Nutrient data collected during the iMAR 2021/Eurofleets+ research cruise in Mid Atlantic Ridge (Azores EEZ)
|Temporal extent||2021-05-19 -2021-06-02|
|Author(s)||Mohn Christian4, Larsen Martin Mørk4, Evans Susan3, Neves De Sousa Laura2, Rodrigues Luis1, Dominguez-Carrió Carlos1, Taranto Gerald H.1, Carreiro-Silva Marina1, Morato Telmo1|
|Affiliation(s)||1 : Universidade dos Açores, Okeanos, Portugal
2 : Instituto Hidrográfico, Portugal
3 : National Oceanography Center, United Kingdom
4 : Aarhus University, Department of Ecoscience - Applied Marine Ecology and Modelling, Denmark
|Keyword(s)||Mid-Atlantic Ridge, Azores, Deep-sea, iMAR 2021, Eurofleets, Nutrients, Raw Data|
This dataset was produced during the iMAR cruise “The Integrated assessment of the distribution of Vulnerable Marine Ecosystem along the Mid-Atlantic Ridge (MAR) in the Azores region”, that took place aboard the Research Vessel Pelagia of the Royal Netherlands Institute for Sea Research between May 18th and June 2nd 2021. The iMAR cruise aimed to evaluate the role of the MAR in shaping latitudinal and trans-Atlantic patterns in deep-sea biogeography, connectivity and assemblages of deep-sea megafauna. This expedition was funded by the SEA OCEANS program of Eurofleets+ and the H2020 European project iAtlantic, and was led by the University of the Azores (Portugal) in collaboration with the Hydrographic Institute and University of Porto (Portugal), the University of Aarhus (Denmark), the National Oceanography Center (United Kingdom), GEOMAR (Germany), the University Museum of Bergen (Norway), the PP Shirshov Institute of Oceanology (Russia), and the University of Vale do Itajaí (Brazil).
Nutrient analysis was performed according to Grasshoff et al, adopted for a 5 channel continues flow analyzer (Skalar San Plus, Skalar Analytical B. V., Breda, The Netherlands). Nitrite and nitrate+nitrite was measured using an ammonia buffer and sulfanilamide/alpha-Naphthylethylene diamine dihydrochloride colour reagent in phosphoric acid, with reduction of nitrate to nitrite by cadmium column of at least 80% measured reduction capacity (90-100% achieved), followed by quantification with spectrophotometric determination of the nitrite-azo dye at 540 nm. Nitrate was determined as the difference between nitrate+nitrite and nitrite measurements. Ammonia was measured using a citrate/tartrate buffer and phenol color reagent, catalyzed by hypochlorite and nitroprusside , followed by quantification with spectrophotometric determination of the phenol-ammonia complex at 630 nm. Phosphate samples reacted with antimo nytartrate and ammonium molybdate solution in sulfuric acidified solution, the resulting complex wasreduced by ascorbic acid to a deep blue dye, followed by quantification with spectrophotometric determination of the reduced antimony-phospho-molybdate complex at 880 nm. Silicate samples was acidified with sulfuric acid and reacted with ammonium molybdate solution, reduced by ascorbic acid to a blue dye with oxalic acid to remove phosphate interference , followed by quantification with spectrophotometric determination of the reduced molybdo-silicate complex at 810 nm.
Methods used are accredited with expected detection limit of 0,04 µM for nitrite, 0,1 µM for nitrate, 0,3 µM for ammonia, 0,06 µM for Phosphate and 0,2 µM for silicate, with expected RSD between 4 and 7%for the individual nutrients.
Certified reference materials (VKI type QC RW1 for ammonia, phosphate and nitrate) and internal reference materials for Nitrite and silicate was spiked at two levels to natural low nutrient seawater sample for quality assurance, recovering 91-109% of the spike for nitrite, nitrate, phosphate and silicate at with RSD% of 1 to 5%, and recovery of 84-91% for ammonia, with RSDs up to 15%. No corrections was performed on data the recoveries. Except for ammonia, all results was within the acceptance limits for accredited analysis. Analysis was performed over two runs, one with triplicates and then a fourth spare sample was included to investigate the ammonia instability, but it could not be determined if this was due to storage/transport or instrument
The “.CSV” files of fully processed data contain data collected mainly in the North portion of the MAR in the Exclusive Economic Zone around the Azores.
|Acknowledgements||This research cruise contributes to the overarching scientific mission statement of the Azores Deep-sea research group at the Okeanos research centre of the University of the Azores: Deepen our understanding of the natural diversity, ecosystem structure, function, connectivity and resilience of deep-sea communities in the Azores EEZ in a changing planet, while informing a sustainable use of natural resources for current and future generations. RV Pelagia ship-time was provided free of charge for the iMAR survey, as part of a project which received funding from the European Union’s H2020 Research & Innovation Programme under grant agreement No. 824077 (EUROFLEETS+). We would like to thank the Royal Netherlands Institute for Sea Research (NIOZ) for making the RV Pelagia available to Eurofleets+ and to our team in particular. The Azores Deep-sea research group is funded by the European Union’s Horizon 2020 (H2020) programme under grant agreement No 678760 (ATLAS), No 689518 (MERCES) and No 818123 (iAtlantic), by the Fundação para a Ciência e Tecnologia (FCT) under the plurennial strategic project (UIDB/05634/2020) granted to Okeanos, the Program Stimulus of Scientific Employment (CCCIND/03345/2020 and CCCIND/03346/2020) and the PhD grant (PD/BD/111953/2015), by the Azores Government and PO2020 Açores under the MapGES (Acores-01-0145-FEDER-000056) and DeepWalls (ACORES-01-0145-FEDER-000124) projects as well as the PhD grant (M3.1.a/F/052/2015). We would like to thank the captain and crew of the RV Pelagia for their committed work during the whole iMAR cruise.|