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Continental shelf sediments are globally important for biogeochemical activity. Quantification of shelf-scale stocks and fluxes of carbon and nutrients requires the extrapolation of observations made at limited points in space and time. The procedure for selecting exemplar sites to form the basis of this up-scaling is discussed in relation to a UK-funded research programme investigating biogeochemistry in shelf seas. A three-step selection process is proposed in which (1) a target area representative of UK shelf sediment heterogeneity is selected, (2) the target area is assessed for spatial heterogeneity in sediment and habitat type, bed and water column structure and hydrodynamic forcing, and (3) study sites are selected within this target area encompassing the range of spatial heterogeneity required to address key scientific questions regarding shelf scale biogeochemistry, and minimise confounding variables. This led to the selection of four sites within the Celtic Sea that are significantly different in terms of their sediment, bed structure, and macrofaunal, meiofaunal and microbial community structures and diversity, but have minimal variations in water depth, tidal and wave magnitudes and directions, temperature and salinity. They form the basis of a research cruise programme of observation, sampling and experimentation encompassing the spring bloom cycle. Typical variation in key biogeochemical, sediment, biological and hydrodynamic parameters over a pre to post bloom period are presented, with a discussion of anthropogenic influences in the region. This methodology ensures the best likelihood of site-specific work being useful for up-scaling activities, increasing our understanding of benthic biogeochemistry at the UK-shelf scale.

Early diagenesis (ED), the physical and biogeochemical changes undergone in surficial sediments, plays an important role in the biogeochemical cycles of key elements (carbon, nitrogen and oxygen) in highly productive shelf-seas. Modelling the process uses a relatively simple set of mathematical equations to represent the transport and reaction terms. We have calibrated an existing steady-state ED model, which we have expanded to include more processes and variables (e.g. mineralisation of organic matter using iron oxide and sulphate) to examine the fate of the nutrients through sediment water exchanges. Biogeochemical cycles can be affected by resuspension as a result of release or uptake of nutrients, which can also have a considerable effect on primary productivity. Resuspension is a wide-spread transport process in shallow seas due to winds, tides and biological activity. In contrast to previous diagenetic modelling, we aim to model resuspension and its effect on nutrient cycling. We will also study the resuspension effects on reactions such as the reoxidation or burial of reduced compounds and associated nutrients. We will present results from the modelling experiments, showing the relative role of various oxidising agents (oxygen, nitrate, iron oxide and sulphate) during the degradation of organic matter in the sediments. Observations made in the North Sea provide suitable data to calibrate the model. Current results show that the model is able to give realistic representations of sedimentary nutrient profiles from the North Sea. We aim to present preliminary results showing the effect of resuspension on the transport processes of nutrients across the sediment-water interface, and will discuss the implications that this may have on the calculation of nutrient budgets in continental shelf seas. preliminary results showing the effect of resuspension on the transport processes of nutrients across the sediment-water interface, and will discuss the implications that

Early diagenesis (ED), the physical and biogeochemical changes undergone in surficial sediments, plays an important role in the biogeochemical cycles of key elements (carbon, nitrogen and oxygen) in highly productive shelf-seas. Modelling the process uses a relatively simple set of mathematical equations to represent the transport and reaction terms. We have calibrated an existing steady-state ED model, which we have expanded to include more processes and variables (e.g. mineralisation of organic matter using iron oxide and sulphate) to examine the fate of the nutrients through sediment water exchanges. Biogeochemical cycles can be affected by resuspension as a result of release or uptake of nutrients, which can also have a considerable effect on primary productivity. Resuspension is a wide-spread transport process in shallow seas due to winds, tides and biological activity. In contrast to previous diagenetic modelling, we aim to model resuspension and its effect on nutrient cycling. We will also study the resuspension effects on reactions such as the reoxidation or burial of reduced compounds and associated nutrients.We will present results from the modelling experiments, showing the relative role of various oxidising agents (oxygen, nitrate, iron oxide and sulphate) during the degradation of organic matter in the sediments. Observations made in the North Sea provide suitable data to calibrate the model. Current results show that the model is able to give realistic representations of sedimentary nutrient profiles from the North Sea.We aim to present preliminary results showing the effect of resuspension on the transport processes of nutrients across the sediment-water interface, and will discuss the implications that this may have on the calculation of nutrient budgets in continental shelf seas

This paper describes an integrated study of a typical Mediterranean flood event in the Gulf of Lions. A flood with a 5-year return interval occurred in the Têt River basin and adjacent inner-shelf in the Gulf of Lions, northwest Mediterranean, during April 2004. Data were collected during this flood as part of event-response investigations of the EU-funded Eurostrataform (European Margin Strata Formation) project. Southeasterly storm winds led to a flood which directly modified the inner-shelf hydrodynamics. Sediment delivery to the coastal zone during this flood represented more than half of the mean annual discharge of the Têt River to the Gulf of Lions. This river transported a large amount of sand in suspension, representing 25% of the total suspended load, and as bedload representing 8% of the total load, during this event. Sand introduced in the nearshore was transported northwards during the peak storm and nourished a small delta. Fine sediments were separated from coarse sediments at the river mouth, and were advected southwards and seawards by the counter-clockwise general circulation. Fine-grained sediments were transported via a hypopycnal plume along the coast towards the southern tip of the Gulf of Lions and the Cap Creus canyon. The along-shore currents, which intensified from north to south of the Gulf of Lions, particularly between the Cap Creus promontory and the Cap Creus canyon, favoured the transfer of fine-grained sediments from the continental shelf of the Gulf of Lions towards the continental slope. Our results show that floods with a few-year return interval in small coastal rivers can play a significant role in the transport of sediments on microtidal continental margins and their export from the shelf through canyons. © 2008