Shelf Sea Biogeochemistry sediment water nutrient flux incubations.

This data set contains nutrient flux measurements from sediment cores collected from the Celtic Sea across the four Natural Environment Research Council (NERC) Shelf Sea Biogeochemistry (SSB) surveys (DY008, DY021, DY030, DY034) on-board the RRS Discovery (2014-2015). The data set includes both raw time course values and overall summaries. The author does not have any concerns over the quality of the data set and values are consistent with similar data reported in the wider literature. All sediment was collected using the NIOZ box corer and sub-cores collected for incubation in temperature controlled tanks. Water samples were then extracted at intervals, refrigerated and analysed on-board for nutrients. Five vertical sediment cores were collected in 40 cm long x 10 cm i.d. clear plastic tubes, at each site one from each of five different NIOZ cores. The overlying water in each core tube was topped up to approximately 1000 ml with site water. The cores were immediately placed in a thermostatically controlled water bath at the temperature of the overlying water at that site. The water overlying each core was gently aerated and stirred to prevent oxygen depletion. Three similar core tubes were incubated with approximately 1000 ml of site water as a control. After an equilibration period, sub-samples of the overlying water were removed by syringe at roughly hourly intervals for the first one to six hours then further samples were taken at approximately twelve to eighteen and 24 to 36 hours after t = 0 to complete the time-series. All these sub-samples were immediately filtered through a 0.2um syringe filter and placed in an air-tight vial for later analysis. Once analysed, the nutrient concentrations were corrected for the volume of overlying water (which was routinely measured) and the results plotted against time. The flux between the overlying water and sediment of each core was calculated from the slope of the linear portion of the graph (P<0.1) and converted to a flux in umol. m^-2 d^-1. The mean and standard deviation of the fluxes from the five cores was then calculated. The error on the nutrient flux associated with each individual core was defined by the standard deviation of the linear regression analysis used to define the linear portion of the graph. The rate change in the control cores are calculated by the same method. The results from the controls may be subtracted from the sediment fluxes to obtain the contribution of sediments alone to the total nutrient transformation. The inorganic nutrient samples were analysed using a 5 channel (nitrate, nitrite, phosphate, silicate and ammonium) Bran and Luebbe AAIII segmented flow, colorimetric, autoanalyser. The analytical chemical methodologies used were per Brewer and Riley (1965) for nitrate, Grasshoff (1976) for nitrite, Kirkwood (1989) for phosphate and silicate, and Mantoura and Woodward (1983) for ammonium. The data were collected as part of the SSB research programme as part of the Biogeochemistry, Macronutrient and Carbon Cycling in the benthic layer (BMCC) research programme. SSB was co-funded by NERC and the Department for Environment, Food and Rural Affairs (Defra). The programme took a holistic approach to the cycling of nutrients and carbon and the controls on primary and secondary production in UK and European shelf seas, to increase understanding of these processes and their role in wider biogeochemical cycles. The British Oceanographic Data Centre (BODC) created the metadata entry and is responsible for holding master copies of the data.