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The biological response to in situ Southern Ocean iron fertilization.

SOFeX: Southern Ocean Iron Experiments, An Overview of the Biological Responses. The biological response to in situ Southern Ocean iron fertilization. Richard T. Barber and SOFeX Team. Richard Barber and the SOFeX Group.

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The biological response to in situ Southern Ocean iron fertilization.

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  1. SOFeX: Southern Ocean Iron Experiments, An Overview of the Biological Responses The biological response to in situ Southern Ocean iron fertilization. Richard T. Barber and SOFeX Team Richard Barber and the SOFeX Group

  2. Primary productivity, photosynthetic performance and quantum yield team on the three ships: R/V Revelle: Barber, Lance, Stuebe R/V Melville: Hilting, Hiscock, Apprill, Delizo, Tanner USCG Polar Star: Van Hilst FRRF data provided by Sasha Tozzi. PAM data provided by Jill Peloquin. POC flux data provided by Ken Buesseler.

  3. North Patch Temp. 7.5ºC Si(OH)4 2.0μM NO3 21μM +Fe 1.2nM South Patch Temp. -0.5ºC Si(OH)4 63μM NO3 27μM +Fe 0.7nM

  4. SP NP Underway nutrients and temperature figure provided by W. T. Hiscock, U. Miami.

  5. SOFeX Productivity DUKE - MBARI - VIMS - SIO South Patch 4 Melville Revelle Fertilization Polar Star 3 2 Surface Chl (mg Chl m-3) 1 0 20 25 30 35 40 45 50 55 Year Day

  6. South Patch Melville Revelle Fertilization 4 3 Popt (mmolC m-3 d-1) 2 1 0 20 25 30 35 40 45 50 55 Year Day SOFeX Productivity DUKE - MBARI - VIMS - SIO

  7. 1 2 3 4 5 6 7 1 2 3 4 5 6 7 0 20 40 60 80 100 North Out North In 120 140 160 Initial "Pre" PP profile Earliest "In" PP profile Final "Out" PP profile Final "In" PP profile 0 20 40 South Out South In 60 80 0.5 1.0 1.5 2.0 2.5 3.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 -3 -1 Prim. Prod. GF/F (mmol C m d ) Zmorel (m) Zmorel (m)

  8. No. Patch revisit by Revelle.

  9. Melville Revelle Fertilization SOFeX Productivity DUKE - MBARI - VIMS - SIO North Patch 3.0 2.5 2.0 1.5 Surface Chl (mg Chl m-3) 1.0 0.5 0.0 10 15 20 25 30 35 40 45 50 Year Day

  10. North Patch Melville Revelle 7 Fertilization 6 5 Popt (mmolC m-3 d-1) 4 3 2 1 0 10 15 20 25 30 35 40 45 50 Year Day SOFeX Productivity DUKE - MBARI - VIMS - SIO

  11. Out 10% 40 In 10% 30 Binned Int PP (mmol C m-2 d-1) 20 10 1 2 3 Weeks Post First Fertilization

  12. Outs PAM- bulk assemblage for South Patch, bars are iron additions, circled data are OUTs. Cells never reached photochemical maximum for 20 m water for PAM (0.70).

  13. Results • 10x increase in Chl in both N and S patch • 10x increase in productivity (Popt) in both N and S patch • 3 to 4x increase in integrated primary productivity • 3 to 4x increase in quantum yield in South patch, but no differential enhancement of quantum yield in large (> 20 μm) phytoplankton • Big change in size composition in N patch despite low Si conditions, but only modest change in size composition in S patch with high Si conditions • In patch POC flux about 30% of In patch PP integrated to 10% light level; Out flux about 40% of Out PP integrated to 10% light level

  14. Remaining Questions • Depth of export • Fate of exported organic carbon at depth • Cellular mechanism of “fast” photosynthetic efficiency response to Fe • Nature of temperature vs. photosynthetic efficiency relationship

  15. South Patch Melville 80 Revelle Fertilization 70 60 50 % Popt >20 μm 40 30 20 10 0 20 25 30 35 40 45 50 55 Year Day SOFeX Productivity DUKE - MBARI - VIMS - SIO

  16. Prim Prod (mmol C m-3 d-1)

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