Terrestrial Plants 900 GT C Terrestrial Primary Production 75 GT C/yr. River flux 0.5 GT C/yr. Carbonates 60,000,000 GT C

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1 Most of the organic carbon on earth is stored in long term deposits (shales, coals, sedimentary rocks) that represent a leak from the contemporary C cycle Terrestrial Plants 900 GT C Terrestrial Primary Production 75 GT C/yr Atmosphere 750 GT (CO 2 ) Soil 2000 GT C River flux 0.5 GT C/yr Marine Primary Production GT C/yr Carbonates 60,000,000 GT C Kerogen 20,000,000 GT C POC 15 GT C Burial Biomass 2 GT GT C/yr DOC 700 GT C 150 GT C The composition of organic matter in marine sediments and the mechanisms of carbon preservation What determines how much carbon makes it to the sea floor, How much is mineralized, and how much is buried? 1) Selective preservation: Some compounds are intrinsically more labile than others, and will be preserved in sediments. 2) Physical protection/encapsulation: Organic matter can be locked up In clay minerals, cysts, etc and preserved. 3) Geopolymer model: Simple biomolecules (sugars, amino acids, lipids) recombine through unknown reactions to form complex substances that are not easy to degrade. These are not mutually exclusive.!

2 What factors drive the export of carbon (the biological pump) to marine sediments Geographic correlation between carbon flux and wt% C in

3 Selective preservation of OM during early diagenesis: Δ C/N and relative amounts of organic matter show some selective preservation must occur C:N = 6.6 C:N = 9.0 From Lee et al. (2004) Ambio 33, How well do we know the composition of marine algae? CH 3 CH(N)COOH proteins I, II, III, VII C(H 2 O) carbohydrates III CH 3 (CH 2 ) n COOH lipids I, V, VII Hedges et al. (2002) Marine Chemistry v 78, pp 47-63

4 13 CNMR of phytoplankton, shallow and deep sediment trap material (Equatorial Pacific) Surface protein carbo lipid 1000 m 3500 m 13 CNMR of phytoplankton, shallow and deep sediment trap material (Arabian Sea)

5 From the small changes in the 13 CNMR spectra of sinking POM, Hedges et al. infer that C degradation does not select for different groups of organic carbon. Intrinsic lability is not a major factor in C preservation. Instead they argue that preservation occurs via physical protection. Reconciling selective and nonselective preservation the effects of mineral ballast on C flux Organic matter on sinking particles is made up of protected and nonprotected forms. The nonprotected OM is lost in the upper water column, protected is not, and its flux will vary with the amount of mineral flux.

6 Reconciling selective and nonselective preservation the effects of mineral ballast on C flux As more of the material is ballasted, the F org /EP increases F org = fraction organic carbon & EP = export production Francois et al. (2002) GBC 16 doi:10,1029/2001gb001722, 2002: Testing the mineral protection hypothesis: Do mineral bound amino acids make up a large fraction of the sinking POM at at depth in the ocean?.not really, at least not in the southern ocean.

7 How well do we know the composition of marine algae? Molecular analyses of phytoplankton cannot account for the NMR distributions of functional groups Do protein/carbohydrates/lipids account for most of the C&N in algae, and are the functional group assignments correct? If C/N increases with depth from 7-> 8 or 9.7, Then why isn t this reflected in the 13 CNMR? From the small changes in the 13 CNMR spectra of sinking POM, Hedges et al. infer that C degradation does not select for different groups of organic carbon. Intirnsic lability is not a major factor in C preservation. Instead they argue that preservation occurs via physical protection.

8 NMR spectra of fresh algae. 15 N and 13 CNMR show a large fraction of the material is protein, (amide, CON, CHO & CH x ) Knicker et al Org Geo 24, N-NMR 13 CNMR O = C-C-N amide O - C-C-NH = amine Physical entrapment into resistant geopolymers 13 CNMR of mixed algae From laboratory culture The same culture material After 2 months of degradation Knicker et al Org Geo 24,

9 15 N- and 13 CNMR study of algal degradation Knicker et al Org Geo 24, Fresh algae Algal compost (60 d) Algaenan (nonextractable POM) 15 N and 13 CNMR of an algal 4000 yr old sapropel from Mangrove Lake, Bermuda Knicker et al Org Geo 24, Note presence of Amide (?) 15 N 13 C Knicker reasons that amide comes from protein, which should be labile. Preservation suggests some form of physical protection

10 Does a biomolecule have to change its Composition to affect its lability? Keil and Kirchman Another way to think about selective preservation. What are the isotopic consequences of degradation? Acid insoluble Lipid Carbohydrate TH amino acids J. Hwang & E.R.M. Druffel (2003) Science,

11 Another way to think about selective preservation. What are the isotopic consequences of degradation? Acid insoluble Lipid Carbohydrate TH amino acids As organic matter ages (14C) the amount of acid insoluble C increases.. J. Hwang & E.R.M. Druffel (2003) Science, And the C isotope ratios of the acid insoluble fraction looks a lot like lipids. DIC Acid insoluble Lipid Carbohydrate TH amino acids J. Hwang & E.R.M. Druffel (2003) Science,

12 Summary Greater than 98% of the carbon that is produced in surface water is never buried in sediments. It is biologically recycled in the water column. The ocean carbon cycle is very efficient. Most of our knowledge of particle flux and early diagenesis comes from sediment traps, which selects for a very certain type of sinking particle (large & heavy). On the preservation side, three mechanisms have been evoked to account for preservation- the presence of intrinsically recalcitrant organic matter, mineral protection, and geopolymerization. Good evidence exists to support selective preservation, evidence for mineral protection and geopolymerization is much weaker.