Recent Deep-Sea Benthic Foraminifera from an Active Volcanic Area: First Insights around Nishinoshima, Northwest Pacific

This study reports the preliminary results of the first analysis of benthic foraminifera of seafloor surface sediments from the Nishinoshima volcanic area. The samples were collected in 2015 during several DEEP TOW (deep ocean floor towed survey system) dredges on the summit and flank of Nishinoshima-Minami Knoll, a knoll ∼8 km southeast of Nishinoshima Island that forms part of the same submarine volcanic edifice. The two stations DT-1170 (N9) and DT-1173 (N12) were sampled from water depths of 1062–1015 m and 516–203 m, respectively, and were located at distances of 10 and 8 km from the main Nishinoshima edifice, respectively. The two stations displayed a typical faunal structure for deep-sea environments, with low foraminiferal densities but highly diversified assemblages. A total of 131 species, excluding undetermined porcelaneous and hyaline species groups, were found, and are recent deep-sea benthic foraminifera previously identified in the bathyal depths around Izu-Bonin volcanic arc, or species found in the Neogene land-based strata in the western Pacific region. We conclude that the bathyal benthic foraminiferal assemblages in the studied area are likely to be free from recent volcanic activity. We provide detailed taxonomic descriptions of the 21 commonly occurring species. This exploratory study therefore provides crucial basic information about benthic foraminiferal faunas in the Nishinoshima area, which could be used in future environmental analysis of this highly dynamic region.