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Dale, Andy W; Sommer, Stefan; Ryabenko, Evgenia; Noffke, Anna; Bohlen, Lisa; Wallmann, Klaus; Stolpovsky, Konstantin; Greinert, Jens; Pfannkuche, Olaf (2014): Porewater and particulate geochemistry during Maria S. Merian cruise MSM17/4. PANGAEA, https://doi.org/10.1594/PANGAEA.835700, Supplement to: Dale, AW et al. (2014): Benthic nitrogen fluxes and fractionation of nitrate in the Mauritanian oxygen minimum zone (Eastern Tropical North Atlantic). Geochimica et Cosmochimica Acta, 134, 234-256, https://doi.org/10.1016/j.gca.2014.02.026

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Abstract:
We present sedimentary geochemical data and in situ benthic flux measurements of dissolved inorganic nitrogen (DIN: NO3-, NO2-, NH4+) and oxygen (O2) from 7 sites with variable sand content along 18°N offshore Mauritania (NW Africa). Bottom water O2 concentrations at the shallowest station were hypoxic (42 µM) and increased to 125 µM at the deepest site (1113 m). Total oxygen uptake rates were highest on the shelf (-10.3 mmol O2 /m2 d) and decreased quasi-exponentially with water depth to -3.2 mmol O2 /m2 d. Average denitrification rates estimated from a flux balance decreased with water depth from 2.2 to 0.2 mmol N /m2 d. Overall, the sediments acted as net sink for DIN. Observed increases in delta 15NNO3 and delta 18ONO3 in the benthic chamber deployed on the shelf, characterized by muddy sand, were used to calculate apparent benthic nitrate fractionation factors of 8.0 pro mille (15epsilon app) and 14.1 pro mille (18epsilon app). Measurements of delta 15NNO2 further demonstrated that the sediments acted as a source of 15N depleted NO2-. These observations were analyzed using an isotope box model that considered denitrification and nitrification of NH4+ and NO2-. The principal findings were that (i) net benthic 14N/15N fractionation (epsilon DEN) was 12.9 ± 1.7pro mille, (ii) inverse fractionation during nitrite oxidation leads to an efflux of isotopically light NO2- (-22 ± 1.9 pro mille), and (iii) direct coupling between nitrification and denitrification in the sediment is negligible. Previously reported epsilon DEN for fine-grained sediments are much lower (4-8 pro mille). We speculate that high benthic nitrate fractionation is driven by a combination of enhanced porewater-seawater exchange in permeable sediments and the hypoxic, high productivity environment. Although not without uncertainties, the results presented could have important implications for understanding the current state of the marine N cycle.
Related to:
Pfannkuche, Olaf (2014): Climate-Biogeochemistry interactions in the tropical ocean of the NW-African oxygen minimum zone (SFB754) - Cruise No. MSM17/4 - March 10 - April 11, 2011 - Dakar (Senegal) - Las Palmas (Spain). MARIA S. MERIAN-Berichte, DFG-Senatskommission für Ozeanographie, MSM17/4, 59 pp, https://doi.org/10.2312/cr_msm17_4
Further details:
Funding:
German Science Foundation (DFG), grant/award no. 27542298: Climate - Biogeochemistry Interactions in the Tropical Ocean
Coverage:
Median Latitude: 17.354804 * Median Longitude: -16.766043 * South-bound Latitude: 12.389170 * West-bound Longitude: -18.533420 * North-bound Latitude: 18.288320 * East-bound Longitude: -16.316770
Date/Time Start: 2011-03-13T15:09:00 * Date/Time End: 2011-04-08T10:23:00
Size:
57 datasets

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Datasets listed in this publication series

  1. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_330. https://doi.org/10.1594/PANGAEA.835613
  2. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_330. https://doi.org/10.1594/PANGAEA.835616
  3. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_335. https://doi.org/10.1594/PANGAEA.835670
  4. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_335. https://doi.org/10.1594/PANGAEA.835647
  5. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_342. https://doi.org/10.1594/PANGAEA.835671
  6. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_353. https://doi.org/10.1594/PANGAEA.835672
  7. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_353. https://doi.org/10.1594/PANGAEA.835648
  8. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_366. https://doi.org/10.1594/PANGAEA.835673
  9. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_366. https://doi.org/10.1594/PANGAEA.835649
  10. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_378. https://doi.org/10.1594/PANGAEA.835674
  11. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_378. https://doi.org/10.1594/PANGAEA.835650
  12. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_406. https://doi.org/10.1594/PANGAEA.835675
  13. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_406. https://doi.org/10.1594/PANGAEA.835651
  14. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_421. https://doi.org/10.1594/PANGAEA.835676
  15. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_421. https://doi.org/10.1594/PANGAEA.835652
  16. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_425. https://doi.org/10.1594/PANGAEA.835677
  17. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_425. https://doi.org/10.1594/PANGAEA.835653
  18. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Geochemistry at BIGO station MSM17/4_425 on given timesteps. https://doi.org/10.1594/PANGAEA.835618
  19. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_438. https://doi.org/10.1594/PANGAEA.835678
  20. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_438. https://doi.org/10.1594/PANGAEA.835654
  21. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Geochemistry at BIGO station MSM17/4_438 on given timesteps. https://doi.org/10.1594/PANGAEA.835694
  22. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_448. https://doi.org/10.1594/PANGAEA.835679
  23. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_448. https://doi.org/10.1594/PANGAEA.835655
  24. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_453. https://doi.org/10.1594/PANGAEA.835680
  25. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_453. https://doi.org/10.1594/PANGAEA.835656
  26. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Geochemistry at BIGO station MSM17/4_453 on given timesteps. https://doi.org/10.1594/PANGAEA.835695
  27. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_463. https://doi.org/10.1594/PANGAEA.835681
  28. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_463. https://doi.org/10.1594/PANGAEA.835657
  29. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_466. https://doi.org/10.1594/PANGAEA.835682
  30. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_466. https://doi.org/10.1594/PANGAEA.835658
  31. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Geochemistry at BIGO station MSM17/4_466 on given timesteps. https://doi.org/10.1594/PANGAEA.835696
  32. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_483. https://doi.org/10.1594/PANGAEA.835683
  33. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_483. https://doi.org/10.1594/PANGAEA.835659
  34. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_485. https://doi.org/10.1594/PANGAEA.835684
  35. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_485. https://doi.org/10.1594/PANGAEA.835660
  36. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Geochemistry at BIGO station MSM17/4_485 on given timesteps. https://doi.org/10.1594/PANGAEA.835713
  37. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_494. https://doi.org/10.1594/PANGAEA.835685
  38. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_494. https://doi.org/10.1594/PANGAEA.835661
  39. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Geochemistry at BIGO station MSM17/4_494 on given timesteps. https://doi.org/10.1594/PANGAEA.835697
  40. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_506. https://doi.org/10.1594/PANGAEA.835686
  41. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_506. https://doi.org/10.1594/PANGAEA.835662
  42. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_521. https://doi.org/10.1594/PANGAEA.835687
  43. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_521. https://doi.org/10.1594/PANGAEA.835663
  44. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_528. https://doi.org/10.1594/PANGAEA.835688
  45. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_528. https://doi.org/10.1594/PANGAEA.835664
  46. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_530. https://doi.org/10.1594/PANGAEA.835689
  47. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_530. https://doi.org/10.1594/PANGAEA.835665
  48. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Geochemistry at BIGO station MSM17/4_530 on given timesteps. https://doi.org/10.1594/PANGAEA.835698
  49. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_536. https://doi.org/10.1594/PANGAEA.835690
  50. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_536. https://doi.org/10.1594/PANGAEA.835666
  51. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_539. https://doi.org/10.1594/PANGAEA.835691
  52. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_539. https://doi.org/10.1594/PANGAEA.835667
  53. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Geochemistry at BIGO station MSM17/4_539 on given timesteps. https://doi.org/10.1594/PANGAEA.835699
  54. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_560. https://doi.org/10.1594/PANGAEA.835692
  55. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_560. https://doi.org/10.1594/PANGAEA.835668
  56. Dale, AW; Domeyer, B; Sommer, S (2014): Particulate geochemistry of sediment core MSM17/4_584. https://doi.org/10.1594/PANGAEA.835693
  57. Dale, AW; Domeyer, B; Surberg, R et al. (2014): Porewater geochemistry of sediment core MSM17/4_584. https://doi.org/10.1594/PANGAEA.835669