Utilization of acoustic video camera for investigating mid oceanic ridge

We wanted to have some observational method to evaluate hydrothermal discharging behavior as it was. DIDSON is an acoustic lens-based sonar. Institute of Industrial Science, University of Tokyo (IIS) has understood DIDSON's superior performance and tried to find new method for utilization of it. A next challenge is to develop an observation method based on DIDSON for hydrothermal discharging from seafloor vent. In October 2009, we conducted seafloor reconnaissance using a manned deep-sea submersible (DSV) Shinkai 6500 in Central Indian Ridge 18-20deg. S, where hydrothermal plume signatures were previously perceived. DIDSON was equipped on the top of Shinkai 6500 in this cruise. DIDSON could obtain acoustic images of seafloor hydrothermal flows, even though we could not fully utilize the performance of DIDSON due to low-quality wire connection between DIDSON and Shinkai6500. Contrasting density inside the acoustic image of the hydrothermal flow could be distinguished. DIDSON showed its possibility of observation tool that can delineate spatial and temporal change of internal structure of the hydrothermal flows.