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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,

Published byEthelbert Dixon Modified over 8 years ago

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Presentation on theme: "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,"— Presentation transcript:

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 NH 4 + is preferred N nutrient

3 Marine N Non-bioavailable N 2 O 200 Tg N (+1) N 2 2.2*10 7 Tg N (0) Bioavailable/Fixed (oxidation state) NO 3 - 5.7*10 5 Tg N (+5) NO 2 - 500 Tg N (+3) NH 4 + 7.0*10 3 Tg N (-3) Organic N 5.3*10 5 Tg N (-3) Libes, 1992 Nitrate Nitrite Ammonia

4 Marine Reservoir: 6.3*10 5 Tg N Sources: 287 Tg N/yr Atmospheric deposition: 86 Tg N/yr N 2 fixation: 125 Tg N/yr River Input: 76 Tg N/yr Codispoti et al. (2001) Marine Fixed N Budget

5 Marine Reservoir: 6.3*10 5 Tg N Sources: 287 Tg N/yr Sinks: 482 Tg N/yr Water Column denitrification: 150 Tg N/yr Atmospheric deposition: 86 Tg N/yr N 2 O loss: 6 Tg N/yr N 2 fixation: 125 Tg N/yr Sedimentation: 25 Tg N/yr Benthic denitrification: 300 Tg N/yr Organic N export: 1 Tg N/yr River Input: 76 Tg N/yr Codispoti et al. (2001) Marine Fixed N Budget

6 Marine Reservoir: 6.3*10 5 Tg N Sources: 287 Tg N/yr Sinks: 482 Tg N/yr Water Column denitrification: 150 Tg N/yr Atmospheric deposition: 86 Tg N/yr N 2 O loss: 6 Tg N/yr N 2 fixation: 125 Tg N/yr Sedimentation: 25 Tg N/yr Benthic denitrification: 300 Tg N/yr Organic N export: 1 Tg N/yr River Input: 76 Tg N/yr Codispoti et al. (2001) Marine Fixed N Budget

7 Oceanic Nitrogen Budget Estimates Georgia Tech Biological Oceanography

8 N* Distribution Shows Interplay Between N 2 -Fixation and Denitrification N* = 0.87( [NO 3 - ] - 16[PO 4 3- ] + 2.9) (Gruber & Sarmiento 1997)

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. Georgia Tech Biological Oceanography Trichodesmium puffs (above) and tufts (right). Photos by Hans Paerl. Trichodesmium blooms from aboard ship (left) and from space (below).

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

11 NO 3 Chlorophyll Large detritus Organic matter N2N2 NH 4 NO 3 Water column Sediment Phytoplankton NH 4 Mineralization Uptake Nitrification Grazing Mortality Zooplankton Susp. particles Aerobic mineralization Denitrification N2N2 Fixation Mix Layer depth Oceanic N Cycle Schematic

12 NH 4 + New vs. Regenerated Production Biological Pump

13 Respiration ΔG° (kJ/mol) -119 Denitrification -113 MnO 2 reduction -96.9 Fe oxide reduction -46.7 Sulfate reduction -20.5 Methanogenesis -17.7 Organic Matter Oxidation Sequence Morel & Herring, 1993

14 Beggiatoa Mat Overview Georgia Tech Biological Oceanography

15 Beggiatoa Mat Georgia Tech Biological Oceanography

16 Alternative pathways to N 2 NitrificationAnammox OLAND MnO 2 Reduction Microbially mediated Chemical Reactions Heterotrophic Denitrification Nitrogen Fixation Mn 2+ Oxidation

17 Microbial Community Processes Georgia Tech Biological Oceanography

18 Alternative Pathways to N 2

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

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