Bermuda Atlantic Time Series site, DY084/085 cruise track from Southampton, UK to Stanley, Falkland Islands

Particulate total and organic carbon concentrations in the water column; Particulate total and organic nitrogen concentrations in the water column; Phosphate concentration parameters in the water column; Nitrate concentration parameters in the water column; Ammonium and ammonia concentration parameters in water bodies; Nitrification and denitrification rates in water bodies; Regenerated production in water bodies; Silicate concentration parameters in the water column; Nitrite concentration parameters in the water column; Experiment state variables

Autoanalysers; isotope ratio mass spectrometers; CTD; shipboard incubators

This data set consists of nitrogen and carbon (including nitrogen and carbon fluxes), and nutrient (Nitrite, Nitrate+Nitrite, Silicate, Phosphate and Urea) incubation data, as well as vertical nutrient profiles. The samples for incubation were collected from the Bermuda Atlantic Time Series (BATS) site (31.667 °N, 64.1667 °W), as well as discrete locations in the Atlantic Ocean during RRS Discovery cruise DY084/085, which sailed between Southampton, UK and Stanley, Falkland Islands. The BATS site was visited 4 times, once each in April, July, and November 2016, and once in April 2017. The Discovery cruise took place between September and November 2017. CTD Niskin rosettes were deployed from the ships at the BATS site and at 11 locations during the DY084/085 cruise to collect water samples for the incubation experiments. At each sampling station, 4-6 depths were chosen and 4.5 L of water subsamples were amended with 15N-labeled ammonium, nitrate, amino acids, urea, dissolved organics and particulate algal matter. Throughout the 28-hour incubation period, 5 subsamples were collected at subsequent time intervals for the following analyses: nitrogen stable isotopes and d15N-ammonium, using a gas chromatography isotope ratio mass spectrometer (GC-IRMS); ammonium, using the standard fluorometric method; and nutrient (nitrite, nitrate, silicate and phosphate) and urea, following spectrophotometric methods, the former was conducted with a nutrient autoanalyser. The last subsample also served for isotopic analyses of particulate organic nitrogen and carbon (PON & POC), also using a GC-IRMS. The vertical nutrient profiles are described from samples taken from CTD bottles deployed during the routine CTD casts on the DY084/085 cruise. 11 stations were sampled, the same as for the incubation water. Analyses followed the same spectrophotometric methods and also involved a nutrient autoanalyser. This data set aims to improve knowledge on the characterisation of the mechanisms of N-remineralisation and the rate measurements of this process in the mesopelagic (100 – 1000 m). The cruise locations were chosen in order to examine N-remineralisation in diverse nutrient regimes, while temporal variability was explored via the seasonal sampling at the BATS site. This data set was created under NERC grant NE/N003187/1, titled “Shortcuts in the Oceanic Nitrogen Cycle: Fluxes and Microbial Pathways of Nitrogen Remineralization in the Ocean's Twilight Zone”, held at the School of Ocean and Earth Science at the University of Southampton.

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