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Submarine canyons provide one of the main conduits through which sediment passes from the continental shelf, across the continental margin, and into the deep ocean. They redistribute pollutants from the land and shelf seas to the deep ocean, may play an important role in carbon storage, and have a powerful influence on the structure and biodiversity of benthic ecosystems and the biogeography of species.

When sealevel rose at the end of the last glaciation, many canyons lost their connection to sediment sources that were active at low sealevel. As a consequence, some canyons on the European margin, such as Setubal Canyon on the Portuguese margin, became largely inactive; others, such as Nazare Canyon, have been transformed into sediment traps that are presently accumulating large volumes of sediment, whilst a third group, such as Whittard Canyon in the Bay of Biscay, are thought to remain active as sediment transport conduits. The variable nature of present day canyons is only just becoming apparent and remains little understood. What processes bring sediment into the canyon? What drives episodic sediment transport processes (e.g. turbidity currents) and how often do they occur? How do canyons interact with ocean currents? What influences, beneficial or otherwise, do sediment transport processes exert on canyon benthic ecosystems?

The EU-funded HERMES and HERMIONE projects, led from NOCS, have developed a comprehensive strategy for the study of Europe’s continental margin. Particular attention is being given to canyons as important ‘hotspots’ of biodiversity and biomass. Canyons are complex systems, highly variable in terms of their hydrography, sedimentology, biogeochemistry and biology, and each with its own characteristics. To create useful policies for whole ecosystem management there is a clear need not only for a concerted effort to compare canyons from different biogeochemical provinces and different topographic settings, but also for co-ordinated, multidisciplinary projects relating the fauna to the environmental variables that regulate their distributions. These objectives are shared by the NERC funded OCEANS 2025 programme.

To address these objectives we will undertake sediment coring, current measurements, water column measurements, video observations, biological sampling and in situ biological experiments in canyons on the northern Bay of Biscay margin.  Recent and long-term (glacial-interglacial) sedimentation rates and processes will be determined, as will the driving mechanisms of present-day processes.  The proposed cruise will build on work completed on several previous cruises, including CD157, CD179, D297 and JC10 to the Portuguese margins. The JC10 ROV cruise demonstrated the extreme heterogeneity of the canyon environments (on metre to tens of metres scales) and provided a compelling justification for the use of the ISIS ROV in canyon investigations.

 

JC36 programme

The seagoing programme on JC36 will focus on the Whittard Canyon on the northern slope of the Bay of Biscay.  The Whittard Canyon region is much less well studied than the canyons on the Portuguese margin on which we have previously focussed, although regional swath bathymetry data are available and three reconnaissance ROV dives were undertaken during JC10 in 2007.  These dives provided evidence for high-energy sediment transport processes in the canyon axis and for the occurrence of rich and diverse biological communities, including cold-water corals, on the canyon walls.  Because of the lack of pre-existing data, particularly high-resolution survey data and sediment cores, from Whittard Canyon, cruise JC35 was designed to collect high-resolution survey data for the entire canyon system, principally using the TOBI 30 kHz sidescan sonar system. Right: Location map showing the position of the Whittard Canyon

On cruise JC36, we will begin the programme of biological and geological research by carrying out a series of ROV video transects (using the remotely operated vehicle Isis) to determine variations in species and community structure and composition in different geological and topographic settings down the canyon. Once suitable sites have been located on the ROV transects, we will, in particular: (i) undertake detailed studies of recognised biological hotspots on both hard and soft substrates (ii) collect specimens for taxonomic studies, including molecular genetics (iii) carry out biological experiments including the use of in situ incubation chambers and tracer feeding experiments to study the physiology of deep-water fauna (iv) install a lander with an upward-looking ADCP to measure currents within the canyon axis.  A small unit, deployed by ROV, but heavily-weighted to ensure survival if turbidity currents occur during the deployment, will be used. (v) collect a suite of piston cores to examine the recent sedimentation history of the canyon and, in particular, to investigate whether sediment is currently accumulating in any part of the canyon. Left: Plan of ROV investigations in the Whittard Canyon

Follow the progress of the cruise via the cruise blogs or send the team a question using our Q&A page.