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

1. 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 Chemistry Vrije Universiteit Brussel (VUB) Pleinlaan 2, 1050 Brussel fbockelm@vub.ac.be www.vub.ac.be/ANCH

2. OUTLINE • 1. Burrowing organisms in marine environments • A fresh look at Darwin‘s last idea • Carbon cycling in the ocean • The role of the seafloor • 3. Does macrofaunal activity affect organic matter processing on a global scale? • A data mining approach • 4. Preliminary results

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

4. 1. A fresh look at Darwin’s last idea Charles Darwin *12 Feb 1809, †19 Apr 1882

5. 1. A fresh look at Darwin’s last idea

6. 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. Spidercrab (Hyas araneus) Solan et al., MEPS (2004)

7. 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. Evolution O2 concentration at particular point Brittle star Stahl & Glud,L&O (2006)

8. 1. A fresh look at Darwin’s last idea Ocean floor without fauna Ocean floor with fauna O2 SO4 5 mm 10 cm Anoxic sediment • microbial mats • shallow O2 penetration • diffusive transport • ventilated burrow systems • increased O2 supply • biol. mediated transport after Meysman, et al., Trends Ecol. Evol. (2006)

9. 2. Carbon cycling in the ocean The role of the seafloor Slide 02/15

10. 2. Carbon cycling – The role of the seafloor CO2 sequestration Oxygen accumulation Carbon fixation(~54 Pg yr-1) O2 CO2 + H2O CH2O + O2 CO2 80% 200 m 15% Release Export 5% Recycling CH2O CO2 + H2O CH2O + O2 4.6% Burial Organic carbon sequestration 0.4% Atmosphere Upper ocean Deep Ocean Surface sediment Deep sediment after Sarmiento and Gruber, 2006 Slide 02/15

11. 2. Carbon cycling – The role of the seafloor The seafloor – An efficient „batch reactor“ Total area: ~ 362 Mio km2 Reservoir size: 150*1015 gC Turnover time: 0.1 – 1000 yr Return CO2 to water column Seafloor flux 92 % 8 % Sequestration in deeper sediments

12. 2. Carbon cycling – The role of the seafloor Organic matter input Organic carbon content Macrofaunal activity Deep sea Continental margins Critical questions to be asked... How much carbon goes, how much stays? How does this efficiency vary between environments? What controls the recycling efficiency? redrawn from Seiter et al., DSRII (2004)

13. 2. Carbon cycling – The role of the seafloor Is macrofaunal activity a key player at the global scale? reproduced from Burdige, Chem. Rev. (2007)

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

15. 3. A data mining approach Data-mining GIS Parameterization Modelling Quantitative assessment of macrofauna affect on sedimentary carbon cycling at a global scale

16. 3. A data mining approach Degradation Burial Bioturbation O2-consumption Bio-irrigation The model parameters in focus

17. 3. A data mining approach Independent variables water depth temperature, salinity primary production Organic matter seafloor flux surface sediment content burial flux decay rate constant (k) remineralization flux (ΣCO2) Sediment transport bioturbation coefficient (Db) bioirrigation coefficient (α) burial velocity (v) mixed layer depth mass flux to seafloor O2 consumption diffusive O2 uptake (DOU) total O2 uptake (TOU) O2 penetration depth bottom water O2 content Sediment type porosity density sand, silt, clay content The model parameters in focus

18. 3. A data mining approach Sediment O2 uptake TOU DOU Bioturbation coefficient (Db) 210Pb 234Th

19. 4. Preliminary results

20. 4. Preliminary results ETOPO 1 Min. Global Bathymetry (NGDC/NOAA, 2008) ~ 10% < 1000m

21. 4. Preliminary results Extra organic matter degradation induced by the presence of fauna (TOU-DOU = FMOU) Sediment O2 uptake as a measure of remineralization Organic matter degradation supported by physical transport only (DOU) Total organic matter degradation (TOU) Glud, Mar. Biol. Rev. (2008)

22. 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! 67 % TOU FMOU 30 %

23. 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.

24. Funding through FWO-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