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N cycling in the world’s oceans

N cycling in the world’s oceans. Nitrogen. N is an essential nutrient for all living organisms (nucleic acids and amino acids) N has many oxidation states, which makes speciation and redox chemistry very interesting NH 4 + is preferred N nutrient. Marine N. Libes, 1992. Non-bioavailable

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N cycling in the world’s oceans

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  1. N cycling in the world’s oceans

  2. Nitrogen • N is an essential nutrient for all living organisms (nucleic acids and amino acids) • N has many oxidation states, which makes speciation and redox chemistry very interesting • NH4+ is preferred N nutrient

  3. Marine N Libes, 1992 Non-bioavailable N2O 200 Tg N (+1) N2 2.2*107 Tg N (0) Bioavailable/Fixed (oxidation state) NO3- 5.7*105 Tg N (+5) NO2- 500 Tg N (+3) NH4+ 7.0*103 Tg N (-3) Organic N 5.3*105 Tg N (-3) Nitrate Nitrite Ammonia

  4. Marine Fixed N Budget Codispoti et al. (2001) Marine Reservoir: 6.3*105 Tg N Sources: 287 Tg N/yr Atmospheric deposition: 86 Tg N/yr N2 fixation: 125 Tg N/yr River Input: 76 Tg N/yr

  5. Marine Fixed N Budget Codispoti et al. (2001) Marine Reservoir: 6.3*105 Tg N Sources: 287 Tg N/yr Sinks: 482 Tg N/yr Atmospheric deposition: 86 Tg N/yr N2 fixation: 125 Tg N/yr N2O loss: 6 Tg N/yr Water Column denitrification: 150 Tg N/yr River Input: 76 Tg N/yr Organic N export: 1 Tg N/yr Benthic denitrification: 300 Tg N/yr Sedimentation: 25 Tg N/yr

  6. Marine Fixed N Budget Codispoti et al. (2001) Marine Reservoir: 6.3*105 Tg N Sources: 287 Tg N/yr Sinks: 482 Tg N/yr Atmospheric deposition: 86 Tg N/yr N2 fixation: 125 Tg N/yr N2O loss: 6 Tg N/yr Water Column denitrification: 150 Tg N/yr River Input: 76 Tg N/yr Organic N export: 1 Tg N/yr Benthic denitrification: 300 Tg N/yr Sedimentation: 25 Tg N/yr

  7. Oceanic Nitrogen Budget Estimates Georgia Tech Biological Oceanography

  8. N* Distribution Shows Interplay Between N2-Fixation and Denitrification N* = 0.87( [NO3-] - 16[PO43-] + 2.9) (Gruber & Sarmiento 1997) Georgia Tech Biological Oceanography

  9. Trichodesmium: The Usual Suspect • Diazotrophs, including Trichodesmium, are broadly distributed in nutrient poor oceanic waters, but their contribution to the marine N budget remains poorly constrained. Trichodesmiumblooms from aboard ship (left) and from space (below). Trichodesmium puffs (above) and tufts (right). Photos by Hans Paerl. Georgia Tech Biological Oceanography

  10. Major Biological Transformations of Nitrogen (Inspired by Codispoti 2001and Liu 1979) Georgia Tech Biological Oceanography

  11. Oceanic N Cycle Schematic Fixation N2 Nitrification Mineralization NH4 NO3 Uptake Phytoplankton Grazing Mix Layer depth Chlorophyll Zooplankton Mortality Large detritus Water column Susp. particles Nitrification N2 NH4 NO3 Denitrification Aerobic mineralization Organic matter Sediment

  12. Biological Pump NH4+ New vs. Regenerated Production

  13. Organic Matter Oxidation Sequence Morel & Herring, 1993 Respiration ΔG° (kJ/mol) -119 Denitrification -113 MnO2 reduction -96.9 Fe oxide reduction -46.7 Sulfate reduction -20.5 Methanogenesis -17.7

  14. Beggiatoa Mat Overview Georgia Tech Biological Oceanography

  15. Beggiatoa Mat Georgia Tech Biological Oceanography

  16. Alternative pathways to N2 Microbially mediated Nitrification Anammox Heterotrophic Denitrification OLAND Nitrogen Fixation Chemical Reactions MnO2 Reduction Mn2+ Oxidation

  17. Microbial Community Processes Georgia Tech Biological Oceanography

  18. Alternative Pathways to N2 Georgia Tech Biological Oceanography

  19. Surface Nutrient Distribution Data: eWOCE. Plot prepared with ODV

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