Tow-yo transects in Loihi Seamount by Brian

The critical time had come. We and the R/V Thompson were right above Loihi Seamount, which is located south of the Big Island, Hawaii. Loihi Seamount is known to be ‘an island in the womb’ because it has been showing volcanic activities that indicate that this seamount will be the next Hawaiian Island created by the hotspot.

A couple of us (Ben, Erik, Sam) including myself had planned to get water samples from the buoyant plume that is dispersed from a deep sea volcanic vent system called hydrothermal vents. We knew approximately where to look for the buoyant plume by reading multiple previous researches but we were unsure if we would actually be able to find the plume. Without getting the water samples directly from the hydrothermal plume, our projects were meaningless. The way to find the plume is to use an instrument called a CTD that has various sensors that are very useful for oceanography research and do tow-yo transects which is pretty much doing yo-yo with the CTD cast in certain depth ranges (in this case 1200m~1260m) to find the signals of the plume and collect water samples by closing bottles attached to the CTD cast. We were planning to do a total of four tow-yo transects which would take about 12hours. As we were preparing for the first transect, we were getting quite nervous; we were totally unsure how many water samples we would be able to get.

On the first transect, things were not going very smooth. Precise tow-yo transects needed lots of consideration because we didn’t want to get too close to the bottom of ocean and cause trouble. Marine technicians ended up pulling the CTD cast back to surface and attached an echo sound dispersing system that would help detecting the bottom of ocean. After that everything went well. As we were all gathered in computer room and monitoring the process, we saw multiple signals (increasing temperature and decreasing light transmissivity) of the plume in each runs and we fired bottles to collect the water samples. Intense tension that we had was relieved as we were collecting more and more samples. Finally, after finishing the last transect, we ended up collecting a satisfying amount of good looking samples. All we have left to do now is to bring the water samples back to Seattle and analyze them in laboratories. So far our cruise has been fantastic and successful.