JC036 (19/06/2009 - 28/07/2009)
Background - Taken from JC036 cruise Report
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 HERMES and HERMIONE Projects, led from NOC, 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-coordinated, 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 cruise JC36 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 programme 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.
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