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A carbon budget for the northwest European continental shelf seas (NWES) was synthesized using available estimates for coastal, pelagic and benthic carbon stocks and flows. Key uncertainties were identified and the effect of future impacts on the carbon budget were assessed. The water of the shelf seas contains between 210 and 230 Tmol of carbon and absorbs between 1.3 and 3.3 Tmol from the atmosphere annually. Off-shelf transport and burial in the sediments account for 60–100 and 0–40% of carbon outputs from the NWES, respectively. Both of these fluxes remain poorly constrained by observations and resolving their magnitudes and relative importance is a key research priority. Pelagic and benthic carbon stocks are dominated by inorganic carbon. Shelf sediments contain the largest stock of carbon, with between 520 and 1600 Tmol stored in the top 0.1 m of the sea bed. Coastal habitats such as salt marshes and mud flats contain large amounts of carbon per unit area but their total carbon stocks are small compared to pelagic and benthic stocks due to their smaller spatial extent. The large pelagic stock of carbon will continue to increase due to the rising concentration of atmospheric CO2, with associated pH decrease. Pelagic carbon stocks and flows are also likely to be significantly affected by increasing acidity and temperature, and circulation changes but the net impact is uncertain. Benthic carbon stocks will be affected by increasing temperature and acidity, and decreasing oxygen concentrations, although the net impact of these interrelated changes on carbon stocks is uncertain and a major knowledge gap. The impact of bottom trawling on benthic carbon stocks is unique amongst the impacts we consider in that it is widespread and also directly manageable, although its net effect on the carbon budget is uncertain. Coastal habitats are vulnerable to sea level rise and are strongly impacted by management decisions. Local, national and regional actions have the potential

The Time Averaged Gradient (TAG) approach was applied to measure long-term dry net exchange fluxes of NH3 and SO2 to three contrasting temperate grasslands in the UK. The measurements were made at: Auchencorth Moss, an acid peatland site with little grazing; Plynlimon, an upland grassland on mixed soil and significant sheep grazing; Easter Bush, an intensively managed permanent grassland with N fertilisation, used for silage and cattle and sheep grazing. A data series of five years, from 1999 to 2003, for SO2 and a data series of two years, from 2001 to 2003 for NH3 was obtained at Auchencorth Moss. The measurements provided a characterisation of the chemical climate, meteorology, turbulent characteristics, as well as deposition-emission fluxes at the field site. At Plynlimon, fluxes of SO2 and NH3 were measured from June 2000 to September 2003. A refined TAG system was implemented to improve estimates of gradients and reduce uncertainty on the fluxes, and was applied at Easter Bush measuring NH3 fluxes from autumn 2001 to spring 2003, and at Auchencorth Moss from autumn 2004 to date. The TAG systems provided long-term series of average net fluxes of SO2 at -7.04 ng m-2 s-1 and -3.4 ng m-2 s-1 at Plynlimon and Auchencorth Moss, respectively. The data do not permit accurate description of short term fluxes, but provide long term estimates of S dry deposition for comparison between sites. For ammonia the dry deposition fluxes were on average -7.6, -5.98, and -12.2 ng m-2 s-1 for Auchencorth Moss, Plynlimon and Easter Bush respectively, indicating differences in NH3 concentrations and exchange processes. Several discrepancies in NH3 flux between sites reflect the interaction of temperature, rain and different grassland managing regimes.

The geographical patterns in rainfall acidity in Scotland show a pronounced gradient from the least polluted areas of the north-west at 5–15 μeq H+l−1 to the south-east where annual rainfall-weighted mean acidity is 45–55 μeq H+l−1. The pattern in mean acidity and wet deposition results partly from depletion of the pollutants with distance from the major source areas of Europe, but also from meteorological and orographic effects. Analysis of rainfall data shows that about half of the north-west-south-east gradient in mean acidity results from orographic effects. These enhance the impacts of relatively unpolluted rain in the west and shelter east coast regions from the same, while relatively polluted rain from easterly trajectories is enhanced on high ground in the east and west coast districts are sheltered. The simple analysis provided quantifies the importance of orographic effects on wet deposition in Scotland and implies that for satisfactory estimates of regional wet deposition from long-range transport models, orographic effects must be incorporated.

The relationship between exportable or 'new' primary production to the actual exported primary production in shelf seas is key to understanding the role of phytoplankton production in the delivery of carbon to the seabed. We measured new and regenerated primary production in surface waters at a coastal Antarctic site and related it to direct measurements of particle flux using sediment traps. The study site is the location of a long-term study, the Rothera Oceanographic and Biological Time Series. Upper water column new primary production from rate measurements were shown to be in agreement with estimates calculated from concurrent nutrient deficit measurements, providing confidence in our new primary production estimates for this region. Comparison with sediment trap flux measurements showed that at this coastal time series site (total water column depth 520m) ~2% of the upper mixed layer new production was exported to traps at 200m and 400m depth. The maximum particle flux rate to sediment traps at a site further offshore (total water column depth 820m) was lower than the flux at the coastal time series site but flux of particulate organic carbon was at similar rates during the high flux period. Remineralisation in the upper water column occurred above the upper sediment traps at both sites, with minimal remineralisation below 200m. Overall this study shows this highly productive region on the Western Antarctic Peninsula is best characterised as 'high recycling and low export'.