Preliminary report of marine macrofauna of Nishinoshima Island

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  • 西之島の海洋生物相の速報

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Abstract

The environment and marine macrofauna around Nishinoshima Island were investigated in July 2021. Muddy seawater was observed west of the island, probably due to the volcanic eruption. The seabed off the island's north was covered by volcanic ash and lava over 3 m, and pointed rocks that looked like volcanic bombs dotted the area. During this survey, over 253 species in 14 phyla were observed, mainly on the northern beach and in the northern sea. The biodiversity of benthic animals was low; therefore, macroalgae and corals were not observed. Hydrozoa and Bryozoa were abundant on the seabed rocks. Since they advance on the bare seabed when the marine benthic ecosystem recovers, this indicates that the benthic fauna around Nishinosima is in the early conveyed status of recovery. The plankton biomass was very low due to the poor nutrient content, and larvae of benthic animals were only 1.5 % of all plankton. From the above, it will take time for new benthic animals to occupy the area and gain a foothold in the marine ecosystem around Nishinoshima. It is possible that the benthic fauna will remain in the deep sea near the island after the eruption in July 2020. If benthic animal larvae move in from the deep sea, the primary succession will advance faster. In this study, the primary succession status of the marine ecosystem around Nishinoshima was confirmed. Future studies should monitor the primary succession around oceanic island Nishinoshima regularly, concerning the deep sea, the current around it, and the breeding season of each species.

Journal

  • Ogasawara research

    Ogasawara research 49 113-168, 2023-03

    東京都立大学小笠原研究委員会

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