Download - Do burrowing organisms influence carbon processing on a global scale? A data mining approach
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
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
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60
80
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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"
[email protected] www.vub.ac.be/ANCH