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Organic Composition of Particulate Organic Matter: Implications for the Exchange of Material Between Suspended and Sinking Particles Lynn Abramson1*,

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Presentation on theme: "Organic Composition of Particulate Organic Matter: Implications for the Exchange of Material Between Suspended and Sinking Particles Lynn Abramson1*,"— Presentation transcript:

1 Organic Composition of Particulate 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

2 Organic Matter Composition
POM composition reflects: Source Alteration Exchange among pools Continual aggregation/ disaggregation, or remain intact as they sink? The rate of remineralization (R) vs. exchange (E) should determine how the compositions of fast- and slowly-sinking particles relate. If there is little or no exchange between fast- and slowly-sinking particle pools, the difference in DI and POC/Th between the two pools should increase with depth. Implications for amount and composition of OM exported to depth

3 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) Slowly-sinking Fast-sinking Extent of Degradation ? Depth Surface 200m 800m 1500m

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 Particle Types “Suspended” Particles: Pumps “Sinking” Particles: Traps
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 Trap

6 Overview of Conditions
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 Pumps Maximum fluxes in March, 2003

7 Composition with Depth: Early Spring 2003 (Mar. 4 – 11)
Pigment Composition (%) Depth (m) diatom deg. FP Amino Acid Composition (%) SiO2 CaCO3 deg. Sinking particles (TR) more degraded than suspended Suspended particles look degraded with depth- due to their own degradation, or exchange with sinking POM? More diatoms in traps SPRING= Pumps: May 7-12; Traps: Apr. 30-May 6 SUMMER= Pumps: Jun. 30; Traps: Jun *TR= time series traps; rest are pumps

8 Composition with Depth: Late Spring 2003 (Apr. 30 – May 12)
Pigment Composition (%) Depth (m) diatom deg. FP Amino Acid Composition (%) SiO2 CaCO3 Sinking particles (TR) more degraded than suspended Suspended particles look degraded with depth- due to their own degradation, or exchange with sinking POM? More diatoms in traps SPRING= Pumps: May 7-12; Traps: Apr. 30-May 6 SUMMER= Pumps: Jun. 30; Traps: Jun *TR= time series traps; rest are pumps

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

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

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

12 Composition with Settling Velocity
Traps Pumps direction of alteration 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) PC 1 (32.9%) PC 2 (17%) Degradation in the order summer traps > spring traps > Jun pumps (though a bit mixed) > May pumps > March pumps Suspended particles fresher Sinking particles contain more degraded OR diatom-rich material (esp. spring)- rich in ZP and bacterial decomp. products *variable loadings scaled up 10x to fit axes

13 Composition with Settling Velocity
PC 1 (36.7%) PC 2 (26%) Spring (Mar.-May) 200m SV Trap settling velocity Bacterial BSi, BCaCO3, Fresh, & Fecal Pellets PC 1 (41.6%) PC 2 (20.5%) Summer (May-Jun.) 200m SV Trap Bacterial, Fecal Pellets, & BSi Fresh & BCaCO3 *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 Incorporate lipids & POC/234Th
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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