DOI: 10.5285/47634703-04c9-31e5-e053-6c86abc046e3
title: Quantification of macrofaunal activity under climate change scenarios from RRS Discovery cruise DY008.

description: This data set contains incubations with sediment cores to assess climate change on macrofaunal activity in the Celtic Sea. The data were collected between 1<sup>st</sup> April 2014 - 31<sup>st</sup> October 2014 on board the RRS Discovery cruise DY008 and subsequent mesocosm incubation at the Biodiversity Ecosystem Futures Facility (BEFF) at the National Oceanography Centre, Southampton (University of Southampton). The authors do not have any concerns over the quality of the data set and values are consistent with similar data reported in the wider literature. Replicate sediment cores (n = 10) of size 20 cm by 20 cm and depth 12 cm were collected from NIOZ cores taken at 4 sites (Muddy, site A; Sandy Mud, site G; Muddy Sand, site H; and Sand, site I) in the Celtic Sea.  These sediment cores were transferred to clear perspex mesocosms and at the end of the cruise, all aquaria were transferred to and maintained in the BEFF for a 6 month incubation. Five cores from each site were allocated to one of two scenarios: ambient or future conditions. In the BEFF aquaria were held in large water bath tanks in the dark, representative of bottom conditions in the Celtic Sea, and continually aerated by bubbling either ambient air or a treatment specific air-CO<sub>2</sub> gas mixture through a glass pipette. Aquaria receiving ambient environmental conditions were held at 10.92 +/- 0.40 degrees C (approximating the mean annual bottom temperature in the Celtic Sea) and 391.07 +/- 0.05 ppm atmospheric [CO<sub>2</sub>]. Aquaria receiving an environment representative of future climate conditions were held at ambient+4 degrees C (14.56 +/- 0.20 degrees C) and 1026 +/- 0.24 ppm atmospheric [CO<sub>2</sub>]. Levels of [CO<sub>2</sub>] were controlled using a CO<sub>2</sub>-air mixing which maintained and monitored the supply of the air mixture to each aquarium using infrared gas analysers (Licor LI-840A, 1 per CO<sub>2</sub> treatment). After 6 months, luminophores, coloured sand (pink) which fluoresces under ultra-violet light, were added to assess bioturbation. The mesocosms were then inoculated with sodium bromide to enable bioirrigation analysis. Sediments were analysed for pH, temperature, salinity, alkalinity and inorganic nutrients (ammonium (NH<sub>4</sub>-N), nitrite + nitrate (NO<sub>x</sub>-N) and phosphate (PO<sub>4</sub>-P)), bicarbonate (H<sub>2</sub>CO<sub>3</sub><sup>-</sup>), carbonate (CO<sub>3</sub><sup>2-</sup>) and pCO<sub>2</sub>, particle size, percentage organic carbon content, faunal mediated sediment particle reworking and faunal abundance, biomass and functional trait composition. The data were collected as part of the Shelf Sea Biogeochemistry (SSB) research programme as part of the Biogeochemistry, Macronutrient and Carbon Cycling in the benthic layer (BMCC) research programme. SSB was co-funded by the Natural Environment Research Council (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.