Particulate organic carbon transport between and within the terrestrial
and marine environment
Suggested Reading
•
Lateral transport of POC
– Ohkouchi et al 2002 Science 298 1224-1227.
– Mollenhauer & Eglinton 2007 L&O 52 558-576.
•
POC transfer from land to the oceans
– Drenzek et al 2007 Mar. Chem. 103 146-162.
•
Fossil OC cycling
– Drenzek et al 2007 Mar. Chem. 103 146-162.
– Petsch et al. 2001 Science 292 1127-1131.
age of bulk organic carbon in surface marine sediments
14
C age (yr)
0
5000
10000
15000
0
1000
2000
Water Depth (m)
14C
3000
4000
river-dominated shelf
abyssal
anoxic shelf basin
OMZ
open shelf
continental slope
5000
6000
7000
1
Old carbon in the modern marine environment
Possible origin(s) of non-zero 14C 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 CO2
(750)
terrestrial primary
production
SEDIMENTARY
ROCKS
(KEROGEN)
(15,000,000)
p
we hysic
ath al
eri
ng
LAND PLANTS
(570)
humification
SOILS
(1,600)
uplift
marine
primary
production
riv
er
tra or eo
ns
po lian
rt
OCEAN BIOTA (3)
POC (20)
DOC (680)
OC burial
burial
MODERN OCEAN
SEDIMENTS (100)
(units=1015gC)
Modified after Hedges (1992)
Sizes of boxes are not to scale
2
Selected observations from molecular 14C 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 CO2
(750)
terrestrial primary
production
SEDIMENTARY
ROCKS
(KEROGEN)
(15,000,000)
p
we hysic
ath al
eri
ng
LAND PLANTS
(570)
humification
SOILS
(1,600)
uplift
marine
primary
production
riv
er
tra or eo
ns
po lian
rt
OCEAN BIOTA (3)
POC (20)
DOC (680)
OC burial
burial
MODERN OCEAN
SEDIMENTS (100)
(units=1015gC)
Modified after Hedges (1992)
Sizes of boxes are not to scale
3
“Molecular Sedimentology”
Using coupled molecular and microfossil 14C 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. 14C 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 14C 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).
C37 “alkenone”
E. Huxleyi
The Bermuda Rise
Atlantic
Ocean
Located northeast of Bermuda.
A deep ocean (~ 4500m 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
10
20
30
K
U37'
0.6
0.8
alkenones
0
5000
TOC
0
5000
FFIC
0
5000
0
Age (Calendar years)
500
1000
1500
2000
Ohkouchi et al. 2002
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.
ew
N
fo
Nova Scotia
d
un
nd
la
Bermuda is
~1000 km away
Science goes in circles!
HEBBLE
Study area
6
Lateral transport of organic matter to the Bermuda Rise
?
Namibian margin (Benguela Upwelling region)
2-12 cm (pre-bomb)
alkenones: 1180 yrs
~ Reservoir age
0-2 cm
alkenones and bulk OC
modern age
Nam
ibia
1000
0
0-1 cm
alkenones 2500 yr
bulk OC 2270 yr
foraminifera 25 yr
-1500
-2500
-3500
Elevation (m)
-500
-4500
-5500
Data from Mollenhauer et al., 2003
7
14C
ages of Namibian margin sedimentary components (core 226660-5)
0
20
40
Total organic
carbon
Depth (cm)
60
80
Total organic
carbon
Alkenones
Alkenones
100
120
Plantonic forams
( G. bulloides)
140
160
0
5000
10000
15000
0
1000
14
14
C age (yr)
2000
3000
4000
5000
C age difference vs forams (yr)
Mollenhauer et al., 2003
Accumulation maximum (depocenter) on upper continental slope
a)
9
10 11 12 13 14 15 16 17
-19
1000
-20
-21
9
-23
8
7
6
-25
5
-26
4
3
-27
2
-28
1
-29
0
TOC (%)
-24
Lüderitz
10
-22
Walvis Bay
Water Depth [m] (Vp=1500 m/s)
8
S
N
1200
erosion?
increased
accumulation
1400
1600
Distance [km] 10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
b)
-30
20 m
Sites of increased
accumulation in protected
locations (depocenters):
Implication of current
controlled sedimentation
Seismic data processing: André Janke
Mollenhauer et al., 2002
8
California Borderland Basins
California Borderland Basins
- Anoxic laminated sediments
- High sedimentation rates
Sediment and organic matter deposition in the Santa Monica Basin
Te
rre
str
ial
se
dim
en
t
Present Day
~15km
Particle
resuspension and Organic matter export from
lateral transport surface ocean productivity
shelf
flank
flank
Low oxygen/anoxic
Sediment
bottom waters
focusing
This Study:
3 sites from each basin, 2 from flanks,
1 from anoxic depocenter
Analysis of core-top and one “prebomb“ (pre-1950) sediment horizon
Radiocarbon dates for TOC,
foraminfera, alkenones and fatty
acids (C16 – C28)
Sediment
focusing
depocenter
Mollenhauer & Eglinton, in press.
9
Santa Monica Basin
NW flank
Depocenter
MC50
MC49
organic carbon (wt. %)
0
1
2
3
organic carbon (wt. %)
4
1
2000
year of deposition
year of deposition
3
4
5
6
- Advective supply of pre-aged
alkenones
Alkenone-foram 14C offsets smaller
in depocenter than flank sediments:
1900
1800
1700
1600
1500
1300
2
2000
1900
1400
Alkenones systematically 14C
depleted relative to planktic forams:
Radiocarbon dated
planktic forams
alkenones
bulk OC
1200
- Superior preservation of labile,
autochthonous carbon under anoxic
conditions?
1800
1700
1600
Allochthonous
(advected)
1500
1400
1300
0.7
0.8
0.9
1
1.1
Radiocarbon content (fMC)
0.7
0.8
0.9
1
1.1
Radiocarbon content (fMC)
Flank (oxic)
29-57%
(alkenones)
Depocenter
(anoxic)
21-30%
(alkenones)
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
8000
6000
14
Age difference ( C years)
Alkenones younger than forams
Alkenones older than forams
Alkenone-planktonic foram 14C age relationships
4000
2000
0
-2000
-4000
Sample
10
Estimates of advective alkenone contributions
Assumptions:
Δ14C of indigenous alkenones = Δ14C of forams
Δ14C of advected alkenones = -1000 permil (infinite 14C age)
Advected alkenone contribution (%)
60
Bermuda Rise
Benguela
Scotian Margin
New England margin
Gulf of Mexico
Arabian Sea
Santa Barbara Basin
Indian Ocean
NE Pacific Ocean ( (Stn M))
50
40
30
20
10
0
-10
Eglinton et al. unpublished
Comparison of alkenone and TOC 14C ages
in surficial (< 3 cm) marine sediments
10000
9000
14
Alkenone C age (years BP)
8000
7000
6000
5000
1:1
e
lin
4000
3000
2000
1000
0
0
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
14
TOC C age (years BP)
11
Advection of POC in the Panama Basin
Druffel et al., 1998
Catching lateral particle transport in the act
Lin
eW
12
Line W physical oceanographic and biogeochemical flux studies
Sediment trap moorings
Sinking particle flux & Δ14C (3000 m Station)
Fall bloom
Spring bloom
-2 -1
Mass flux (mg m d )
400
300
200
100
0
0
14
Δ C (‰)
50
968 m
1976 m
2938 m
-50
6/1
7/1
8/1
9/1
10/1
11/1
12/1
1/1
2/1
3/1
4/1
5/1
Date
13
Alkenones in Sinking particles (3000 m Station)
Fall bloom
Spring bloom
300
200
100
Alkenone conc
-1
(nC mg )
n
Mass flux
-2 -1
(mg m d )
400
0
10
5
0
30
Alkenone T
o
( C)
25
1976 m
2938 m
20
15
10
5
6/1
7/1
8/1
9/1
10/1
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
2004-2005
- 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
4
b)
2
0
-2
-4
40
c)
OM
CaCO3
Opal
Lithogenic
30
20
10
d)
-24
-120
-160
-25
-200
13
0
δ C (‰)
14
Δ C (‰)
Time-series
measurements at
BGOS mooring-A
(3083m)
-2 -1
Flux (mgm d ) Current speed (cm/s) Ice cover (%)
a)
100
80
60
40
20
0
-240
-26
-280
9/1 10/111/112/1 1/1 2/1 3/1 4/1 5/1 6/1 7/1 8/1 9/1
2004
Date
2005
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, 2000).
(iii) Carbon and oxygen imbalances in the deep ocean (Jahnke et al., 1996).
(iv) Old 14C ages of OC on suspended particles in slope waters (Bauer et al., 2001).
(v) 14C age of particles on slope waters intercepted by sediment traps (Anderson et al.,
1994; Hwang et al., 2004).
(vi) The isotopic and molecular composition of deep sea sediments (Freudenthal et al.,
2001; Benthien & Müller, 2000).
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 CO2
(750)
terrestrial primary
production
SEDIMENTARY
ROCKS
(KEROGEN)
(15,000,000)
p
we hysic
ath al
eri
ng
LAND PLANTS
(570)
humification
SOILS
(1,600)
uplift
marine
primary
production
riv
er
tra or eo
ns
po lian
rt
OCEAN BIOTA (3)
POC (20)
DOC (680)
OC burial
burial
sediment
redistribution
MODERN OCEAN
SEDIMENTS (100)
(units=1015gC)
Modified after Hedges (1992)
Sizes of boxes are not to scale
17
The Global Organic Carbon Cycle
ATMOSPHERIC CO2
(750)
terrestrial primary
production
SEDIMENTARY
ROCKS
(KEROGEN)
(15,000,000)
p
we hysic
ath al
eri
ng
LAND PLANTS
(570)
humification
marine
primary
production
riv
er
tra or eo
ns
po lian
rt
SOILS
(1,600)
OCEAN BIOTA (3)
uplift
POC (20)
DOC (680)
OC burial
sediment
redistribution
MODERN OCEAN
SEDIMENTS (100)
burial
(units=1015gC)
Modified after Hedges (1992)
Sizes of boxes are not to scale
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
1000
Ob-1 bulk
1500
Riverine 1° & 2° prodn
Ob-2 bulk
2000
C age (years b.p.)
ac
i
n-
Ob-1
Ob-2
Mackenzie
500
14
d
d
ac
i
C
30
0
C
28
C
24
C
26
n-
n-
ac
i
ac
i
d
d
Bulk vs molecular-level
analysis of riverine organic
matter
n-
14C
2500
3000
3500
4000
6000
8000
Fossil (kerogen) OC
10000
id
30
C
C
28
n-
n-
ac
n26
C
ac
ac
id
id
id
ac
n24
C
Dickens et al. in prep.
Drenzek et al 2007
Mackenzie bulk
12000
19
Molecular multi-isotopic studies of
riverine organic matter
Mackenzie
Cowichan (Saanich)
Columbia
Eel
Ob
Danube
Pettaquamscutt
Mississippi
Unare (Cariaco)
Congo
Beni
Waiapu
Beaufort Sea
Molecular Multi-Isotopic
- River-dominated (Mackenzie)
- Old organic carbon inputs
Studies of Marine Sediments
Box Core
Surface Grab
Particulate
Washington Margin
- River-dominated
(Columbia R)
20
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
30
31
32
0
WM St2 TOC
WM St2 FA
WM St2 HC
BS St5 TOC
BS St5 FA
BS St5 HC
500
Washington Margin (St 2, 83 m)
1500
14
C age (yr)
1000
4000
Beaufort Sea (St 5, 25 m)
6000
8000
10000
12000
Drenzek et al., in press; Eglinton, unpublished results
Drainage Basin Area
100
0
-100
Δ C (permil)
0
-100
-200
Sediment Load
-200
-300
14
-300
14
Δ C (permil)
100
-400
ave acid D14C
-500
-400
-500
ave acid D14C
-600
-600
10000
100000
1000000
10
2
100
Sediment Load (Mt/yr)
Drainage Basin Area (km )
ave acid D14C
100
Sediment Yield
0
- Discharge
- Elevation
- Vegetation type
- Bedrock type
-200
-300
14
Δ C (permil)
-100
Still to evaluate:
-400
-500
-600
10
100
1000
10000
2
Sediment yield (t/km /yr)
21
Δ14C of long-chain plant wax lipids vs river latitude
ave acid D14C
ave OH D14C
ave HC D14C
-200
In c
rea
sin
g
14
Δ C (permil)
0
14
Ca
ge
-400
at
hi g
he
r la
ti tu
de
s
-600
0
20
40
60
Relationship between climate, vegetation & continental
residence times in central W. Africa
-35
C3-dominated vegetation (rainforest)
-34
-33
-130
-32
arid
if
-31
Δ14C age
(n-C24 alcohol–forams)
-30
3000
Increa
2500
2000
1500
1000
Contains bomb 14C
500
-135
icat
ion
of d
rain
ag
-140
-145
e ba
si n
sing r
esiden
ce tim
-150
-155
e
δD n-C24 alcohol (‰ VSMOW)
δ13C n-C24 alcohol (‰ VPDB)
Latitude N/S
-160
n-C24 alcohol
0
0
1000
2000
3000
4000
5000
6000
Calendar age
7000
8000
9000
10000
Schefuss et al., unpublished
22
Temporal relationship between wax biosynthesis and aeolian transport
- rapid but not necessarily young?
Carbon isotopic composition of dustfall sample off NW Africa
Abundance
δ13C
(‰)
Δ14C
(‰)
Total Organic Carbon
1.02 %
-18.93
-149.6
1260 ± 40
Black Carbon
0.24 %
-15.13
-231.7
2070 ± 35
12 μg/gdw
-27.9
-80.8
649 ± 143
Fractions
Plant wax alcohols
14C
age
(yr BP)
Eglinton et al., 2003
Isotopic characterization of size-fractionated sediments
from the Washington Margin
Upper
slope
Outer
shelf
Washington Margin
(Columbia R)
23
Radiocarbon ages of individual fatty acids
in size-fractionated sediments
WM3
WM4
• Terrestrial (long-chain)
fatty acids
older in
slope than shelf surface sediments
- Aging during lateral transport?
Outer shelf
• Terrestrial fatty acid age increases with
increasing grain-size
-More rapid nepheloid layer transport
of fine particles?
Upper slope
Aging during transport?
• Can 14C 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 CO2
(750)
terrestrial primary
production
SEDIMENTARY
ROCKS
(KEROGEN)
(15,000,000)
p
we hysic
ath al
eri
ng
LAND PLANTS
(570)
humification
SOILS
(1,600)
uplift
marine
primary
production
riv
er
tra or eo
ns
po lian
rt
OCEAN BIOTA (3)
POC (20)
DOC (680)
OC burial
burial
sediment
redistribution
MODERN OCEAN
SEDIMENTS (100)
(units=1015gC)
Modified after Hedges (1992)
Sizes of boxes are not to scale
24
The Global Organic Carbon Cycle
ATMOSPHERIC CO2
(750)
terrestrial primary
production
SEDIMENTARY
ROCKS
(KEROGEN)
(15,000,000)
LAND PLANTS
(570)
p
we hysic
ath al
eri
ng
humification
marine
primary
production
riv
er
tra or eo
ns
po lian
rt
SOILS
(1,600)
OCEAN BIOTA (3)
uplift
POC (20)
DOC (680)
sediment
redistribution
OC burial
MODERN OCEAN
SEDIMENTS (100)
burial
(units=1015gC)
Modified after Hedges (1992)
Sizes of boxes are not to scale
14C
ages of fatty acids & alkanes in Beaufort Sea sediments
0
Stn5
Stn35
Stn144
10000
n-fatty acids = open symbols
n-alkanes = closed symbols
15000
14
C age (yr BP)
5000
20000
Fossil OC
component
25000
15
20
25
Carbon number
30
Drenzek et al., 2007
25
Return of fossil carbon to the biosphere: 14C-dead living biomass!
Evidence for microbial assimilation of kerogen during shale weathering
25 μm
PLFA
Δ14C
Fancient carbon δ13C
C16:0
-711
0.744
-25.5
C18:0
-773
0.802
-26.2
C18:1+C18:2
-882
0.901
-26.5
cyc-C17:0+cyc-C19:0
-922
0.937
-26.9
Kerogen
-990
-29.5
Petsch et al, 2001, Science, 292, 1127-1128
26
14C
age variability in Bermuda Rise surface (0-3 cm) sediment
Tracer of DIC 14C in overlying surface waters
C16 fatty acid
C18 fatty acid
Alkenones (1-2cm)
Alkenones (0-1cm)
TOC (0-1cm)
3000
10000
15000
UCM
C29+C31 alkanes
C28+C30+C32 alkanes
C27 alkane
C21+C23+C25 alkanes
Bulk OC = advected marine OM?
C22+C24+C26 alkanes
C28 fatty acid
C24 fatty acid
14
5000
C26 fatty acid
TOC (1-2cm)
G. ruber
2000
Refractory algal
Pre-aged
biomarkers
refractory
(large
plant
advected
waxes component)
4000
(advected + eolian component)?
-600
-800
component?)
1000
age (yr BP)
-400
Labile algal
planktonic forams
biomarkers total
(minor
organicadvected
carbon
alkenones
fatty acids
hydrocarbons
14C
Δ C (permil)
-200
G. inflata
0
0
-1000
20000
30000
Petrogenic hydrocarbons (fossil inputs)
Ohkouchi et al., submitted
Calculation of % terrestrial, marine and fossil OC
Dual isotopic mass balance approach:
Δ14CTOC = fmarine * Δmarine + fterrestrial * Δterrestrial + ffossil * Δfossil
δ13CTOC = fmarine * δmarine + fterrestrial * δterrestrial + ffossil * δfossil
fmarine + fterrestrial + ffossil = 1
Variable
Δ14CTOC
δ13CTOC
Δ14Cmarine
Δ14Cterrestrial
Δ14Cfossil
δ13Cmarine
δ13Cterrestrial
δ13Cfossil
Measurement/assumption:
measure directly (AMS)
measure directly (irMS)
measure phytoplankton sterol (PCGC/AMS)
measure lignin phenol/plant wax (PCGC/AMS)
stipulate as –1000 ‰
measure phytoplankton sterol (irm-GC-MS)
- assume offset between biomarker and bulk OC
measure lignin phenol/plant wax (irm-GC-MS)
- assume offset between biomarker and bulk OC
assume value based on regional stratigraphy
- (or measure biomarker selected based on Δ14C)
27
Dual Isotope Mass Balance
20
10
Ross Sea (Fairy)
Ross Sea (Emperor)
Ross Sea (Gentoo)
Ross Sea (Chinstra
Gulf Of Mexico
Bermuda Rise
marine
vascular plant
relict
Beaufort Sea
30
Washington Margin St1
40
Washington Margin St2
50
Black Sea Unit II
%
60
Black Sea Unit I
70
Santa Monica Basin
80
14
-251 -160 -108 -468 -600 -194 -136 -570 -876 -300 -395 -555 -712 Δ C TOC
13
-20.7 -23.0 -24.2 -25.36 -22.68 -25.29 -25.24 -21.7 -28.26 -24.04 -27.42 -26.35 -25.65 δ C TOC
Benguela Upwellin
90
Arabian Sea
100
-109
-21.7
0
Ro
Ro
Ro
Ro
B
Sa
Gu
W
Ar
Bla
Be
Be
W
Bla
as
ab
as
rm
ss
ss
ss
ss
lf O eau
ck
h
h
ian ngue nta M ck S
for
ud
Se
Se
Se
Se
Se
fM
e
la
a R ingto ingto
tS
Se
on
a(
a(
a(
a(
ex
Up
e
n
n
ica a Un a Un
a
Fa
Em
G
C
i
se
a
ico
Ma
hin
en
we
Ma
it I
it I
iry
B
pe
too
rgi
str
llin
as
I
)
r
g
r
or)
nS
in
ap
in
g
)
St
)
t2
1
28