insights into seasonal organic carbon … – estuarine organic carbon ... chris sommerfield and bob...

Insights into seasonal organic carbon cycling in the Delaware Estuary from N-alkane biomarkers and stable carbon isotopes

Hermes, A.L. and E.L. Sikes

9:30 AM - 20 January 2013

Session 15 – What’s Mud Got to Do With It?

Delaware Estuary Science and Environmental Summit

Cape May, NJ

Hermes 2

Overview

1. Introduction – Estuarine organic carbon (OC) cycling

– OC cycling in the Delaware Estuary

2. Results – Bulk measurements of surface and bottom waters:

• suspended solid content (SSC) and

• total organic carbon (TOC)

– Alkane biomarkers: algal vs. land-derived OC

– Alkane compound-specific isotopes: marsh vs. terrestrial sources of land-derived OC

3. Summary and Conclusions – Land-derived OC is trapped in the estuarine turbidity maximum (ETM) and

estuarine bottom waters.

– Marsh inputs from the lower estuary are substantial in Delaware Estuary bottom waters and the ETM.

Introduction Results: Bulk, Biomarkers, CSIA Summary & Conclusions

Hermes 3

Algal OC: - Brought in by tidal

pumping - Seasonally produced

within the estuary

Vascular plant (land) OC: • Terrestrial from the

river

Burial

1. What are the sources of OC through the estuary?

2. How are these sources partitioned through estuarine physical, chemical, and biological gradients?

3. What are their fates?

RIVER

OCEAN

Remineralization

WETLANDS

CO2

Estuarine OC cycling links land and sea.

• Marsh from the fringing wetlands


POC

?

Hermes 4

New Jersey

Delaware

Philadelphia

●

Trenton ●

● Wilmington

Pennsylvania

Upper Estuary

Estuarine Turbidity

Maximum

Lower Estuary

Atlantic Ocean

N

�

40.2

40.0

39.8

39.6

39.4

39.2

39.0

38.8

-75.6 -74.8-75.4 -75.2 -75.0

ETM – algal and

terrestrial

Mismatch between observed wetland erosion and geochemical analyses?

Previous work – Surface waters This work – Surface and Bottom waters

1. The Delaware River is the primary source of freshwater, sediments, and land-derived OC (e.g. Cook et al., 2007;

Mannino and Harvey, 1999).

2. Seasonal algal blooms occur in Delaware Bay and the upper freshwater river (e.g. Pennock and Sharp,

1986; Cifuentes et al., 1988). 1. The ETM is a mud trap and mixing

zone for OC (e.g. Biggs et al., 1983;

Sommerfield and Wong, 2011; Mannino and

Harvey, 1999).

2. Marsh OC is not significant in the Delaware Estuary (e.g. Cifuentes, 1991;

Mannino and Harvey, 1999).


The Delaware Estuary is a model system to assess OC cycling.

Hermes 5

Suspended solid content (SSC) identifies the ETM.

S’10- DRY

M’11- WET

Ocean River Distance (km)

SSC (mg/L)

Bottom water Surface water

More OC in bottom water than surface water!


SSC data courtesy of the University of Delaware

0

100

200

300

400

500

600

-20 10 40 70 100 130 160 190

0

200

400

600

-20 10 40 70 100 130 160 190

0

200

400

600

800

1000

-20 10 40 70 100 130 160 190

0

200

400

600

800

1000

-20 10 40 70 100 130 160 190

POC (μM)


Hermes 6

Algal OC Land OC = marsh and terrestrial

0

5

10

15

20

25

30

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

% T

ota

l alk

ane

s

Alkane chain length ( # Carbons)

Algae Marsh plant Terrestrial

Nonacosane (C29), Eglinton and Hamilton, Science, 1967


Alkane biomarkers trace algal vs. land plant OC.

Hermes 7

0

100

200

300

400

500

600

-20 10 40 70 100 130 160 190

0

200

400

600

-20 10 40 70 100 130 160 190

S’10

M’11


SSC (mg/L)


SSC data courtesy of the University of Delaware

0

200

400

600

800

1000

-20 10 40 70 100 130 160 190

0

200

400

600

800

1000

-20 10 40 70 100 130 160 190

POC (μM)


Land OC = marsh & terrestrial Algal OC

0

1,000

2,000

3,000

4,000

5,000

-20 10 40 70 100 130 160 190

0

2,000

4,000

6,000

8,000

10,000

12,000

-20 10 40 70 100 130 160 190

Alkane abundance (ng/L)


The OC in bottom waters of the ETM is primarily land-derived OC!

Bottom water Surface water

Hermes 8

http://ian.umces.edu/imagelibrary/displayimage-3283.html

Partnership for the Delaware Estuary, 2012

Marsh

Terrestrial

New Jersey

Delaware

Philadelphia

●

Trenton ●

● Wilmington

Pennsylvania

Upper Estuary

Estuarine Turbidity

Maximum

Lower Estuary

Atlantic Ocean

N

�

40.2

40.0

39.8

39.6

39.4

39.2

39.0

38.8

-75.6 -74.8-75.4 -75.2 -75.0C4

Marsh and terrestrial land OC have different delivery pathways.


C3

C3

Hermes 9

-40

-38

-36

-34

-32

-30

-28

-26

-24

-22

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

The compound-specific stable carbon isotopic composition of alkanes differentiates C3 and C4 land-derived OC.

Alk

ane

1

3C

(‰

PD

B)

Alkane chain length (# Carbons)


C4

C3

Salt/brackish marsh, e.g. Spartina sp.

Freshwater marsh, e.g. Phragmites sp.

Terrestrial-derived riverine detritus

Hermes 10

Alkane isotopes require C4 inputs. C4 inputs increase down-estuary: C4 marsh inputs are important in the Delaware Estuary!


Alk

ane

1

3C

(‰

PD

B)

Chloro. max

ETM

River

~35-65% of land plant OC is from C4

~15-50% of land plant OC is from C4

Alkane chain length (# Carbons)

S’10 - Dry

M’11 - Wet

-40

-36

-32

-28

-24

23 24 25 26 27 28 29 30 31 32 33

-40

-36

-32

-28

-24

23 24 25 26 27 28 29 30 31 32 33

C3

C4

-38

-36

-34

-32

-30

-28

-26

-24

-22

23 24 25 26 27 28 29 30 31 32 33

March 2011

River - 100% C3

ETM - ~15-47% C4

DB - ~32-49% C4

Chloro. max

ETM

River

Hermes 11

Lateral circulation demonstrated by numerical model output provides a mechanism for C4 marsh inputs.

Flood

+NJ -DE

Ebb

+NJ -DE

Model output courtesy of M. Aristizabal

For more, see Maria’s talk during the Physical Processes Session 17 (up next!)


Hermes 12

New Jersey

Delaware

Philadelphia

●

Trenton ●

● Wilmington

Pennsylvania

Upper Estuary

Estuarine Turbidity

Maximum

Lower Estuary

Atlantic Ocean

N

�

40.2

40.0

39.8

39.6

39.4

39.2

39.0

38.8

-75.6 -74.8-75.4 -75.2 -75.0

September2010- Late summer, low discharge


Marsh Terrestrial

Algal

Hermes 13

New Jersey

Delaware

Philadelphia

●

Trenton ●

● Wilmington

Pennsylvania

Upper Estuary

Estuarine Turbidity

Maximum

Lower Estuary

Atlantic Ocean

N

�

40.2

40.0

39.8

39.6

39.4

39.2

39.0

38.8

-75.6 -74.8-75.4 -75.2 -75.0

March 2011- Spring bloom, after freshets


Marsh Terrestrial

Algal

Hermes 14

Summary and Conclusions: A new perspective of estuarine OC cycling

• There is more carbon in bottom waters than surface waters in the Delaware Estuary.

• The composition of bottom water is different than surface waters – it’s derived from the land.

• Compound-specific isotopes of biomarkers allow us to assess the role of wetlands in the Delaware Estuary.

• Wetland OC influences the geochemical signatures of OC pools in the Delaware Estuary, especially within bottom waters of the ETM.


Hermes 15

Acknowledgements

Liz Sikes (advisor) Chris Sommerfield and Bob Chant, Co-PIs Liz Canuel (committee; VIMS) Eli Hunter Cap’n and crew of the R/V Hugh Sharp Gear: Lee Kerkhof, Lora McGuinness, Kay Bidle, Oscar Schofield, Matt Oliver

Lab and Cruise assistance: Michelle Hardee, Aurora Elmore, Benedetto Schiraldi, Chelsea Martin, Alyssa Karis, Drew Webster, Dove Guo, Maria Aristizabal, Joe Jurisa, Aboozar Tabatabai, Alex Lopez, Jack McSweeney, Brandon Boyd, Zac Duval, Dack Stewart, John Biddle, Clare Entwistle, Rachel Doery

Hermes 16

Hermes 17

New Jersey

Delaware

Philadelphia

●

Trenton ●

● Wilmington

Pennsylvania

Upper Estuary

Estuarine Turbidity

Maximum

Lower Estuary

Atlantic Ocean

N

�

40.2

40.0

39.8

39.6

39.4

39.2

39.0

38.8

-75.6 -74.8-75.4 -75.2 -75.0

Riverine Endmember

Marine Endmember

Delaware Bay (Chlorophyll Maximum)

ETM

Surface and bottom water sampling targeted 4 zones of geochemical interest for biomarker analyses.


Hermes 18

The Average Chain Length (ACL) index differentiates algal and vascular plant (land) OC.

0

5

10

15

20

25

30

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

% T

ota

l alk

ane

s

Alkane chain length (# carbon atoms)

More vascular plant OC More

algal OC


Hermes 19

20

22

24

26

28

30

-30 -25 -20 -15 -10

AC

L

C3 vascular plant

Marine Algal OC

C4 marsh

Bulk 13C-POC (‰ PDB)

F.W. Algal OC


Hermes 20

20

21

22

23

24

25

26

27

28

29

30

-30 -27 -24 -21 -18 -15

20

21

22

23

24

25

26

27

28

29

30

-30 -27 -24 -21 -18 -15

Surface water is imprinted by seasonal algal OC throughout the estuary, but bottom water is consistently dominated by land OC.

Surface Water Bottom Water

Ocean Bay ETM River

C3 vascular plant

Marine Algal OC

C4 marsh

F.W. Algal OC

C3 vascular plant

Marine Algal OC

C4 marsh

F.W. Algal OC


AC

L


Sept. March

Hermes 21

20

21

22

23

24

25

26

27

28

29

30

-30 -27 -24 -21 -18 -15

20

21

22

23

24

25

26

27

28

29

30

-30 -27 -24 -21 -18 -15

Surface water is imprinted by seasonal algal OC throughout the estuary, but bottom water is consistently dominated by land OC.


Surface Water Bottom Water

Ocean Bay

March June Sept. Dec. March

ETM River

C3 vascular plant

Marine Algal OC

C4 marsh

F.W. Algal OC

C3 vascular plant

Marine Algal OC

C4 marsh

F.W. Algal OC


AC

L

Hermes 22

Summary and Conclusions: A new perspective of estuarine OC cycling

• There is more carbon in bottom waters than surface waters in the Delaware Estuary.

• The ETM traps vascular plant material, and as a reactor for OC processing, may fuel remineralization of terrestrial-derived OC, contributing to the net heterotrophy of estuaries.

• Bottom water geochemical signatures, especially in the ETM, are imprinted by marsh OC, which is delivered to the estuary via lateral circulation.

• The land-derived OC reaching the marine OC cycle may have a different reactivity than previously thought due to its different pathway of delivery.


Hermes 23

Delaware Estuary Wet Chemistry Flow Chart

POM or sediment sample + internal

recovery standards in

ASE cells

Both extracts individually

saponified with

methanolic KOH

Total Fatty Acids

Saponified neutrals

Supernatant

Extract 1: Neutral compound

extract

(100% Hexane v/v)

Bottom fraction

Extract 2: Polar compound

extract (1:4

Chloroform:MetOH v/v)

Dual ASE Extraction Transesterification

Phospholipid fatty acid methyl

esters

Alkanes and Sterols

1

2

Total Fatty Acids

Saponified neutrals

Supernatant

Bottom fraction

Saponification Step 2 with HCl

Neutral Fatty Acids

Polar Neutrals

Wet chemistry flow chart

Results - 2

Hermes 24

Sediments in the upper estuary are strongly terrestrial.

20

21

22

23

24

25

26

27

28

29

30

0 1 2 3 4 5 6

ACL

CPI

Hermes 25

010

2533

50

60

66

75

100

0

0.5

1

1.5

2

2.5

0 1 2 3 4 5 6 7

MTI

CPI-LC(C25-C34)

Mar'10S Mar'10B June'10S June'10B Sept'10S Sept'10B

Dec'10S Dec'10B Mar'11S Mar'11B Mar'100-1 Sept'10floc

Sept'100-1 Mar'11floc Mar'110-1 endmembers

Hermes 26

0

5

10

15

20

25

30

161718192021222324252627282930313233343536

Alkan

e%

AlkaneChainLength

A+M+T

0

5

10

15

20

25

30

161718192021222324252627282930313233343536

Alkan

e%

AlkaneChainLength

50%A+50%T

0

5

10

15

20

25

30

161718192021222324252627282930313233343536

Alkan

e%

AlkaneChainLength

50%T+50%M

0

5

10

15

20

25

30

161718192021222324252627282930313233343536

Alkan

e%

AlkaneChainLength

75%T+25%M

0

5

10

15

20

25

30

161718192021222324252627282930313233343536

Alkan

e%

AlkaneChainLength

25%T+75%M

0

5

10

15

20

25

30

161718192021222324252627282930313233343536

Alkan

e%

AlkaneChainLength

2/3T+1/3M

Hermes 27

0

10

20

30

40

161718192021222324252627282930313233343536

%ofTo

talA

lkan

es

AlkaneCarbonChainLength

May-FlowerandStem

0

5

10

15

20

25

161718192021222324252627282930313233343536

%ofTo

talA

lkan

es


May-RootandStem

0

10

20

30

40

50

161718192021222324252627282930313233343536

%ofTo

talA

lkan

es


May-StemandLeaf

0

10

20

30

40

50

60

161718192021222324252627282930313233343536

%ofTo

talA

lkan

es


October-StemandLeaf

0

5

10

15

20

25

30

161718192021222324252627282930313233343536

%ofTo

talA

lkan

es


October-Flower

0

10

20

30

40

50

161718192021222324252627282930313233343536

%ofTo

talA

lkan

es


October-Leafalone

0

5

10

15

20

25

30

161718192021222324252627282930313233343536

%ofTo

talA

lkan

es


Composite

Hermes 28

Hermes 29

0

30

60

90

120

150

16171819202122232425262728293031323334353637383940

ugalkane/gOC

MarineEndmember-SurfaceWater

Jun10ME

Sept10ME

Dec10ME

Mar11ME

Mar10ME

0

50

100

150

200

250

16171819202122232425262728293031323334353637383940

ugalkane/gOC

MarineEndmember-Bo omWater

Jun10ME

Sept10ME

Dec10ME

Mar11ME

Mar10ME

0

30

60

90

120

150

16171819202122232425262728293031323334353637383940

ugalkane/gOC

DelawareBay-SurfaceWater

Jun10CM

Sept10CM

Mar11CM

Dec10ST

Mar10CM

0

30

60

90

120

150

16171819202122232425262728293031323334353637383940

ugalkane/gOC

DelawareBay-Bo omWater

Jun10CM

Sept10CM

Dec10ST

Mar11CM

Mar10CM

0

50

100

150

200

250

300

16171819202122232425262728293031323334353637383940

mgalkane/gOC

ETM-SurfaceWaterJun10ETM

Sept10ETM(13)

Sept10ETM(17)

Dec10ETM

Mar11ETM(9)

Mar11ETM(11)

Mar10ETM

Sept10IM(15)

0

50

100

150

200

250

300

16171819202122232425262728293031323334353637383940

ugalkane/gOC

ETM-Bo omWaterJun10ETM

Sept10ETM(13)

Sept10ETM(17)

Dec10ETM

Mar11ETM(9)

Mar11ETM(11)

Mar10ETM

Sept10IM(15)

0

50

100

150

200

250

300

350

400

16171819202122232425262728293031323334353637383940

mgalkane/gOC

RE-SurfaceWater

Jun10ME

Sept10ME

Dec10ME

Mar11ME

Mar10ME

0

100

200

300

400

500

600

700

800

16171819202122232425262728293031323334353637383940

ugalkane/gOC

RE-Bo omWater

Jun10RE

Sept10RE

Dec10RE

Mar11RE

Mar10RE

Hermes 30

0

500

1,000

1,500

2,000

2,500

3,000

-20 30 80 130 180 Alk

an

e a

bu

nd

an

ce

(m

g/g

OC

) March 2010

0

200

400

600

800

1,000

1,200

-20 30 80 130 180

June 2010

0 100 200 300 400 500 600 700 800 900

1,000

-20 30 80 130 180

September 2010

0

200

400

600

800

1,000

1,200

-20 30 80 130 180

Alk

an

e a

bu

nd

an

ce

(m

g/g

OC

)

Distance from Estuary mouth (km)

December 2010

0

500

1,000

1,500

2,000

2,500

-20 80 180

March 2011

Bottom water

Surface water

Land OC – marsh + terrestrial

Algal OC

Hermes 31

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 20 40 60 80 100

Alkan

eabundan

ce(ng/L)

%Freshwater

September2010

0

2,000

4,000

6,000

8,000

10,000

12,000

0 20 40 60 80 100

Alkan

eabundan

ce(ng/L)

%Freshwater

March2011

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

0 20 40 60 80 100

Alkan

eabundan

ce(ng/L)

%Freshwater

December2010

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 20 40 60 80 100

Alkan

eabundan

ce(ng/L)

%Freshwater

June2010

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 20 40 60 80 100

Alkan

eabundan

ce(ng/L)

%Freshwater

March2010

Bottom water

Surface water

Land OC – marsh + terrestrial

Algal OC

Hermes 32

0

10

20

30

40

50

60

70

80

90

100

-20 0 20 40 60 80 100 120 140 160 180 200

%C

org

DistancefromEstuaryMouth(km)

Mar10-S

Mar10-B

June-S

June-B

Sept-S

Sept-B

Dec-S

Dec-B

Mar11-S

Mar11-B

March June Sept. Dec. March

Hermes 33

Reasons why:

• Well-studied

• Archetypal coastal plain estuary

• Multiple sources of OC

– Terrestrial OC from Delaware River

– Algal OC from seasonal blooms

– Extensive wetlands – marsh OC

• ETM – particle trap and MIXING ZONE! (Sommerfield and Wong, 2011, J. of Geophys. Res.)

The Delaware Estuary is a model system to assess OC cycling.

New Jersey

Delaware

Philadelphia

●

Trenton ●

● Wilmington

Pennsylvania

Upper Estuary

Estuarine Turbidity

Maximum

Lower Estuary

Atlantic Ocean

N

�

40.2

40.0

39.8

39.6

39.4

39.2

39.0

38.8

-75.6 -74.8-75.4 -75.2 -75.0

Map courtesy of C. Sommerfield, redrafted


Hermes 34

0

200

400

600

800

1000

-20 30 80 130 180

Suspended solid content (SSC) matched in situ optical backscatter.

0

100

200

300

400

500

600

-20 30 80 130 180

0

100

200

300

400

500

600

-20 30 80 130 180

S’10 (fall)

M’11 (spring)


SSC (mg/L) POC (μM)

Bottom water

Surface water

More OC in bottom water than surface water!


SSC

da

ta c

ou

rtes

y t

he

Un

iver

sity

of

Del

aw

are

0

200

400

600

800

1000

-20 30 80 130 180


Hermes 35

CM ETM

-30

-25

-20

-15

-30

-25

-20

-15

-20 0 20 40 60 80 100 120 140 160 180 200

M - 2011

Ocean River

Bu

lk

13C

-PO

C (

‰ P

DB)

Distance (km)

-30

-28

-26

-24

-22

-20

-18

-16

-14

-12

-20 0 20 40 60 80 100 120 140 160 180 200

Ocean River

Bu

lk

13C

-PO

C (

‰ P

DB)

The bulk stable carbon isotopic composition of POC differentiates seasonal algal blooms in the lower

estuary and C3 vascular plant OM in the upper estuary.

S

M

Distance (km)


Bottom water

Surface water

Hermes 36

• Preen and Kirchman 2004

insights into seasonal organic carbon … – estuarine organic carbon ... chris sommerfield and bob...

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