Marine robots helped capture the first truly three-dimensional pictures of submarine canyon habitats. The new maps include a 200 km canyon but also include details as fine as individual cold-water coral polyps. They will be used to help manage only English Marine Conservation Zone in deep water.
The map was created during a recent scientific expedition to the Whittard Canyon in the Bay of Biscay, and was led by the National Oceanography Centre (NOC). The maps are nested, much like a set of Russian dolls, with the most detailed map sitting within a larger scale one, which sits within a larger map still.
Submarine canyons are some of the most complex deep-sea environments on this planet, and are known to be potential biodiversity hotspots. Similar to canyons on land, submarine canyons can have steep flanks, with vertical cliffs and overhanging rock formations. Until recently these parts were out of reach for traditional types of marine equipment, which made them the ‘forgotten habitats’ of the deep sea. By using unique robot technology to collect data in these ‘hard-to-reach’ areas, the results of this expedition will lead to a better understanding of the biodiversity patterns in the canyon and of the processes that drive them.
Echo-sounders on the RRS James Cook were used to create a 200km map of the canyon with a 50m pixel resolution. Using a newly-developed sideways-directed echo-sounder, the Autosub6000 robot-sub, maintained by the NOC, was able to map vertical walls within the canyon with a resolution of 3-5m per pixel. At the same time Isis, the NOC-maintained Remotely Operated Vehicle, was lowered from the RRS James Cook on a tether to record high definition video and to collect biological and geological samples from vertical and overhanging locations. Echo-sound data collected with Isis was also used to create the most detailed map of the three, with a resolution of 10-20cm.
“Our robot vehicles imaged rich communities of cold-water corals, clams, deep-sea oysters and their associated fauna, including a broad range of fish species,” said Veerle Huvenne of the NOC, who led the five-week expedition. “We also captured amazing footage of Blue Sharks and Swordfish when the Isis marine robot was traveling to and from the seabed.
The morphology of this canyon is spectacular. We have mapped cliffs up to 150m high and 1.6km long, in some locations down to centimetre-scale resolution. This makes us the only group in the world who currently can image vertical cliffs in the deep sea in this way. ”
The Whittard Canyon proved to be a highly dynamic environment, with strong internal tidal flows and containing deep plumes of organic-rich sediment. To study these oceanographic processes, the University of East Anglia’s robot glider was used to continuously measure the water column. “Our Seaglider collected a fantastic dataset and revealed the presence of internal waves up to 80 m high; these processes are likely to have a major influence on the distribution of habitats and fauna within the canyon,” said Tahmeena Aslam, who was responsible for the glider from UEA.