RRS James Cook Gears for Whittard Canyon Survey
On August 9, 2015, RRS James Cook will set sail for a five-week expedition in the NE Atlantic, led by NOC scientist Dr Veerle Huvenne.
This will be the first-ever British expedition to simultaneously use three different types of deep-submergence robotic vehicles.
The Autonomous Underwater Vehicle (AUV) Autosub6000 and the Remotely Operated Vehicle (ROV) ISIS, both from the MARS fleet at the National Oceanography Centre, Southampton, will be joined by an underwater Seaglider from University of East Anglia.
Together the vehicles will be used to characterise the seabed habitats and water column structure of a giant deep-sea canyon.
The main target area is Whittard Canyon, one of the largest submarine canyon systems along the Celtic Margin. It extends from 200m to more than 4000m water depth, in places cutting more than 1000m into the continental margin. Submarine canyons are the main transport pathways between the shelf and the deep sea, and are often considered biodiversity hotspots. The complex environment and associated current patterns create a wide range of different niches, each of which attracts specific species. Producing ‘habitat maps’ of the seafloor environment is key to understanding these species distributions.
The steep walls of submarine canyons present a particular challenge for habitat mappers, but are of particular importance as they often host the richest fauna, including vibrant cold-water coral communities. The near-vertical (and sometimes overhanging) rocky terrain means that traditional ‘over-the-side’ equipment, such as grab samplers, sediment corers and towed video frames lowered from the ship, often struggle to provide reliable data. After an initial test in Whittard Canyon in 2009 using ROV Isis, Autosub6000 has now been adapted to become the first AUV to be able to create acoustic maps of vertical cliffs in the deep ocean. The science team will also use Autosub6000 and Isis to collect samples, video and photographs of the seabed, and make acoustic maps throughout the canyon, so that 3D habitat maps can be produced.
In addition, a Seaglider provided by University of East Anglia will be deployed to measure physical properties of the water column (e.g. temperature, salinity, turbidity), during a 25-day programme of vertical profiling strategically planned at several locations within Whittard Canyon. The results will provide information on water column structure and variability throughout the canyon, and on currents caused by internal waves and tides. It has been shown that these have an important impact on the seabed fauna, supplying food particles and preventing species such as cold-water corals from being draped in sediment.
The easternmost branch of Whittard Canyon is a new Marine Conservation Zone, and is the only deep-water marine protected area in English waters. The expedition is therefore being co-funded by Defra to collect additional data from this site to inform their future management measures, such as potential restrictions on activities that damage the seafloor. The expedition will also feature a return visit to the Haig Fras Special Area of Conservation west of Cornwall, to repeat map an area of seafloor with Autosub6000. This site was first mapped and imaged in 2012 – by repeat mapping the site three years later, potential changes to seafloor habitats and faunal distributions can be assessed. This work is being co-ordinated by Prof Russell Wynn of NOC, and will inform Defra about the potential for marine robotic vehicles to undertake future mapping and monitoring of marine protected areas.
Finally, at the end of the expedition, the team will test another piece of novel technology, a vibrocoring system for ROV Isis. It is currently impossible to obtain good-quality cores of seafloor sediments in some deep-sea environments, due to the sandy nature of the seabed. The new vibrocorer is designed to penetrate these sandy sediments, and having the opportunity to test it in some of the sandy deposits in Whittard Canyon is an exciting prospect as it has potential to increase our understanding of sediment transport processes through the canyon.