DOI: 10.5285/46ecc183-c08d-2211-e053-6c86abc0d02c
title: Community mediation on shelf-sea benthic nitrogen cycling following bottom trawling and organic enrichment.

description: This dataset contains data from mesocosm experiments with sediment cores to test the effects of fishing and organic enrichment on sediment biogeochemistry. The author has concerns about samples A10-37, A10-38, A10-40, A10-43, A2-65 used for particle size analysis. Percentage composition of different sediment fractions does not add up to 100% indicating some loss of different sediment fractions. Cores were collected on board the RV Prince Madog in the Irish Sea from the 23<sup>rd</sup>- 25<sup>th</sup> June 2015. The mesocosm experiment was conducted at the School of Ocean Sciences, Bangor University from the 26<sup>th</sup> June - 27<sup>th</sup> July 2015. Intact sediment cores (n = 40, 5 cores per treatment) with their associated fauna were collected using a 0.1 m<sup>2</sup> NIOZ (Netherlands Institute for Sea Research, Texel) corer from two fishing grounds, one on sand, the other on sandy mud. Two sediment subsamples were taken from each core; one for particle size and organic matter analysis (5 cm diameter x 5 cm deep sample) and another for the mesocosm experiment, measuring 20 cm (L) x 20 cm (W) x 12 cm (H). The latter was transferred to a Perspex aquarium, overlaid by ca. 20 cm (6.5 L) of ambient seawater and incubated in the dark in a constant temperature laboratory at 13 degrees centigrade (average sea bottom temperature at sampling sites during sampling period, 23-25<sup>th</sup>  June 2015) for a total duration of 1 month; a 15 day acclimatization period prior to the addition of organic matter and a 15 day experimental period following the addition of organic matter. Enriched treatments (n = 20) received 50 mL of a monoculture solution of the microalga Isochrysis galbana (concentration of ca. 22.22 cells uL<sup>-1</sup>) at the start of the experiment. Circulation of the overlying water within the cores was maintained by gentle bubbling with filtered air for the entire duration of the acclimatization and experimental periods. The experimental design consisted of 2 levels of fishing (levels: Low and High), 2 levels of organic enrichment (levels: Non-enriched, Non-En and Enriched, En) and 2 types of sediment (sand (S) and sandy mud (sM)). Effects on nitrogen cycling were measured through changes in the macroinfaunal and microbial community composition, the abundance of archaeal and bacterial nitrifiers and denitrifiers and changes in the concentration of dissolved inorganic nutrients in overlying water. The data were collected as part of the Shelf Sea Biogeochemistry (SSB) research programme as part of module 3, modified Task 3.2.2 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. Sample collection in the field carried out by Marija Sciberras and Jan Hiddink (School of Ocean Sciences, Bangor University). Sample collection during mesocosm experiment carried out by Marija Sciberras (School of Ocean Sciences, Bangor University). Particle size analysis (PSA) and organic matter content analysis, macro-infaunal processing and specimen identification was carried out by  Marija Sciberras (School of Ocean Sciences, Bangor University). Water nutrient concentration analysis was carried out by Malcolm Woodward (Plymouth Marine Laboratory). Microbial analysis was conducted by Karen Tait (Plymouth Marine Laboratory). The British Oceanographic Data Centre (BODC) created the metadata entry and is responsible for holding master copies of the data.