RRS Discovery Cruise DY034, 06 Aug - 02 Sep 2015, Southampton to Southampton. Shelf sea biogeochemistry

We addressed four interdisciplinary themes to provide a holistic view of the biogeochemistry of benthic shelf ecosystems, including the nepheloid layer. The relative size of the carbon (C) and nitrogen (N) pools, microbial transformation rates and fluxes between pools were quantified in shelf sediments on this, the last of several integrated cruises (Winter, post-bloom Spring, late Summer) scheduled to coincide with contrasting biogeochemical conditions. During each cruise, observations and experiments are to be made across a gradient of soft cohesive mud to coarse advective gravel. The effort has four modules: Module 1: Biogeochemical cycling of nitrogen, phosphorus, silicon and carbon within sediment; Module 2: Role of sediments in carbon storage; Module 3: Role of macrofauna and the impacts of natural and anthropogenic disturbance on sediment biogeochemical processes; Module 4: Role of sediment resuspension and near-bed current flow: Impacts on carbon and nutrient sediment-water exchange in diffusive and pumped sediments. Four primary sites were selected based on representation of the dominant habitat types (% area covered/ biogeochemically activity) within the Celtic Sea. This approach is to ensure that all data generated are applicable to the largest area of shelf sediments and thus suitable for scaling-up activities. Sites were chosen from a limited depth and temperature range to ensure high comparability between sites. Notably this was the last scientific research cruise of the Shelf Sea Biogeochemistry programme.