From March 18 – May 10, 2023, 6 CSSF team members supported the Korea Institute of Ocean Science and Technology (KIOST), which works in partnership with the International Seabed Authority (ISA). The science team’s focus was to conduct research on the hydrothermal vents of the Central Indian Ridge. There were two main objectives for this expedition: 1) to understand the environmental characteristics of the hydrothermal vents and analyze the structure and function of the surrounding ecosystem, as well as 2) to investigate the characteristics of mineral resources formed by hydrothermal activity. The expedition focused on geology but also included some biology. Tasks that required ROPOS included collection of video footage along with biological and bedrock samples.

Leg 1: The focus of Leg 1 was conducted for environmental research purposes and had the aim to characterize hydrothermal vent communities. We performed 11 dives at active hydrothermal vents in 5 newly discovered areas: ONBADA, ONNARE, ONNURI, CHEOEUM and MIRAE and 1 dive at a previously known site for the science team to compare. We also collected bedrock samples along the slope of the Ocean Core Complex so the scientists could detect changes in the rock along the slope. Our team used ROPOS to collect >500 biological samples (including bacterial mat, corals, urchins, squat lobsters and shrimp) via 30 suction samples and 49 sediment cores, as well as to deploy 7 sediment traps. We also collected 38 basement rock samples from ONNURI and 14 chimney and sulphide samples from vent sites, as well as 26 samples of seawater from vent plumes.

Leg 2: The focus of Leg 2 was on geology, where we worked mostly with volcanologists. We performed 15 dives at 10 hydrothermal vent sites. Overall, we collected imagery for 6 active vents and for image mapping at 2 vents, as well as 62 sulphide samples, 46 basement rock samples, 34 sediment cores, 41 hydrothermal vent plume water samples, and >100 biological samples. We also deployed and recovered 2 ADCP (Acoustic Doppler Current Profiler) bottom moorings and 1 hydrophone at a site named DAUM. Notably, during this leg, we tested the performance of our newly developed Korean Remotely Operated Coring System (KROCS), designed for sampling crust cores.

When the science team is investigating a site for potential minerals, we use multibeam echo sounding in combination with a CTD mounted with a Miniature Autonomous Plume Recorder (MAPR; developed by NOAA). MAPR looks for redox potential, or the ability of chemical species to lose or gain electrons. ROPOS being able to sense redox potential allows us to sniff out active or inactive vent sites in real time and at a finer scale during photogrammetry and sample collection. When at the potential area, we record video along a transect in a pattern to cover an area (called ‘mowing the lawn’), while the scientists look for staining of the seafloor along the transect or for a change in temperature. To collect water samples, we get ROPOS to hold Niskin bottles over a black smoker vent with hydrogen sulphide bubbles.

A highlight for both the science and ROPOS teams was the successful sea trial of our Korean Remotely Operated Coring System (KROCS), which proved that it is a viable technology and will allow us to use it on our Korean crust survey in the Pacific Ocean in August! CSSF’s Will Glatt was also able to experience his deepest dive yet with ROPOS, at 3420 m! The highlight for the science team was the discovery of 2 new hydrothermal vents (MARU and SAERO) and 1 inactive mineral deposit (CHEOEUM2).

One challenge we have successfully adapted to on expeditions with KIOST is the language barrier. If you’re new, sometimes it can be difficult to understand which people play what roles on the R/V Isabu. In this situation, you may be able to take cues from the rest of the team and pinpoint the person they seem to be talking to the most. The chief scientist is who we primarily work with during these missions!