By Kelsey Archer Barnhill
After a stormy day yesterday with rain, thunder and lightning, this morning we woke up to bright blue skies and a lovely view of Brava Island. The tropical blue sea is calm as the ship stays still to complete some sampling. Earlier today we sent down the box corer to see if there was sediment on the seafloor. Once we confirmed the ship was stationed over a target area with sediment, the multicorer was sent down to take the sediment samples. When the multicorer returns to deck, the top 1 cm of each multicore sample will be preserved for foraminifera analyses. This work, led by David Thornalley at University College London and Irene Perez at Instituto Español de Oceanografia, will use benthic foraminifera distribution across a depth gradient to explore decadal-millennial changes in ocean ecosystems.
Images from the baited camera trap which was retrieved a few days ago, were shared around the ship today and we got to view the incredible pictures of cusp eels, rat fish and other scavenger fish who were attracted to the mackerel. Yesterday the trap was re-deployed with squid as bait to compare the types of scavengers attracted to each bait type. As climate change is predicted to favour squid under future environmental conditions, these studies help explore how ecosystem functioning may change if squid become the main food source for scavenging organisms. One interesting find from the first deployment was the lack of amphipods, which are often common during these deployments, but in this case only a few were seen.
Above and below: Images from the baited camera lander. All images © Andrew Sweetman / Lyell Centre-Heriot Watt University / iMirabilis2
Last night the resiprometer was recovered and successfully brought back on board (see video, left, courtesy of Veerle Huvenne). The samples obtained from the deployment were preserved in formalin. This afternoon, Daniëlle De Jonge and Alycia Smith sieved through the sediment collected to look for foraminifera. After hard work sieving in the hot hanger, their hard efforts were rewarded as plenty of foraminiefera were visible under the microscope. Prof. Andrew Sweetman spent the morning doing winkler titrations to measure the respiration in the samples collected from the lander. From the processing he found the area we are in is very productive. The third lander, the baited trap, is loaded with mackerel and is still on the seafloor, which we will recover tomorrow along with the baited camera lander. Once this lander is recovered we will have our first deep sea fish samples on board.
The AUV team is hard at work ensuring the Launch and Recovery System (LARS) is fully operable for the next dive. On the upcoming mission, the AUV will be sent to collect high resolution multibeam data. Once the target area is surveyed and its mild topography confirmed, the AUV can be sent on a photographic mission. Photos are taken 3 meters off of the seafloor so there cannot be any sudden changes in topography that could trigger the Autosub6000’s auto collision sensor to trigger. Once the mapping and subsequent photographic mission are complete, the scientific AUV team on board can start processing the photographs.
The ROV team is hard at work preparing for our next dive. Luckily they had some time to share the images from the first dive with me. So please enjoy some image highlights from the island of Fogo’s continental shelf! All images below © ROV Luso / iMirabilis2