By Kelsey Archer Barnhill
After several days of transit we are in our target region! The weather is hot (27ºC at the moment) and we sailed through some tropical rain yesterday. Suddenly the temperature-regulated room for the cold-water corals is becoming a popular place to go to escape the heat! Each team is busy getting to work or making their final preparations.
The CTD rosette was deployed in the early hours of the morning for multiple uses. Our physical oceanographer on board, Angela Mosquera, is now processing the data which looks as expected and will complete analyses once she is back on shore. Susan Evans took water samples from the CTD niskin bottles to filter for eDNA. All DNA extraction, amplification and the rest of the processing will be completed on land back at the National Oceanography Centre. RoCSI (the eDNA sampler) will go on its first mission during the upcoming Autosub6000 operation which will act as a trial run for Susan to get some samples for calibration of the protocol, before getting the scientific samples on the following immersion. The cold-water coral team also took some bottles with water from 2000 meters depth to fill the coral husbandry tank. This seawater is taken from depth so the corals will be in water as close to their natural environment as possible once brought on board. The AUV team also placed their AvTrak acoustic communications beacon on the CTD for a test run and were happy to find it working perfectly.
Yesterday and overnight there were some multibeam bathymetry shifts as we mapped our target region off of Cadamosto Seamount to plan where to deploy the landers and the AUV. Veerle Huvenne is now processing the multibeam data we acquired to inform these decisions. At first glance it seemed like the bathymetry was quite flat but upon further inspection there are some interesting features in the details which appear to be small volcanic features, a large flat plateau (the likely target for the first Autosub6000 mission) and small mounted ridges and depressions. There are also some volcanic cones, including one which is 200 meters tall, and some possible flow structures on the seafloor which could be volcanic or sedimentary in origin. We are quite curious to see which animals are down there!
The ROV team is busy making their last-minute preparations as we hope to make our first ROV dive of Leg 1 tomorrow, weather allowing. The team is keeping an eye out on the waves, wind, and currents as well as seeing how the ship’s dynamic positioning system is operating in today’s conditions. We use dynamic positioning to keep the ship where we want it during ROV operations.
Following a non-routine repair on the Launch and Recovery system (LARS) earlier in the week to adjust the tension on the drive chain, the AUV team ran some test operations today. As this is the first time they are deploying Autosub6000 from the Sarmiento de Gamboa, they did a test launch and recovery of a blue barrel into the ocean. This practice run allowed them to test the LARS, see the ship’s motion during a recovery, and to train the newer team members who have not yet done a launch at sea. It also allowed them the chance to practice communicating with the ship’s crew as the team speaks with the bridge during operations to ensure the ship is an appropriate distance away from the AutoSub6000.
The Landers team have been busy all day as they have their first deployment today with the benthic respirometer. The final preparations include putting the beacon on the lander (this is how the team will locate and recover the resurfaced lander), ensuring the water sample tubing is good to go, and getting the injectors ready. Preparing the injectors is the final step as they will be filled with water and isotopically labelled algae which allows the experiment to run. This is done last as bacteria in the water could consume the algae, which would hinder the experiment. Once the lander is on the sea floor, this algae is injected into the seafloor sediment to start incubation. Every nine hours a water sample is taken following injection. Once the lander is recovered the team will look at the food web in the area through exploring organisms like bacteria meiofauna. To look at biogeochemical responses, nutrient fluxes and respiration are recorded as well.
It is really exciting to start off our scientific operations on board and I am looking forward to seeing the seafloor through AUV, lander, and ROV images!