the interior of lagoon, organic carbon and
inorganic carbon metabolism was estimated. The estimation shows that in terms of
organic carbon metabolism, the northern and southern part of lagoon in 2015 and the
central and southern part of lagoon in 2016 was dominated by respiration, while the
northeastern part of lagoon was dominated by photosynthesis in both 2015 and 2016.
In terms of carbonate metabolism, the entire lagoon is dominated by calcification in
both years. Because both calcification and respiration would release CO2, thereby
driving the lagoon acting as a strong CO2 source. Also, the spatial variations of pCO2,
pH, andΩara can be well explained by the analysis of organic carbon and inorganic
carbon metabolism in DA.
| Identifer | oai:union.ndltd.org:TW/105NTOU528A005 |
| Date | January 2017 |
| Creators | Qiu, Song-Quan, 邱松權 |
| 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 | 48 |
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