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Lynn Abramson 1* , Cindy Lee 1 , Stuart G. Wakeham 2 , J. Kirk Cochran 1 , and Robert Aller 1

Organic Composition of Particulate Organic Matter: Implications for the Exchange of Material Between Suspended and Sinking Particles. Lynn Abramson 1* , Cindy Lee 1 , Stuart G. Wakeham 2 , J. Kirk Cochran 1 , and Robert Aller 1

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Lynn Abramson 1* , Cindy Lee 1 , Stuart G. Wakeham 2 , J. Kirk Cochran 1 , and Robert Aller 1

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  1. Organic Composition ofParticulate Organic Matter: Implications for the Exchange of Material Between Suspended and Sinking Particles Lynn Abramson1*, Cindy Lee1, Stuart G. Wakeham2, J. Kirk Cochran1, and Robert Aller1 1. Marine Sciences Research Center, Stony Brook University, Stony Brook, NY 2. Skidaway Institute of Oceanography, Savannah, GA *Lynn.Abramson@msrc.sunysb.edu

  2. Organic Matter Composition POM composition reflects: • Source • Alteration • Exchange among pools

  3. Extent of Degradation Surface Slowly-sinking Fast-sinking 200m ? Depth 800m 1500m • Source & alteration can be revealed by biomarkers • Exchange can be revealed by compositional differences among pools of POM (e.g., pools separated by settling velocity)

  4. Methods • MedFlux Project • DYFAMED site, NW Mediterranean Sea • Spring (Mar.-May) & Summer (May-Jul.) 2003 • Sampled with IRS sediment traps & in situ pumps • Analyzed amino acids & pigments by HPLC

  5. Trap Pump Particle Types • “Suspended” Particles: Pumps • small particles (< 70 µm), with very slow settling velocities • “Sinking” Particles: Traps • Time Series mode: collect bulk sinking material at different depths (benchmark approach) • Settling Velocity mode: collect range of settling velocities

  6. Pumps 3/1 3/21 4/10 4/30 5/20 6/9 6/29 7/19 2003 3/1 3/21 4/10 4/30 5/20 6/9 6/29 7/19 2003 Overview of Conditions

  7. Pigment Composition (%) Amino Acid Composition (%) diatom SiO2 CaCO3 Depth (m) deg. deg. FP Composition with Depth:Early Spring 2003 (Mar. 4 – 11) *TR= time series traps; rest are pumps

  8. Pigment Composition (%) Amino Acid Composition (%) diatom SiO2 CaCO3 Depth (m) deg. deg. FP Composition with Depth:Late Spring 2003 (Apr. 30 – May 12) *TR= time series traps; rest are pumps

  9. Pigment Composition (%) Amino Acid Composition (%) diatom SiO2 FP Depth (m) CaCO3 deg. deg. Composition with Depth:Summer 2003 (Jun. 25 – 30) *TR= time series traps; rest are pumps

  10. Pigments Amino Acids diatom SiO2 FP % Composition CaCO3 deg. deg. Settling Velocity (m*d-1) Settling Velocity (m*d-1) Composition with Settling Velocity:Spring 2003 (Mar. 4 – May 12) *P= 200 m pumps; rest are 200 m settling velocity traps

  11. Pigments Amino Acids diatom deg. deg. FP % Composition SiO2 CaCO3 Settling Velocity (m*d-1) Settling Velocity (m*d-1) Composition with Settling Velocity:Summer 2003 (Jun. 25 – 30) *P= 200 m pumps; rest are 200 m settling velocity traps

  12. Early Spring (Mar.) Pumps Late Spring (May) Pumps Summer (Jun.) Pumps Spring (Mar.-May) 200m SV Trap Summer (May-Jun.) 200m SV Trap Numbers represent depths (pumps) or settling velocities (traps) Traps PC 2 (17%) direction of alteration Pumps PC 1 (32.9%) Composition with Settling Velocity *variable loadings scaled up 10x to fit axes

  13. Spring (Mar.-May) 200m SV Trap Summer (May-Jun.) 200m SV Trap Fresh & BCaCO3 Bacterial settling velocity settling velocity PC 2 (26%) PC 2 (20.5%) Bacterial, Fecal Pellets, & BSi BSi, BCaCO3,Fresh, & Fecal Pellets PC 1 (36.7%) PC 1 (41.6%) Composition with Settling Velocity *variable loadings scaled up 10x to fit axes

  14. Conclusions • Spring: compositional differences indicate limited exchange between suspended & sinking POM • “Suspended” (pumps): freshest; bacterial degradation with depth and progression of the season • Slowly-sinking (SV traps): bacterially-reworked material • Fastest-sinking (SV traps): biominerals & fecal pellets • Summer: more similar composition indicates more exchange between suspended & sinking POM • “Suspended” (pumps): freshest; bacterial degradation with depth • Slowly-sinking (SV traps): fresh material, BCaCO3 • Fastest-sinking (SV traps): BSi, fecal pellets, bacterially-reworked material

  15. Future Work • Examine 2005 data • SV traps at more depths (200m, 400m, & 800m) • Incorporate lipids & POC/234Th • Use data to model extent of exchange between particles of different settling velocities

  16. Acknowledgements • Jenni Szlosek & Zhanfei Liu • Michael Peterson, Robert Armstrong, Jianhong Xue, Juan-Carlos Miguel, Scott Fowler, Madeleine Goutz, Christian Tambourini, and all other MedFlux collaborators • NSF Chemical Oceanography Program

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