Development and application of chemical sensors mounting on underwater vehicles to detect hydrothermal plumes

The present paper introduces pH sensor named pH-12, ORP sensor named ORP-12, auto multi-water samplers named MINIMONE and ANEMONE, and their applied examples in real waters. They have been developed for the purpose of attaching AUVs and ROVs by our research team, and they are specialized to detect hydrothermal plume signals. In order to mount on AUVs/ROVs, these sensors and samplers are designed as small and lightly as possible. During the years between 2008 and 2012, we applied these new instruments to ROV expeditions in 6 cruises within the Izu-Ogasawara Back Arc and Okinawa Trough, and found two new hydrothermal vent sites. As a supplementary, the paper shows a new methodology to detect hydrothermal plumes acoustically with using acoustic Doppler current profilers. We tested this method with an AUV within the Izu-Ogasawara Back Arc and Okinawa Trough in the summer of 2014, and obtained ADCP's high echo amplitudes which have corresponds to chemical sensor signals.