…deep ROV dives, coral chalêts, sharks and strange visitors
Blog entry by Luis Greiffenhagen, NOC
It has been very busy on the RRS James Cook since we arrived at Whittard Canyon. Our shifts have started, we all got used to our routine and responsibilities. Especially in the first days, there are always a few technical issues and plans change very quickly. But most importantly, we already had some successful missions and collected lots of data – here is an update on what happened so far since Monday:
After we took our first deep CTD (conductivity, temperature, depth) sample (4007m), in the morning hours of Monday we reached the easternmost part of Whittard Canyon, which is still in British waters, e. g. The Canyons Marine Protected Area (MPA). This area includes two stunning canyons, the Dangeard Canyon and Explorer Canyon (>1000m depth), separated by two large interfluves (300-400m depth).
On one of these interfluves, small, extinct coral mounds (click here if you want to know more about mounds) and trawl marks from fisheries were previously found. In order to further explore this area, the brand new AUV Autosub 5 and our ROV Isis were sent on their first missions. Through re-mapping the area at high resolution, taking photo-/video transects, sediment cores, water samples and sub-bottom profiles we want to see how the area changes over time.
Excitement levels were super high when our ROV Isis went into the water for the first time. Due to the pandemic, it has been more than three years since Isis did her last dive. Therefore, we all took some time to get used to the procedures in the ROV container again, which is full of screens, displays and controllers. While the pilots sit in front, there are two or three scientists sitting at the back, directing the different operations, the science camera and logging observations. Once we arrived at the bottom – which every time feels a bit like landing on the moon – there were huge schools of Boarfish (Capros aper).
As part of the ROV Dive, we deployed very exiting experiments by James Strong (NOC) and Louise Allcock (National University of Ireland, Galway) on the ocean floor. “ARMS” (Autonomous Reef Monitoring Structures) is a structure that provides surface for coral (and other invertebrate) larvae to settle. Due to coral reef degradation worldwide, these structures have been widely and successfully used in tropical coral reefs for coral restoration. Deep-sea coral reef restoration is just in its infancy, and in order to find out which substrate is best for larvae settlement, James additionally mounted roof tiles, partly covered in lime on top of a square framework. The plan is to come back in a few years to that location and see if it has been colonised by cold-water coral species. Due to its familiar looks, the structure has earned a few nicknames on the ship, such as “coral chalêt”, or, less glamorous, “settlement shed”…
The second ROV dive followed after a short transit to Explorer Canyon, where we went back to look at a massive wall. After a few hours we crossed the canyon, went through the thalweg at around 950 meters depth to then re-visit the known cold-water coral reef of the Explorer canyon. It was incredible to see such a biodiverse, colourful animal garden created by the habitat-forming species Desmophyllum pertusum (former Lophelia), Madrepora oculata, but also lots of crabs, anemones, the endangered fish orange roughy (which can live over 200 years) and other rather weird creatures. We repeated a high-resolution 3D model of the reef in order to see how the reef changed in comparison to the last cruise. It looked healthy, however, we saw quite a lot of litter, which can be worrying considering that we are hundreds of miles offshore. Further, we took some biological and geological samples in the area to better understand seabed processes, organic carbon and microplastic contents (more on that soon!).
Last but not least, we mapped the last blank spot on the map of our British conservation zone (MPA) with our shipboard multibeam echo-sounder.
In our breaks, we were able to see some amazing marine life from the deck: Lots of dolphins accompanied us on the way to Whittard Canyon, and there have been sightings of some whales in the distance. While we could not capture those on photo, we had an epic encounter of our ROV with a Porbeagle Shark (Lamna nasus) at around 70 meters depth (see video clip below – © ROV Scorpio Camera, NOC). The very fast and agile species is from the same order of sharks as the famous great white and came to say hi to us.
Besides that, we realised that we have some unusual passengers: There is a non-flying pigeon onboard – It must have boarded the RRS James Cook (without security check!) just before leaving Southampton and has ever since been observing our on-deck operations with curiosity. We are currently in the process of finding a good name, so do not hesitate to contact us about this.
We will update you soon on our next missions!