Figure 1

Map showing sampling sites off of Japan. OT = Okinawa Trough, YZ = Suruga Bay, and HD = offshore Hokkaido. This map was made with Natural Earth (free vector and raster map data, https://www.naturalearthdata.com, 1:10 m Cross-blended Hypsometric Tints, version 2.0.0) using the free and open source QGIS version 3.18.1 (https://qgis.org/en/site/).