Organics at 40o S (D357)

Maite Hernández/Rich Pancost

PHYTOPLANKTON BIOMARKERS

O

C37-C39 Ethyl and methyl ketones: Alkenones

Brassicasterol

OH

24-methylcholesta-5,24(28)-dien-3β-ol

OH cholesta-5,22-dien-3β-ol

24-ethylcholesta-5,24(28)-dien-3β-olOH

OH

24-propylcholesta-5,24(28)-dien-3β-ol

Prasinophyceae

Crysophyceae

OH

24-methylcholesta-5,22-dien-3b-ol

Source organism

Preserved

+ =

Paleo proxy calibration

Paleo Proxy

Is PP reflected in underlying sediments?

• Lipid distributions reflect productivity variations (Lee and Wakeham, 1988; Hernández-Sánchez et al., 2010).

Coccolithophorids

Diatoms

Alkenones

Sterols

Paleo proxy calibration

• Is PP reflected in underlying sediments?: Potential for community assemblage proxy

Source organism

Preserved

+ = Paleo Proxy

Longitude (˚E)

−45˚

−40˚

−35˚

−30˚

−25˚

St 1St 3

St 6

St 8

St 11

St 13

−10˚ 0˚ 10˚ 20˚

Latit

ude

( ˚S)

−8000

−6000

−4000

−2000

0Depht (m)

SBiomarker distributions inSurface waters

Longitude (˚E)

−45˚

−40˚

−35˚

−30˚

−25˚

St 1St 3

St 6 St 11

−10˚ 0˚ 10˚ 20˚

Latit

ude

(S̊

)

−8000

−6000

−4000

−2000

0Depht (m

Biomarker distributions indeep waters

Longitude (˚E)

−45˚

−40˚

−35˚

−30˚

−25˚

St 1St 3

St 6

St 8

St 11

St 13

−10˚ 0˚ 10˚ 20˚

Latit

ude

( ˚S)

−8000

−6000

−4000

−2000

0Depht (m)

SBiomarker distributions inSurface sediments

Why so different?

Seasonal bias

Degradation

- Hardman-Mounford et al. (2003) chl-a data: weak seasonality at St. 6 and St. 11

Longitude (˚E)

−45˚

−40˚

−35˚

−30˚

−25˚

St 1St 3

St 6

St 8

St 11

St 13

−10˚ 0˚ 10˚ 20˚

Latit

ude

( ˚S)

−8000

−6000

−4000

−2000

0Depht (m)

S

Vertical Fluxes

230Thxs

Summary

- Biomarker distributions in upper water column suggests homogeneous productivity

- Distributions strikingly different in sediments- Most degradation occurs throughout the water

column and/or sediment-water interface- Alkenones, hydroxy methyl alkanoates and diols

seem to be the most diagenetically stable.

- Subtle differences in [O2] seem to have an effect on preservation

To do …

• Biomarker distributions represent community structure in surface waters.

– Heather Bounman and Tom

• Estimate vertical fluxes.

– Gideon Henderson and Alex Thomas

Paleo proxy calibration• Is PP reflected in underlying sediments?:

- Hernandez-Sanchez et al. (Pancost, Henderson, Homoky, Bounman, Thomas +). GCA?

• GDGT distributions in the water column: Implications for the TEX86 paleothermometry proxy- Hernandez-Sanchez, M. T., Woodward, M., Taylor, K. W., Henderson, G., Pancost, R. D., GDGT distributions in SE Atlantic sediments match those in subsurface waters: Geology (to be submitted)

Other outcomes• Hernandez-Sanchez, M. T., and Pancost, R. D. Occurrence of

1-O-monoalkyl glycerol ether lipids in both marine waters and sediments (in prep.)

Thanks for your attention!