| 摘要: | 珊瑚礁是地球上生物多樣性最豐富的生態系之一。在低營養的熱帶海洋中，珊瑚礁因具有相當高的單位總生產力而被稱為熱帶海洋綠洲。珊瑚礁可提供海洋動物遮蔽處、保護海岸、提供漁業、觀光及藥用商業資源。因為珊瑚礁上的流動為運移及傳遞物質的自然營力，所以珊瑚礁的水動力及紊流特性的量化則對珊瑚礁的地質、生物地球化學、生物系統的監測及模擬相當重要。根據最新的文獻整理及計畫主持人最近的研究經驗，波浪作用下淺水區褶狀珊瑚礁內的紊流特性仍有相當大的研究空間。因此，此三年研究計畫將利用野外現地觀測實驗，來探討南台灣南灣後壁湖褶狀珊瑚礁內的紊流、相參結構及多重尺度水動力的交互作用。為了量測較大的紊流相參結構並解析相關物理量的空間梯度，研發全域瞬時速度量測的新式儀器顯得刻不容緩。因此，本計畫第一年將發展一個具大視窗速度量測的水下質點影像測速儀。另外，在第一年的計畫裡也規劃了小型現場試驗來測試此系統，並量測部分資料以供分析。第二年計畫規劃了較為大型及長期的現場實驗來量測包含平均流、環流、波浪能通量、消散率、紊流等大小不同尺度的水動力物理量。第三年計畫則會將此測速儀移至此珊瑚礁的不同位置來觀測局部地形對周圍紊流特性的影響。相關的資料分析也將預期在各年度研究規劃中完成。由現地實驗量測及資料分析，本計畫擬將探討以下幾個科學的問題：南灣後壁湖褶狀珊瑚礁的多重尺度水動力過程、此珊瑚礁內的流動驅使機制、不同尺度流動的交互作用、波浪消散機制、波浪相位相關的紊流特性、碎波對珊瑚礁邊界層的影響、珊瑚礁群聚對紊流空間分佈的影響、流動與多重尺度地形的作用機制、紊亂漩渦及相參結構特性、紊流傳遞機制等相關問題。有了國科會的經費支持，這個計畫的成功指日可待。本計畫對珊瑚礁內多重尺度的水動力、紊流及相參結構的研究成果，可作為日後研究此褶狀珊瑚礁內營養鹽攝取及幼子分佈及附著的前期研究。 Coral reefs are one of the most biologically diverse ecosystems on earth; they have high areal gross productivity in the very low nutrient waters of tropical seas so that they are reputed as “oasis in the desert” in tropical marine environments. They provide shelters for ocean animals, protect coastline, and support commercial fisheries, tourism, and medicinal benefits. Since flows are the natural forces to drive and disperse materials over the reefs, quantification of hydrodynamics and turbulent flow properties of coral reefs is crucial for modeling and monitoring geological, biogeochemical, and biological systems over coral reefs. Based on the updated literature review and the PI’s recent research experiences, turbulent properties over shallow fringing coal reefs exposed under waves are largely unexplored. The present three-year research project is therefore prompted to conduct in-situ field observations of turbulence, coherent structure, and interaction between multi-scale hydrodynamics over the fringing coral reefs at Hobihu, Nan-Wan Bay, southern Taiwan. To measure large coherent turbulent structures and resolve spatial gradient of related physical quantities, there is a clear need of developing a novel instrumentation to measure the full map of instantaneous turbulent flow velocities; consequently, the high field-of-view submersible PIV (SPIV) system will be developed in the project. In addition, a small-scale field experiment is planned to be conducted in the first year to test the performance of the SPIV system and to sample some data for analysis. A large-scale experiment is scheduled in the second year to measure the multi-scale hydrodynamics of current, circulation, wave energy flux, dissipation rate and turbulence over the fringing coral reefs. In the third year, the SPIV system will be moved to other locations in the fringing reefs to examine the effects of the local topography on ambient turbulence. Related data analysis will be carried out in the proposed research years. Through the in situ experiments, measurements, and data analysis, several scientific questions this project is seeking to investigate include: the multi-scale hydrodynamic process, mechanism driving the flow over the fringing reefs, interaction of multi-scale flow motions, wave dissipation mechanism, wave-phase dependent turbulent quantities, effects of wave-breaking generated turbulence on the boundary layer flow over fringing reefs, effects of reef community on spatial distributions of turbulent quantities, mechanism of the driven flow interacting with multi-scale reef topography, the properties of turbulent eddies and coherent structures, and mechanism of turbulent transport in the shallow water fringing coral reefs at Hobihu, Nan-Wan Bay, southern Taiwan. With the financial supports from NSC, we may expect the success of the project. The progress of the proposed project on the multi-scale hydrodynamics, coherent structure, and turbulence over coral reefs will provide useful knowledge for further study of their effects on nutrient uptake and larvae distribution and settlement in coral reefs. 研究期間：10008 ~ 10107 |
