Do burrowing organisms influence carbon processing on a global scale? A data mining approach.

Frank Bockelmann Olivier Maire Filip Meysman

Laboratory of Analytical and Environmental ChemistryVrije Universiteit Brussel (VUB)Pleinlaan 2, 1050 Brussel

fbockelm@vub.ac.be

www.vub.ac.be/ANCH

1. Burrowing organisms in marine environments A fresh look at Darwin‘s last idea

2. Carbon cycling in the oceanThe role of the seafloor

3. Does macrofaunal activity affect organic matter processing on a global scale?A data mining approach

4. Preliminary results

OUTLINE

1. Burrowing organisms in marine environmentsA fresh look at Darwin‘s last idea

Charles Darwin*12 Feb 1809, †19 Apr 1882

1. A fresh look at Darwin’s last idea

1. A fresh look at Darwin’s last idea

Bioturbation is the displacement and mixing of sediment particles by benthic animals or rooting plants resulting in disturbance of sediment layers.

Solan et al., MEPS (2004)

Spidercrab (Hyas araneus)

1. A fresh look at Darwin’s last idea

Bioirrigation is the process of benthic organisms flushing their burrows with seawater thereby exchanging dissolved substances between the porewater and overlying seawater.

Brittle star

0

20

40

60

80

100

120

0 20 25 40 45 55 60 65 75 100 115 145 150 175 180 190 195 200 205 215 220

Time (sec)

% a

ir s

atu

rati

on

Stahl & Glud, L&O (2006)

Evolution O2 concentration at particular point

1. A fresh look at Darwin’s last idea

Ocean floor without fauna

O2 SO4

Anoxic sediment

5 mm

• microbial mats• shallow O2 penetration• diffusive transport

10 cm

• ventilated burrow systems • increased O2 supply• biol. mediated transport

Ocean floor with fauna

1. A fresh look at Darwin’s last idea

after Meysman, et al., Trends Ecol. Evol. (2006)

Slide 02/15

2. Carbon cycling in the ocean The role of the seafloor

Atmosphere

Deep Ocean

Deepsediment

Surface sediment

Upper ocean

0.4%

5%

4.6%

CO2 + H2O CH2O + O2

Recycling

15%

80%

Carbon fixation (~54 Pg yr-1)

CO2 + H2O CH2O + O2

ExportRelease

Burial

200 m

after Sarmiento and Gruber, 2006

Slide 02/15

Organic carbon sequestration

Oxygen accumulation

CO2 sequestration

CO2 O2

CH2O

2. Carbon cycling – The role of the seafloor

2. Carbon cycling – The role of the seafloor

Return CO2 towater column

2 2 2 2CH O O CO H O

Sequestration in deeper sediments

92 %

8 %

Seafloor flux

The seafloor – An efficient „batch reactor“ Total area: ~ 362 Mio km2

Reservoir size: 150*1015 gC Turnover time: 0.1 – 1000 yr

redrawn from Seiter et al., DSRII (2004)

Critical questions to be asked... How much carbon goes, how much stays?

How does this efficiency vary between environments?

What controls the recycling efficiency?

2. Carbon cycling – The role of the seafloor

Deep sea Continental margins

Organic matter inputOrganic carbon contentMacrofaunal activity

reproduced from Burdige, Chem. Rev. (2007)

2. Carbon cycling – The role of the seafloor

Is macrofaunal activity a

key player at the global scale?

3. Does macrofaunal activity affect organic matter processing on a global scale?A data mining approach

Data-mining

3. A data mining approach

GIS

Parameterization

Modelling

Quantitative assessment of macrofauna affect on sedimentary carbon cycling at a global scale

2 2 2 2CH O O CO H O

The model parameters in focus

Bioturbation Burial Degradation

Bio-irrigation O2-consumption

3. A data mining approach

The model parameters in focus

Independent variableswater depth

temperature, salinityprimary production

Sediment typeporosity density

sand, silt, clay content

Sediment transportbioturbation coefficient (Db)bioirrigation coefficient (α)

burial velocity (v)mixed layer depth

mass flux to seafloor O2 consumptiondiffusive O2 uptake (DOU)

total O2 uptake (TOU)O2 penetration depth

bottom water O2 content

Organic matterseafloor flux

surface sediment contentburial flux

decay rate constant (k)remineralization flux (ΣCO2)

3. A data mining approach

Sediment O2 uptake

Bioturbation coefficient (Db)

TOUDOU

210Pb 234Th

3. A data mining approach

4. Preliminary results

4. Preliminary results

ETOPO 1 Min. Global Bathymetry (NGDC/NOAA, 2008)

~ 10% < 1000m

4. Preliminary results

Total organic matter degradation (TOU)

Organic matter degradation supported by physical transport only (DOU)

Extra organic matter degradation induced by the presence of fauna(TOU-DOU = FMOU)Glud, Mar. Biol. Rev. (2008)

Sediment O2 uptake as a measure of remineralization

4. Preliminary results

• Globally, TOU accounts for remineralization of 2.74 PgC yr-1 of that 70% DOU and 30% FMOU.

• Continental margins (above 1000m) release 1.84 PgC yr-1 (67% of global Rox) of that 54% DOU and 46% FMOU.

• Shutting down macrofaunal activity at continental margins would result in ~ 5fold increase in C-burial!

FMOU

TOU

30 %

67 %

Things to remember...

• Macrofauna enhances the sediment oxygen uptake through bioturbation and bio-irrigation

• Benthic activity has large effect on local biogeochemistry of the ocean floor (ecosystem engineering)• Continental margin sediments play a crucial role in organic matter processing at a global scale

• (Global) carbon balance estimates are extremely sensitive to the representation of benthic activity

However,• Ocean floor is a more variable environment than

anticipated • Sampling with respect to basal model parameters

tends to exclude large areas (e.g., Db bias to Atlantic; k bias to Pacific)

• A more systematic approach towards deposition of data into repositories is desirable.

Funding throughFWO-Odysseus project to Filip Meysman

"Quantifying Darwin's last idea: the influence of bioturbation on the biogeochemistry of marine

sediments, and its impact on the global carbon cycle"

fbockelm@vub.ac.be www.vub.ac.be/ANCH