Evaluation of physical and ecological environments of a coral reef and its conservation strategy in a regional environmental system

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1)Performing field surveys for integrated ecosystems comprised of coral reef, seagrass bed, tidal flat and mangroves at Fukido and Todoroki river mouth areas in Ishigaki Is, we have clarified characteristics of currents, related thermal and material transport, coral community metabolism and others. 2)We have developed new optical models for coral and seagrass bed canopies, combined with a nonlinear inverse estimation method, for remote sensing image analyses. With these models, we have succeeded in high-accuracy estimation of coral and seagrass bed canopy height and density and in bathymetry mapping. We have further developed a remote sensing method to detect the coverage of coral reefs by deposited red-soil. 3)Analyzing more than 20 LANDSAT images in the past 20 years at Ishigaki and Iriomote Islands and Sekisei Lagoon in between them, we have found historical change of land-use and vegetation cover of the land areas and its relationship with the inter-annual change of habitat charact … More eristics in the neighboring coral reefs like coral coverage. 4)With a comprehensive field in which we did near-surface particle tracking using small drifters installed with a GPS logger and a mobile phone, HF-radar measurement to detect spatial distribution of ocean surface current, plankton netting at various locations in the wide area concerned, we revealed the inter-reef connectivity in terms of coral larvae dispersal from the Kerama Islands to the west coast of main Okinawa Island. We have developed a multiple-nesting coastal ocean model, in which the computational results of JCOPE model are assimilated, to analyze the flow structure in the coastal areas of the Ryukyu Islands and the larval transport process. With this numerical simulation model we have succeeded in reproducing the eastward current and associated larval transport from the Kerama Islands to the west coast of main Okinawa Island and clarifying the physical mechanism of the generation of the eastward current. We have applied the numerical model further, revealing the inter-reef connectivity in wider regions covering the Ryukyu Islands. 5)To elucidate population dynamics of crow-of-thorns starfish(COTS), which has recently shown outbreaks in the Ryukyu Islands, we have succeeded in developing a larval identification system for wild COTS larvae based on molecular techniques and genetic markers. We have also found peak spawning periods of COTS sampled at five different reefs in the Ryukyu Islands and their dependence on the local water temperature. Less