Description: Our data, as part of the OISO (Ocean Indien Service d'Observation) campaign, contributes to a better understanding of the physical and biological factors controlling N2 fixation in the Southern Indian Ocean and the French Southern and Antarctic lands during Austral summer January and February 2017. We measured N2 and C fixation as well as NH4+ and NO3- assimilation in 3-6 replicates per station. Additionally, we measured diagnostic pigment concentrations to evaluate phtosynthetic community composition. For pigment analysis 4L water was filtered through 25mm Whatman GF/F filters (pressure drop 〈10kPa). Samples were stored at -80°C until analysis. Pigments were analysed using High Performance Liquid Chromatography (HPLC). Pigment concentration were calculated according to Kilias et al (2013, doi:10.1111/jpy.12109). N2 fixation experiments were carried out in three to six replicates for each station. Incubations were done in pre-acid washed polycarbonate bottles on deck with ambient light conditions. All polycarbonate incubation bottles were rinsed with deionized water, and seawater prior to incubation. We used the combination of the bubble approach (Montoya et al., 1996) and the dissolution method (Mohr et al., 2010, doi:10.1371/journal.pone.0012583) proposed by Klawonn et al. (2015, doi:10.3389/fmicb.2015.00769). Bottles were filled up to capacity to avoid air contamination. Incubations were initialized by adding a 10 ml 15-15N gas bubble. Bottles were gently rocked for 15 minutes. Finally, the remaining bubble was removed to avoid equilibration between gas and aqueous phase. after 24 hours a water subsample was taken to a 12 ml exetainer and preserved with 100 µl HgCl2 solution for later determination of exact 15N-15N concentration. Natural 15N2 was determined using Membrane Inlet Mass Spectrometry (MIMS; GAM200, IPI) for each station. Analysis of 15N2 incorporated was carried out by the Isotopic Laboratory at the UC Davis, California campus. We used stable isotope tracers (15N) to measure dissolved inorganic nitrogen (DIN) assimilation rates. Experiments were initiated by adding a known concentration of 0.05 of K15NO3 and 15NH4Cl for oligotrophic waters of the IO and 0.625 µmol L-1 for HNLC regions in the ACC and PF (Knap et al., 1994, Waite et al., 2007, doi:10.1016/j.dsr2.2006.12.010) to one litre polycarbonate bottles. For C assimilation experiments, we added 20 µmol L-1 of NaH13CO3 to one of each of N2 fixation, NH4+ and NO3- assimilation experiment bottles. For incubation, we followed the same procedure as for N2 fixation experiments. Findings reveal that N2 fixation occurs throughout the whole sampling area up to 55°S latitude. In addition, variations of N2 fiaxation rates between replicates were relatively high indicating a great heterogeneity of the French Southern and Antarctic waters. References: Montoya 1996: Montoya, Joseph P., et al. "A Simple, High-Precision, High-Sensitivity Tracer Assay for N (inf2) Fixation." Applied and environmental microbiology 62.3 (1996): 986-993. Knap et al 1994: Knap, A., Michaels, A., Close, A., Ducklow, H. & Dickson, A. 1994. Protocols for the Joint Global Ocean Flux Study (JGOFS) Core Measurements, JGOFS, Reprint of the IOC Manuals and Guides No. 29. UNESCO, 19, 1.

Description: This data was collected as part of the Polarstern PS113 expedition to obtain insights into primary productivity on a latitudinal transect in the Atlantic Ocean. In-situ experiments of stable isotope (13C) uptake were conducted on board in triplicates of 1L pre-acid washed polycarbonate bottles. In detail, samples were spiked with Na13CO3 at a final 13C concentration of 200 µmol L-1. Experiments were terminated after 24h incubation and filter on a 0.7 precombusted polycarbonate filter. Samples were snap fronzen and stored at -80°C while at sea. Prior analysis, samples were acid fumed and dried. Samples were analysed on a PDZ Europa ANCA-GSL elemental analyzer interfaced to a PDZ Europa 20-20 isotope ratio mass spectrometer (Sercon Ltd., Cheshire, UK) by the Isotopic Laboratory at the UC Davis, California campus. This data reflects high-resolution spatial variations in primary productivity.

Description: This data set was collected in support of an investigation of the variability of particulate organic matter content and composition across a high-resoultion latitudinal transect across the Atlantic Ocean during the PS113 expedition. 4L of seawater from the clean ships' underway system were filtered on a 0.7 µm pre-combusted GFF filter. Samples were snap-frozen and stored at -80°C while at sea. Samples were acid fumed and dried before analyses. Particulate organic carbon and particulate nitrogen contents were measured using an Euro EA elemental analyzer (CHNS; EuroVector, Italy). This data reflects high-resolution spatial variabilites in particulate organic carbon and particulate nitrogen concentrations in surface waters accompanied by few samples from higher depths (0 - 400 m).

Description: This data was collected to investigate spatial differences in dissolved inorganic nutrient concentrations in surface waters of the Atlantic Ocean as part of the PS113 expedition. Water samples for dissolved inorganic nutrient concentrations including Nitrate, Silicate and Phosphate were filtered through a 0.2 µm syringe filter and stored at -80°C while at sea. Nutrient concentrations were assayed on an Evolution 3 Alliance Autoanalyser and calibrations were corrected for concentrations using certified reference material (CRM) 7602a (JAMSTEC; JAPAN) and MERCK STD (NIST-Standard). Concentrations were calculated by means of standard colorimetric techniques (Grasshoff, Kremling, & Ehrhardt, 2009).

Description: Climate change is opening the Arctic Ocean to increasing human impact and ecosystem changes. Arctic fjords, the region’s most productive ecosystems, are sustained by a diverse microbial community at the base of the food web. Here we show that Arctic fjords become more prokaryotic in the picoplankton (0.2–3 µm) with increasing water temperatures. Across 21 fjords, we found that Arctic fjords had proportionally more trophically diverse (autotrophic, mixotrophic, and heterotrophic) picoeukaryotes, while subarctic and temperate fjords had relatively more diverse prokaryotic trophic groups. Modeled oceanographic connectivity between fjords suggested that transport alone would create a smooth gradient in beta diversity largely following the North Atlantic Current and East Greenland Current. Deviations from this suggested that picoeukaryotes had some strong regional patterns in beta diversity that reduced the effect of oceanographic connectivity, while prokaryotes were mainly stopped in their dispersal if strong temperature differences between sites were present. Fjords located in high Arctic regions also generally had very low prokaryotic alpha diversity. Ultimately, warming of Arctic fjords could induce a fundamental shift from more trophic diverse eukaryotic- to prokaryotic-dominated communities, with profound implications for Arctic ecosystem dynamics including their productivity patterns.

Description: This paper explores the uptake processes that different communities use with regards to their standard operating procedures and best practices Across our five case studies, we noted what made uptake processes successful or challenging and distilled a set of recommendations to further develop the OBPS’s approach to supporting communities in developing and converging methods into best practices.