YagerDOE2005

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Published on September 17, 2007

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The impact of nitrogen fixation on carbon sequestration: a reassessment of the inorganic carbon system in LNLC regions:  The impact of nitrogen fixation on carbon sequestration: a reassessment of the inorganic carbon system in LNLC regions Patricia L. Yager University of Georgia School of Marine Programs 05/26/05 DOE Workshop, Belmont, MD Conclusion:  Conclusion As we debate the potential costs and benefits of iron fertilization to carbon sequestration, realize that we are already doing it in the tropical and subtropical oligotrophic oceans (albeit indirectly). 05/26/05 DOE Workshop, Belmont, MD Acknowledgments:  Acknowledgments Collaborators: Sarah Cooley (UGA) Doug Capone (USC) Ajit Subramaniam (LDEO) Victoria Coales (HPL) Tony Michaels (USC) Ed Carpenter (Romberg) NSF Biocomplexity Team Funding sources: DOE C-sequestration NOAA OGP GCC NASA ESS University of Georgia NSF Biocomplexity 05/26/05 DOE Workshop, Belmont, MD Slide4:  N2-supported new production (Lee et al., 2002) mol C m-2 y-1 Hood et al., 2000 'only the sinking flux due to new production associated with nitrogen fixation and nutrient inputs from terrestrial and atmospheric sources can be identified as biologically-mediated transport of atmospheric CO2 to the deep ocean' -Eppley and Peterson, Nature 1979 05/26/05 DOE Workshop, Belmont, MD Slide5:  Hemiaulus hauckii with endosymbionts Hemiaulus indicus with Richelia intracellularis Plus many other free-living or endosymbiotic cyanobacteria and Bacteria (Karl et al., Biogeochemistry, 2002 Trichodemsium Diazotrophs Courtesy of SERC Courtesy of R. Shipe Courtesy of P. Lundgren and B. Bergman 05/26/05 DOE Workshop, Belmont, MD Slide6:  http://web.uconn.edu/mcbstaff/benson/Frankia/N2fix.htm But here’s the catch: The nitrogenase enzyme needs iron 05/26/05 DOE Workshop, Belmont, MD Slide7:  Amazon River (looking south) (Tg y-1) Jickells et al. (Science 2005) Where does the iron going into the ocean come from? 05/26/05 DOE Workshop, Belmont, MD River fluxes sensitive to land use and hydrology (climate) Slide8:  The Amazon is one of the few rivers that impact the ocean beyond the continental shelf NASA SeaWIFS 05/26/05 DOE Workshop, Belmont, MD Slide9:  Dust from Africa Sensitive to climate and land use Max flux: May-Sept Deposition site depends on ITCZ Africa Brazil Africa 05/26/05 DOE Workshop, Belmont, MD Slide10:  Jickells et al. (Science 2005) 05/26/05 DOE Workshop, Belmont, MD Slide11:  'In order for a process to qualify as a sink for anthropogenic CO2 emissions, the flux of carbon must have increased relative to its pristine value.' -Smith and Mackenzie, 1991 05/26/05 DOE Workshop, Belmont, MD Slide12:  Long Term Variability of Barbados Dust: The Link to Climate Major El Niño events: 1972-73, 1982-83, 1986-87, 1991-92, 1997-98 NOAA-CIRES Climate Diagnostics Center Multivariate ENSO Index web site: http://www.cdc.noaa.gov/~kew/MEI/mei.html]. Monthly Means, 1965-1998 Lots of variability, generally coherent from year-to-year. Courtesy of J. M. Prospero (USGS dust workshop online: http://esp.cr.usgs.gov/info/dust/ ) Slide13:  What was the longer term rainfall history of the Soudano-Sahel and what are the implications for dust transport? Prospero andamp; Lamb Science 302: 1024 ‑ 1027, 2003. 7 November 2003 This period of extended drought and increased dust occurs at a time when the global warming trend has become most visible. CONCLUSION: drought in Africa over the past 30 years was unique in the 20th century – probably dust transport as well. Courtesy of J. M. Prospero (USGS dust workshop online: http://esp.cr.usgs.gov/info/dust/ ) Carbon sequestration hypotheses::  Carbon sequestration hypotheses: The input of iron associated with aeolian dust and riverine sources stimulates photosynthesis via enhanced nitrogen fixation (Biocomplexity Project). The enhanced productivity caused by N2 fixation yields greater export of biological carbon which, in turn, draws down the pCO2 of the surface ocean and increases oceanic uptake of atmospheric CO2 (This grant). 05/26/05 DOE Workshop, Belmont, MD Carbon research questions:  Carbon research questions Can we predict how indirect iron fertilization (sensitive to climate and other human activities) will help sequester CO2? Only if we understand system mechanistically 05/26/05 DOE Workshop, Belmont, MD Atlantic Cruise Tracks:  Atlantic Cruise Tracks MP 1 Jan-Feb 2001 MP3 June-August 2001 M/P 8 April - May 2003 MANTRA/PIRANA Biocomplexity 05/26/05 DOE Workshop, Belmont, MD Slide17:  MANTRA/PIRANA - MP02 - Pacific Cruise 1 - 4/9/2001-4/30/2001 MP05 - Pacific Cruise 2 - 6/25/2002-7/19/2002 MP06 - Pacific Cruise 3 - 9/22/2002-10/16/2002 MP09 - Pacific Cruise 4 - 7/13/2003-8/23/2003 The Subtropical Pacific 05/26/05 DOE Workshop, Belmont, MD Slide18:  Sample Precision: DIC: 0.95 µmol/kg ALK: 2.1 µmol/kg del13DIC: 0.15 pCO2: 1 µatm Inorganic carbon system DIC: SOMMA/coulometer ALK: potentiometric titration Underway pCO2: Equilibrator/LICOR del13C-DIC: GC/MS 05/26/05 DOE Workshop, Belmont, MD Slide19:  Location and Size of the Amazon River Plume Based on Monthly Climatologies of Satellite Derived K490 MP1 MP8 MP3 DelVecchio and Subramaniam, 2004 05/26/05 DOE Workshop, Belmont, MD Slide20:  ∆pCO2 (air-sea) (calculated from discrete DIC andamp; ALK surface samples) Cooley and Yager (JGR submitted) The river plume converts an oceanic source to a sink 05/26/05 DOE Workshop, Belmont, MD Slide21:  Winter Summer DIC ALK DIC ALK Depth profiles Summer data shows significantly lower concentrations at the surface due to presence of the river. Cooley and Yager (JGR submitted) 05/26/05 DOE Workshop, Belmont, MD The question is whether there is more or less than predicted by simple river dilution:  Z DIC Production Summer Winter Winter SML Expected Z Respiration Winter SML DIC Enhanced production? Or enhanced respiration? Summer Expected Winter The question is whether there is more or less than predicted by simple river dilution S.R. Cooley 05/26/05 DOE Workshop, Belmont, MD Slide23:  Cooley and Yager (JGR submitted) Alkalinity is conservative; DIC is not 05/26/05 DOE Workshop, Belmont, MD Slide24:  Biological/Physical Effects Mixing model calculates proportional contributions of plume, seawater (Assumes conservative TA, salinity) Calculate predicted DIC Compare predicted, observed DIC plume seawater observed 05/26/05 DOE Workshop, Belmont, MD Slide25:  Cooley and Yager (JGR submitted) Net community production? The difference between observed and that predicted from mixing alone Up to 1 mol C m-2 Would be underestimate if include gas exchange: (0-0.2 mol C m-2) 05/26/05 DOE Workshop, Belmont, MD Slide26:  Aerosol [Fe] clearly linked to ITCZ seasonality Dissolved [Fe] uncoupled from atm clearly linked to river Subramaniam et al. (Nature in review) Mean dry deposition of labile Fe: Winter: 0.24 µmol m-2 d-1) Spring: 0.09 µmol m-2 d-1) Summer: 0.06 µmol m-2 d-1) 05/26/05 DOE Workshop, Belmont, MD Slide27:  Subramaniam et al. (Nature in review) Tricho biomass linked to dust Richelia abundance clearly linked to river Subramaniam et al. (Nature in review) 05/26/05 DOE Workshop, Belmont, MD Slide28:  Subramaniam et al. (Nature in review) Depth integrated N2-fixation 05/26/05 DOE Workshop, Belmont, MD Slide29:  Subramaniam et al. (Nature in review) Biological carbon drawdown Carbon drawdown is dominated by diatom-endosymbionts. 05/26/05 DOE Workshop, Belmont, MD Slide30:  Trichodesmium Heterotrophic bacteria Diatoms with Richelia Grazers Picoplankton Phytoplankton community structure matters Subramaniam et al. (Nature in review) 05/26/05 DOE Workshop, Belmont, MD Slide31:  See also Deuser et al. (1988) Courtesy of A. Subramaniam 05/26/05 DOE Workshop, Belmont, MD Slide32:  Location and Size of the Amazon River Plume Based on Monthly Climatologies of Satellite Derived K490 MP1 MP8 MP3 DelVecchio andamp; Subramaniam, 2004 05/26/05 DOE Workshop, Belmont, MD Slide33:  Organic Carbon makes up 5-40% of Total Flux i.e. 5-40% of 150 mg/m2/d = 7.5-60 mg/m2/d Over the area of the Richelia habitat, this is 2 – 15 Tg C y-1 The global mean air-to-sea flux of carbon is 15 mg C/m2/day. Subramaniam et al. (Nature in review) 05/26/05 DOE Workshop, Belmont, MD Conclusions:  Conclusions Nitrogen fixation is clearly linked to iron fertilization. The enhanced production yields greater carbon sequestration when the community is dominated by the diatom-diazotroph symbionts found in the river plume. This mechanism, in the WTNA region alone, likely accounts for sequestration of up to 15 Tg C yr-1. 05/26/05 DOE Workshop, Belmont, MD Remaining questions:  Remaining questions Seasonal and interannual variability versus long-term change in iron flux? Cooley and Yager (GBC, in prep) Where does the 'export' go? Cooley and Yager (in prep): modeling Yager (in prep): isotope analysis Is this a globally significant phenomenon? MMAMBO to NSF DOE? 05/26/05 DOE Workshop, Belmont, MD Conclusion:  Conclusion As we debate the potential costs and benefits of iron fertilization to carbon sequestration, realize that we are already doing it in the tropical and subtropical oligotrophic oceans (albeit indirectly). 05/26/05 DOE Workshop, Belmont, MD Acknowledgments:  Acknowledgments Collaborators: Sarah Cooley (UGA) Doug Capone (USC) Ajit Subramaniam (LDEO) Victoria Coales (HPL) Tony Michaels (USC) Ed Carpenter (Romberg) NSF Biocomplexity Team Funding sources: DOE C-sequestration NOAA OGP GCC NASA ESS University of Georgia NSF Biocomplexity 05/26/05 DOE Workshop, Belmont, MD Slide38:  Sarah Cooley The Role of the Amazon Plume in the Western Tropical Atlantic Ocean Inorganic Carbon Budget 05/26/05 DOE Workshop, Belmont, MD

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