By Kelsey Archer Barnhill
A few months ago I helped the UK Primary Science Teaching Trust put together a slideshow about being a deep-sea ecologist for their teaching resource initiative ‘A Scientist Just Like Me.’ The goal of these slideshows, aimed at young children, is to encourage schoolchildren to consider what scientists are like and what types of skills are required. I was asked to provide four skills that are needed which children could relate to. The very first one I chose was creativity, which I explained with “getting a robot to the seafloor to retrieve an unusual animal certainly takes a lot of imagination and problem solving!“
Well, creativity, imagination, and problem solving were all certainly used on board the Sarmiento de Gamboa over the past few days! Technical difficulties with the Autosub6000 have meant that Susan Evans and Erik Simon Lledó have been hard at work with the technical teams to adapt current on board technologies to collect their data.
While Susan has successfully collected eDNA samples with RoCSI on Autosub missions, she would like to ground-truth the method by correlating organism presence in her eDNA samples to organisms seen in ROV images at the same site. Erik, whose work is focused on abyssal biology, has not yet obtained any seafloor image data on this cruise which is needed for his research. In order to conduct their research, Susan and Erik have been hard at work collaborating with all teams on board – along with some friends on land – to come together and solve the problem.
Today ROV Luso was refitted to prepare for its deepest dive ever, into the abyss for this mission. On our most recent dives, Luso has been operating without one of its thrusters. As there are multiple thrusters, this is a risk the team are willing to take when diving within their normal range. However, the upcoming mission is planned to dive to around 3400 m, pushing Luso 150 m deeper than its current record. Luso is rated to dive to this depth but has not needed to until now. For the team to feel confident about sending the ROV down so deep, they needed to get another thruster for more operational control and to make the ROV quicker. However, there was not a spare one on board. Though we are operating close to Cabo Verde and can often see an island or two on the horizon during the day, we are not allowed into port because of COVID-19 restrictions. Luckily we have a friend and colleague from Leg 0, Herculano Dinis, Executive Director of the Projecto Vitó Association, who lives on Fogo. Herculano was able to get the part we needed, and bring the propeller to the ship via a boat transfer which involved the Cabo Verde Policia Maritima. We crowded out on deck as we watched his small boat approach us, and the ship’s crane lowered down a bag to collect the part once the two ships were side by side. After a successful transfer, spirits on board both ships were high as we waved our goodbyes and thanked the team with a few blasts of the ship’s horn, which was answered by the Policia’s siren.
Our heroes! Video © Antonio Calado / EMEPC / iMirabilis2
With Luso now fully functional to dive to 3400 m, the next step was to offload RoCSI from the Autosub6000 and load it onto the ROV. The ROV team, AUV team, and Susan all worked together to first install RoCSI onto Luso’s frame and then secure it, protecting the syringes from movement and vibration with a plastic shield. RoCSI is now situated behind the ROV sampling drawer, and fits nicely into the frame without anything needing to be removed.
The final steps, which are ongoing, are to attach cameras for Erik’s work onto Luso. A new structure was built on the front of the ROV, where the ROV stills camera and the benthic lander team’s camera will both be mounted on a pole, along with lights for taking the pictures. The camera borrowed from the lander team will be the primary camera used for data collection and the ROV stills camera will be used for backup, as it has lower resolution.
The cameras will both point straight down at the seafloor, as opposed to the standard ROV cameras which are angled slightly forward for navigation and sampling purposes. For Erik’s work, the cameras must be mounted perpendicular for an overhead image of the seafloor. The ROV will also move differently than normal as it is important to fly at a constant speed and maintain a constant altitude on this mission. Constant speed is important as images are taken at a fixed interval, and moving at a known and fixed rate ensures the seafloor images don’t overlap. A constant altitude is needed so we can measure the size of organisms – this can be calculated from the pixel size of the image. The normal 4K video will also be recorded during the dive but this is secondary and will be used for qualitative purposes only; Erik’s survey is based on obtaining fully quantitative data.
The ROV will fly over an exact amount of area and so that we can quantify animal sizes to compare to previous work. These types of surveys are standardised so work done across regions and teams can be compared. Erik hopes to survey two locations: one north and one southeast of Cadamosto seamount. It is possible that one site is more exposed than the other – this hasn’t been confirmed due to lack of hydrological data, but there are higher shallow currents present at the north site. If there is a difference in environmental parameters, this could impact abyssal communities. Erik’s image work will be combined with results from Susan’s RoCSI samples to see if the two survey methods of quantifying biodiversity correlate.
The ROV pilots have been in discussion about how to adapt to this new survey method. The current plan is to try a combination of manual piloting and the auto-altitude setting. When the area is flat, the auto-altitude setting can be used but manual piloting will be needed for any larger or sudden elevation changes. They will be following a zig zag pattern in the survey Erik has prepared, with each line 600m long. To keep their speed constant they will need to maintain focus as currents can impact speed, meaning they will need to adjust trim accordingly. This dive will be technical and new for the ROV team, but they are up for the challenge!
It is truly impressive to see the creativity, problem solving, and most importantly, teamwork which have all worked together to make this new plan a reality. Let’s hope the weather is on our side to get Susan and Erik their data and Luso a new depth record!