C age of bulk organic carbon in surface marine sediments

Particulate organic carbon transport between and within the terrestrial and marine environment Suggested Reading Lateral transport of POC Ohkouchi et al 22 Science 298 1224-1227. Mollenhauer & Eglinton 27 L&O 52 558-576. POC transfer from land to the oceans Drenzek et al 27 Mar. Chem. 13 146-162. Fossil OC cycling Drenzek et al 27 Mar. Chem. 13 146-162. Petsch et al. 21 Science 292 1127-1131. 14 C age of bulk organic carbon in surface marine sediments 14 C age (yr) 5 1 15 1 2 Water Depth (m) 3 4 5 river-dominated shelf abyssal anoxic shelf basin OMZ open shelf continental slope 6 7 1

Old carbon in the modern marine environment Possible origin(s) of non-zero 14 C ages for OC carbon in marine surface sediments: 1. Delivery of pre-aged terrestrial OC of vascular plant origin 2. Relict OC ( kerogen ) inputs from erosion of sedimentary rocks 3. Sediment redistribution processes - Bioturbation - Lateral advection 4. Black Carbon [NEXT LECTURE] A Brief Overview of the Global Organic Carbon Cycle ATMOSPHERIC CO 2 (75) SEDIMENTARY ROCKS (KEROGEN) (15,,) LAND PLANTS (57) terrestrial primary production physical weathering humification river or eolian transport marine primary production uplift SOILS (1,6) OCEAN BIOTA (3) POC (2) OC burial DOC (68) (units=1 15 gc) Modified after Hedges (1992) Sizes of boxes are not to scale burial MODERN OCEAN SEDIMENTS (1) 2

Selected observations from molecular 14 C studies of sedimentary organic matter Take home messages: Lateral transport of [particulate] organic matter is widespread in the ocean, complicating interpretation of sedimentary records, and models of carbon export and burial. Not all molecules are created equal in terms of their propensity to move around in the environment. Timescales of export of terrestrial organic matter vary significantly as a consequence of factors that we only poorly understand. The Global Organic Carbon Cycle ATMOSPHERIC CO 2 (75) SEDIMENTARY ROCKS (KEROGEN) (15,,) LAND PLANTS (57) terrestrial primary production physical weathering humification river or eolian transport marine primary production uplift SOILS (1,6) OCEAN BIOTA (3) POC (2) OC burial DOC (68) (units=1 15 gc) Modified after Hedges (1992) Sizes of boxes are not to scale burial MODERN OCEAN SEDIMENTS (1) 3

Molecular Sedimentology Using coupled molecular and microfossil 14 C measurements to study pre- and post-depositional phenomena Premise: Marine algal biomarker compounds (e.g., alkenones, sterols) and planktonic forams both encode surface ocean-derived signatures (incl. 14 C content of DIC). Age discrepancies must therefore indicate different subsequent fates. Marine organic matter is predominantly associated with the fine fraction of sediments prone to resuspension and redistribution. Foraminiferal tests are coarse, sand-sized particles less susceptible to redistribution by bottom currents. Approach: Use 14 C relationships between planktonic foraminifera, algal biomarkers (e.g., alkenones), and bulk OC isolated from the same sediment intervals as a tool to examine diagenetic & sedimentological processes (lateral transport, bioturbation). C 37 alkenone E. Huxleyi The Bermuda Rise Atlantic Ocean Located northeast of Bermuda. A deep ocean (~ 45m water depth) sediment drift. Unusually high sediment accumulation rates. Bermuda Island Subject of numerous paleoceanographic studies. Sediment box core studied using molecular carbon-14 methods. 4

Sedimentological Controls on Geochemical Records from the Bermuda Rise Age difference (vs planktonic forams) %CaCO3 1 2 3 U K ' 37 alkenones.6.8 5 TOC 5 FFIC 5 5 Age (Calendar years) 1 15 2 Ohkouchi et al. 22 Nova Scotia Cape Cod Bermuda 5

Satellite image of E. huxleyi bloom off Newfoundland in the western Atlantic on 21st July, 1999. This way to Cape Cod P.E.I. Newfoundland Nova Scotia Bermuda is ~1 km away Science goes in circles! HEBBLE Study area 6

Lateral transport of organic matter to the Bermuda Rise? Namibian margin (Benguela Upwelling region) -2 cm alkenones and bulk OC modern age 2-12 cm (pre-bomb) alkenones: 118 yrs ~ Reservoir age Namibia 1-1 cm alkenones 25 yr bulk OC 227 yr foraminifera 25 yr -5-15 -25-35 -45 Elevation (m) -55 Data from Mollenhauer et al., 23 7

14 C ages of Namibian margin sedimentary components (core 22666-5) 2 4 6 Total organic carbon Total organic carbon Depth (cm) 8 1 Alkenones Alkenones 12 14 Plantonic forams ( G. bulloides) 16 5 1 15 1 2 3 4 5 14 C age (yr) 14 C age difference vs forams (yr) Mollenhauer et al., 23 Accumulation maximum (depocenter) on upper continental slope 8 9 1 11 12 13 14 15 16 17-19 a) 1 N S -2-21 -22 Walvis Bay -23-24 -25-26 Lüderitz -27-28 -29-3 1 9 8 7 6 5 4 3 2 1 TOC (%) Water Depth [m] (Vp=15 m/s) 12 14 16 Distance [km] 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 16 17 18 19 b) erosion? increased accumulation 2 m Sites of increased accumulation in protected locations (depocenters): Implication of current controlled sedimentation Seismic data processing: André Janke Mollenhauer et al., 22 8

California Borderland Basins California Borderland Basins - Anoxic laminated sediments - High sedimentation rates Sediment and organic matter deposition in the Santa Monica Basin Terrestrial sediment Present Day ~15km shelf flank This Study: 3 sites from each basin, 2 from flanks, 1 from anoxic depocenter Analysis of core-top and one prebomb (pre-195) sediment horizon Radiocarbon dates for TOC, foraminfera, alkenones and fatty acids (C 16 C 28 ) Particle resuspension and lateral transport Sediment focusing Organic matter export from surface ocean productivity Low oxygen/anoxic bottom waters depocenter Sediment focusing flank Mollenhauer & Eglinton, in press. 9

NW flank MC49 organic carbon (wt. %) 1 2 3 4 Santa Monica Basin Depocenter MC5 organic carbon (wt. %) 1 2 3 4 5 6 Alkenones systematically 14 C depleted relative to planktic forams: - Advective supply of pre-aged alkenones year of deposition 2 19 18 17 16 15 14 13 12 Radiocarbon dated planktic forams alkenones bulk OC.7.8.9 1 1.1 Radiocarbon content (fmc) year of deposition 2 19 18 17 16 15 14 13.7.8.9 1 1.1 Radiocarbon content (fmc) Alkenone-foram 14 C offsets smaller in depocenter than flank sediments: - Superior preservation of labile, autochthonous carbon under anoxic conditions? Flank (oxic) Depocenter (anoxic) Allochthonous (advected) 29-57% (alkenones) 21-3% (alkenones) Alkenone-planktonic foram 14 C age relationships Alkenones older than forams Alkenones younger than forams Age difference ( 14 C years) 8 6 4 2-2 -4 Sample Bermuda Rise Namibian Slope Chilean Margin NW African Slope Santa Barbara Basin Namibian Shelf Scotian Shelf (Emerald Basin) New England Shelf (Mud Patch) Gulf of Mexico Oman Margin Indian Ocean Gardar/Bjorn Drift Argentine Basin S. China Sea 1

Estimates of advective alkenone contributions Assumptions: Δ 14 C of indigenous alkenones = Δ 14 C of forams Δ 14 C of advected alkenones = -1 permil (infinite 14 C age) Advected alkenone contribution (%) 6 5 4 3 2 1 Bermuda Rise Benguela Scotian Margin New England margin Gulf of Mexico Arabian Sea Santa Barbara Basin Indian Ocean NE Pacific Ocean ( (Stn M)) -1 Eglinton et al. unpublished Comparison of alkenone and TOC 14 C ages in surficial (< 3 cm) marine sediments 1 9 8 Alkenone 14 C age (years BP) 7 6 5 4 3 2 1 1:1 line 1 2 3 4 5 6 7 8 9 1 TOC 14 C age (years BP) 11

Advection of POC in the Panama Basin Druffel et al., 1998 Catching lateral particle transport in the act Line W 12

Line W physical oceanographic and biogeochemical flux studies Sediment trap moorings Sinking particle flux & Δ 14 C (3 m Station) Fall bloom Spring bloom Mass flux (mg m -2 d -1 ) 4 3 2 1 5 Δ 14 C ( ) 968 m -5 1976 m 2938 m 6/1 7/1 8/1 9/1 1/1 11/1 12/1 1/1 2/1 3/1 4/1 5/1 Date 13

Alkenones in Sinking particles (3 m Station) Fall bloom Spring bloom Mass flux (mg m -2 d -1 ) 4 3 2 1 Alkenone conc n (nc mg -1 ) Alkenone T ( o C) 1 5 3 25 2 15 1 1976 m 2938 m 5 6/1 7/1 8/1 9/1 1/1 11/1 12/1 1/1 2/1 3/1 4/1 5/1 Date Dynamics of Carbon Export in the Arctic Ocean BGOS mooring 24-25 - Virtually land-locked ocean, deep basin waters (esp. Canada Basin) partially isolated. - Has the largest percentage of shelf area of all the World s oceans. - Biogeochemical processes strongly influenced by sea-ice coverage/dynamics. 14

Time-series measurements at BGOS mooring-a (383m) Ice cover (%) Current speed (cm/s) Flux (mgm -2 d -1 ) Δ 14 C ( ) 1 8 6 4 2 4 2-2 -4 4 3 2 1-12 -16-2 -24-28 a) b) c) d) OM CaCO3 Opal Lithogenic -24-25 -26 9/1 1/111/112/1 1/1 2/1 3/1 4/1 5/1 6/1 7/1 8/1 9/1 24 Date 25 δ 13 C ( ) Advective particulate carbon supply to the Canada Basin 15

Additional evidence for advective OC supply to the sea floor (i) Increased material fluxes in deep, relative to shallow, sediment traps deployed near continental slopes (Honjo et al., 1982; Biscaye et al., 1988; Thomsen & van Weering, 1998). (ii) High suspended particle concentrations near the seafloor (bottom nepheloid layer; McCave, 1983; Gardner & Sullivan, 1981) or associated with the detachment of intermediate nepheloid layers from the upper slope (INLs; Biscaye et al., 1988; Pickart, 2). (iii) Carbon and oxygen imbalances in the deep ocean (Jahnke et al., 1996). (iv) Old 14 C ages of OC on suspended particles in slope waters (Bauer et al., 21). (v) 14 C age of particles on slope waters intercepted by sediment traps (Anderson et al., 1994; Hwang et al., 24). (vi) The isotopic and molecular composition of deep sea sediments (Freudenthal et al., 21; Benthien & Müller, 2). Organic matter cycling on continental margins: Importance of lateral transport Terrigenous input 16

Organic matter cycling on continental margins: Importance of lateral transport Terrigenous input The Global Organic Carbon Cycle ATMOSPHERIC CO 2 (75) SEDIMENTARY ROCKS (KEROGEN) (15,,) LAND PLANTS (57) terrestrial primary production physical weathering humification river or eolian transport marine primary production uplift SOILS (1,6) OCEAN BIOTA (3) POC (2) OC burial DOC (68) sediment redistribution (units=1 15 gc) Modified after Hedges (1992) Sizes of boxes are not to scale burial MODERN OCEAN SEDIMENTS (1) 17

The Global Organic Carbon Cycle ATMOSPHERIC CO 2 (75) SEDIMENTARY ROCKS (KEROGEN) (15,,) LAND PLANTS (57) terrestrial primary production physical weathering humification river or eolian transport marine primary production uplift SOILS (1,6) OCEAN BIOTA (3) POC (2) OC burial DOC (68) sediment redistribution (units=1 15 gc) Modified after Hedges (1992) Sizes of boxes are not to scale burial MODERN OCEAN SEDIMENTS (1) Overarching Questions What is the age of terrestrial (vascular plant-derived) carbon discharged by rivers to the ocean? Where in the drainage basin do terrestrial organic carbon signatures emanate from? How do terrestrial organic carbon residence times vary with drainage basin properties? Relevance Timescales of change in terrestrial vs oceanic carbon cycle in response to climate variations/anthropogenic perturbations. Understand pathways of terrestrial organic matter transport. Interpretation of marine and terrestrial proxy records from marine sediments. 18

Δt plant wax lipids Bulk vs molecular-level 14 C analysis of riverine organic matter 5 C24 n-acid Ob-1 Ob-2 Mackenzie C26 n-acid C28 n-acid C3 n-acid 1 Ob-1 bulk 15 2 Riverine 1 & 2 prodn Ob-2 bulk 14 C age (years b.p.) 25 3 35 4 6 8 1 Fossil (kerogen) OC Mackenzie bulk Dickens et al. in prep. Drenzek et al 27 12 C24 n-acid C26 n-acid C28 n-acid C3 n-acid 19

Molecular multi-isotopic studies of riverine organic matter Mackenzie Cowichan (Saanich) Columbia Eel Pettaquamscutt Danube Ob Mississippi Unare (Cariaco) Beni Congo Waiapu Beaufort Sea - River-dominated (Mackenzie) - Old organic carbon inputs Molecular Multi-Isotopic Studies of Marine Sediments Box Core Surface Grab Particulate Washington Margin - River-dominated (Columbia R) 2

Radiocarbon ages of vascular plant wax biomarkers in Washington Margin and Beaufort Sea surface sediments Carbon number 21 TOC 22 23 24 25 26 27 28 29 3 31 32 WM St2 TOC WM St2 FA 5 WM St2 HC Washington Margin (St 2, 83 m) BS St5 TOC BS St5 FA 1 BS St5 HC 14 C age (yr) 15 4 6 8 1 12 Beaufort Sea (St 5, 25 m) Drenzek et al., in press; Eglinton, unpublished results 1 Drainage Basin Area 1 Sediment Load -1-1 Δ 14 C (permil) -2-3 -4 Δ 14 C (permil) -2-3 -4-5 -6 ave acid D14C 1 1 1 Drainage Basin Area (km 2 ) -5-6 ave acid D14C 1 1 Sediment Load (Mt/yr) 1 Sediment Yield ave acid D14C Still to evaluate: Δ 14 C (permil) -1-2 -3-4 -5 - Discharge -Elevation - Vegetation type - Bedrock type -6 1 1 1 1 Sediment yield (t/km 2 /yr) 21

Δ 14 C of long-chain plant wax lipids vs river latitude ave acid D14C ave OH D14C ave HC D14C Δ 14 C (permil) -2-4 Increasing 14 C age at higher latitudes -6 2 4 6 Latitude N/S δ 13 C n-c 24 alcohol ( VPDB) Δ 14 C age (n-c 24 alcohol forams) Relationship between climate, vegetation & continental residence times in central W. Africa -35-34 -33-32 -31-3 3 25 2 15 1 5 C3-dominated vegetation (rainforest) Contains bomb 14C aridification of drainage basin Increasing residence time n-c24 alcohol -13-135 -14-145 -15-155 -16 δd n-c 24 alcohol ( VSMOW) 1 2 3 4 5 6 7 8 9 1 Calendar age Schefuss et al., unpublished 22

Temporal relationship between wax biosynthesis and aeolian transport - rapid but not necessarily young? Fractions Carbon isotopic composition of dustfall sample off NW Africa Abundance δ 13 C ( ) Δ 14 C ( ) 14 C age (yr BP) Total Organic Carbon 1.2 % -18.93-149.6 126 ± 4 Black Carbon.24 % -15.13-231.7 27 ± 35 Plant wax alcohols 12 μg/gdw -27.9-8.8 649 ± 143 Eglinton et al., 23 Isotopic characterization of size-fractionated sediments from the Washington Margin Washington Margin (Columbia R) Upper slope Outer shelf 23

Radiocarbon ages of individual fatty acids in size-fractionated sediments WM3 WM4 Terrestrial (long-chain) fatty acids older in Outer shelf Upper slope slope than shelf surface sediments - Aging during lateral transport? Terrestrial fatty acid age increases with increasing grain-size -More rapid nepheloid layer transport of fine particles? Aging during transport? Can 14 C measurements on vascular plant markers yield information on timescales of across-margin transport of sedimentary particles? Grain size Uchida et al., unpublished results The Global Organic Carbon Cycle ATMOSPHERIC CO 2 (75) SEDIMENTARY ROCKS (KEROGEN) (15,,) LAND PLANTS (57) terrestrial primary production physical weathering humification river or eolian transport marine primary production uplift SOILS (1,6) OCEAN BIOTA (3) POC (2) OC burial DOC (68) sediment redistribution (units=1 15 gc) Modified after Hedges (1992) Sizes of boxes are not to scale burial MODERN OCEAN SEDIMENTS (1) 24

The Global Organic Carbon Cycle ATMOSPHERIC CO 2 (75) SEDIMENTARY ROCKS (KEROGEN) (15,,) LAND PLANTS (57) terrestrial primary production physical weathering humification river or eolian transport marine primary production SOILS (1,6) OCEAN BIOTA (3) uplift POC (2) OC burial DOC (68) sediment redistribution (units=1 15 gc) Modified after Hedges (1992) Sizes of boxes are not to scale burial MODERN OCEAN SEDIMENTS (1) 14 C ages of fatty acids & alkanes in Beaufort Sea sediments 5 Stn5 Stn35 Stn144 14 C age (yr BP) 1 15 2 25 n-fatty acids = open symbols n-alkanes = closed symbols Fossil OC component 15 2 25 3 Carbon number Drenzek et al., 27 25

Return of fossil carbon to the biosphere: 14 C-dead living biomass! Evidence for microbial assimilation of kerogen during shale weathering PLFA Δ 14 C F ancient carbon δ 13 C C 16: -711.744-25.5 25 μm C 18: -773.82-26.2 C 18:1 +C 18:2-882.91-26.5 cyc-c 17: +cyc-c 19: -922.937-26.9 Kerogen -99-29.5 Petsch et al, 21, Science, 292, 1127-1128 26

14 C age variability in Bermuda Rise surface (-3 cm) sediment Δ 14 C (permil) -2-4 -6-8 -1 G. ruber G. inflata Tracer of DIC 14 C in overlying surface waters planktonic forams Labile algal biomarkers total (minor organic advected carbon component?) 1 alkenones fatty acids 2 hydrocarbons 3 Refractory algal Pre-aged biomarkers refractory (large plant advected waxes component) 4 (advected + eolian component)? 5 TOC (-1cm) TOC (1-2cm) Alkenones (-1cm) Alkenones (1-2cm) C16 fatty acid C18 fatty acid C24 fatty acid C26 fatty acid C28 fatty acid Bulk OC = advected marine OM? C21+C23+C25 alkanes C22+C24+C26 alkanes C27 alkane C29+C31 alkanes C28+C3+C32 alkanes UCM 1 15 2 3 14C age (yr BP) Petrogenic hydrocarbons (fossil inputs) Ohkouchi et al., submitted Calculation of % terrestrial, marine and fossil OC Dual isotopic mass balance approach: Δ 14 C TOC = f marine * Δ marine + f terrestrial * Δ terrestrial + f fossil * Δ fossil δ 13 C TOC = f marine * δ marine + f terrestrial * δ terrestrial + f f ossil * δ fossil f marine + f terrestrial + f fossil = 1 Variable Measurement/assumption: Δ 14 C TOC measure directly (AMS) δ 13 C TOC measure directly (irms) Δ 14 C marine measure phytoplankton sterol (PCGC/AMS) Δ 14 C terrestrial measure lignin phenol/plant wax (PCGC/AMS) Δ 14 C fossil stipulate as 1 δ 13 C marine measure phytoplankton sterol (irm-gc-ms) - assume offset between biomarker and bulk OC δ 13 C terrestrial measure lignin phenol/plant wax (irm-gc-ms) - assume offset between biomarker and bulk OC δ 13 C fossil assume value based on regional stratigraphy - (or measure biomarker selected based on Δ 14 C) 27

Dual Isotope Mass Balance % 1 9 8 7 6 5 4 3 2 1-19 -21.7 Arabian Sea -251-2.7 Benguela Upwellin -16-23. Santa Monica Basin -18-24.2 Black Sea Unit I Black Sea Unit II marine vascular plant relict -468-25.36-6 -194-22.68-25.29 Bermuda Rise Washington Margin St2-136 -25.24 Washington Margin St1-57 -21.7 Gulf Of Mexico -876-3 -395-555 -712-28.26-24.4-27.42-26.35-25.65 Beaufort Sea Ross Sea (Chinstra Ross Sea (Gentoo) Ross Sea (Emperor) Ross Sea (Fairy) Δ 14 C TOC δ 13 C TOC Ross Sea (Fairy) Ross Sea (Emperor) Ross Sea (Gentoo) Ross Sea (Chinstrap) Beaufort Sea Gulf Of Mexico Washington Margin St1 Washington Margin St2 Bermuda Rise Black Sea Unit II Black Sea Unit I Santa Monica Basin Benguela Upwelling Arabian Sea 28