| 研究実績の概要 |
An improved version of the lightweight autonomous underwater vehicle (AUV) HATTORI (Highly Agile Terrain Tracker for Ocean Research and Investigation) was built by Prof. Toshihiro Maki’s laboratory (Institute of Industrial Science, The University of Tokyo) in collaboration with FullDepth Co., Ltd. This new AUV (HATTORI 2), like its predecessor (HATTORI 1), is equipped with high-resolution video cameras and designed to take video images of the seafloor while following a pre-programmed path at a specified and constant elevation. HATTORI 2 can travel back and forth and therefore can map wider areas of seafloor compared with the previous model which could only travel in one direction. Moreover HATTORI 2 is equipped with a super short baseline acoustic system (SSBL) to determine its position relative to the ship during each dive. The new AUV HATTORI 2 was successfully tested in November 2018 at three sites around the Sekisei Lagoon, southern Ryukyu Islands. In addition, to further constrain the nature and distribution of marine organisms and sediments at mesophotic depths around the Sekisei Lagoon, two remotely operated vehicles (BlueRov 2, Blue Robotics Inc., and FullDepth DiveUnit 300, FullDepth Co., Ltd.) were deployed at six sites, including the two sites surveyed by the AUV at depths of 30-65 m along the outer margin of the Sekisei Lagoon and comprise 4 sites which, to the knowledge of the author, have never been explored previously. A total of ten sediment grab samples were also collected at the surveyed sites to verify the nature of bottom sediments.
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| 今後の研究の推進方策 |
The next phase of this research project will focus on the study of fossil coral assemblages in cores drilled at multiple locations in the Ryukyu Islands by the ICDP COREF project. There is a total of 11 cores targeted for this research, taken from three islands, in the south (Yonaguni-jima) and central (Okinawa-jima and Kodakara-jima) Ryukyu Islands. These cores are now stored at the Kochi Core Center. Fossil corals will be described at the lowest taxonomic level possible. Variations in taxonomic and morphologic compositions of fossil corals will be interpreted in terms of paleoenvironmental and paleo-water depth changes based on our current knowledge of the distribution of coral species on modern reefs in the same region, derived from the data acquired during this research project and from the scientific literature. In addition, samples of coralline algal crusts will be taken to complement the analysis of coral assemblages and their paleoenvironmental interpretation. Due to their wide latitudinal separations, analysis of coralgal assemblages in these cores is expected to shed light on the responses of reef-building communities to sea-level and environmental changes near the limit of their latitudinal range of distribution.
Depending on the timing of the core study mentioned above, the next ROV-AUV survey around the Sekisei Lagoon is expected be schedule toward the end of FY2019 or during FY2020.
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| 次年度使用額が生じた理由 |
The budget for FY2019 will be used to conduct core description and sampling at the Kochi Core Center. In addition, another ROV-AUV survey around the Sekisei Lagoon is expected to take place during FY2019, or will be scheduled at latest during the first half of FY2020.
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