碩士 / 國立中興大學 / 生命科學系所 / 105 / Methane seeps occur at the passive continental margins around the world. These seepages not only embrace abundant gas-hydrate resources but also nurture massive chemoautotrophic or chemosymbiotic species. The chemoautotrophic/symbiotic species could use the energy directly from the gas-hydrate and then transfer them to other associated seep or non-seep fauna. Consequently, seepages become the hotspots of biomass and biodiversity in deep-sea. In order to establish the baseline of the biological resources before the gas-hydrate resources mining, and assess the impacts of exploitation on deep-sea ecosystems, we collected biological environmental data from the northern continental slope of South China Sea in eight research cruises between 2013 and 2016. In addition to estimate the local/regional biodiversity, we investigated the community of megabenthos as well as their relationships with environmental factors. Furthermore, we used the ratios of δ13C and δ15N stable isotopes to trace the food sources of the heterotrophic consumers, to estimate the trophic contributions of the methane seep, and to compare the trophic niches of the seep and non-seep communities. For studying the pathways of energy flows and revealing the importance of methane seeps in the deep sea, the Ecopath models of the seep and its surrounding ecosystems were constructed. Finally, we utilized the temporal module Ecosim to simulate the potential distutbances of the seep and peripheral ecosystems after commercial mining for gas-hydrates. The results showed that both the species diversity and evenness were very high in spite of low nutrition on the continental slopes. Moreover, both these suspensivores and depositivores preferred to inhabit places where had relatively more food. The results of stable isotope analysis illustrated 4-5 trophic levels in the deep-sea ecosystems we sampled. Large benthic fish and lithodid crab ever entered into the sites of methane seeps and exported the methane-derived carbon to surroundings. On the other hand, both the trophic diversity and isotopic niche widths of the seep community were greater than non-seep community. However, the niches of seep and non-seep communities did not overlap. The results of network analysis indicated that energy flows were greater in the deep-sea ecosystem with seep rather than without seep because of the higher productivity and biomass. The indices of information theory displayed that the deep-sea ecosystem without seep was more stable, nevertheless, the deep-sea ecosystem with seep had higher resilience after the disturbance. According to the Ecopath models from Ecosim without considering area sizes and infauna of the methane seeps, if the reduction in the biomass of seep mussels is less than 50% within the 10 years after gas hydrates mining, there will be no obvious impact on the total energy flows of the system, the biomass of seep and other deep-sea groups, and community structure. In conclution, the intermediate disturbance of mining can increase the maturity level and the geometric mean trophic transfer efficiency at the same time in the modeling ecosystem.
| Identifer | oai:union.ndltd.org:TW/105NCHU5105053 |
| Date | January 2017 |
| Creators | Zhe-Yu Lin, 林哲宇 |
| Contributors | Hsing-Juh Lin, Hsuan-Wien Chen, 林幸助, 陳宣汶 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 196 |
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