Upscaling macro-benthic activity from local diagenesis to biogeochemical cycles

(1)

Upscaling macro-benthic activity from local diagenesis to

biogeochemical cycles

Arthur Capet

1

, Audrey Plante

2

, Lei Chou

2

, Nathalie Fagel

3

, Adrian Teaca

4

, and Marilaure Grégoire

1

_{Modeling for aquatic systems (MAST), ULiege, Belgium,}

2

_{Biogéochimie et modélisation du système Terre, ULB, Belgium,}

3

_{UR AGEs - Argiles, Géochimie et Environnements sédimentaires, ULiege, Belgium,}

4

_{NIRMD, Romania}

The Benthox Project: Objectives & Concepts

To resolve the role and response of macrobenthos in coastal hypoxia dynamics

Work hypotheses

I [O2] shapes the distribution of

benthic populations & activity

I Macrobenthic activity affects

Benthic-Pelagic coupling

Assumptions to conciliate spatial scales

I We use functional traits to

synthetize macrobenthic activity

I We use bentic meta-models to represent diagenesis in a 3D model

Methodology

Conclusions & Perspectives

Conclusions

I Facies of macrobenthic activities are identified from sediment core analyses

I Accounting for diversity in macrobenthic activity affect pelagic biogeochemistry in coupled models

I Restrained irrigation limits benthic denitrification

Perspectives

I Functional Traits-Habitat analyses will be used to set the distribution of facies in the 3D model (see poster by M. Grégoire).

References

1 Capet, A., Meysman, F. J. R., Akoumianaki, I., Soetaert, K. & Grégoire, M. Integrating sediment biogeochemistry into 3D oceanic models: a study of benthic-pelagic coupling in the Black Sea. Ocean Model. (2016).

2 Soetaert, K., Middelburg, J. J., Herman, P. M. J. & Buis, K. On the coupling of benthic and pelagic biogeochemical models. Earth-Sci. Rev. 51, 173–201 (2000).

3 Wijsman, J. W. M., Herman, P. M. J. & Gomoiu, M. T. Spatial distribution in sediment characteristics and benthic activity on the northwestern Black Sea shelf. Mar. Ecol. Prog. Ser. 181, 25–39 (1999).

1D diagenetic calibration

→ Facies of macrobenthic activity

● ● ● ● 15 12 6 7 st10 st1 st17 st2 st23 st25 st30 st3 st11 st14 st16 st18 st19 st20 st22 st24 st26 st28 st29 st31 st6 st15 43 44 45 46 47 27 28 29 30 31 32 lon lat Station ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 12 15 6 7 st1 st10 st11 st14 st15 st16 st17 st18 st19 st2 st20 st22 st23 st24 st25 st26 st28 st29 st3 st30 st31 st4 st5 st6 Campaign ●BTX2016 Wijsman

Domain: The Black Sea northwestern shelf.

Data: porewater nutrient, solid phase, benthic fluxes

Campaigns Wijsman et al., 1995, Emblas2016, Emblas2017

Calibration identifies probability distributions for parameters of the OMEXDIA diagenetic model

(Here: Station 6, Emblas 2016 Campaign)

BioIrrigation − [/d] BioTurbation − [cm2/d] 0.0 0.1 0.2 0.3 0.4 0.0 0.1 0.2 0.3 0.4 −50 −40 −30 −20 −10 0 Depth − [cm] Station 12 6 7

Macrobenthic activity is represented by profiles of

bioturbation (solid phase extra diffusion) and

bioirrigation (non-local exchanges of liquids)

Macrobenthic Facies

→ Meta-Models for Benthic-Pelagic Coupling

pdenit: Part of benthic respiration led by denitrification. Cmin:

Car-bon mineralized per unit of time. bwO2: Bottom Oxygen concentration. Other dimensions are not represented.

← The 1D diagenetic model is run multiples times while

perturb-ing Bottom water nutrients and organic input within ranges

obtained from 3D simulations , and Macrobenthic activity

pa-rameters within ranges obtained during calibrations.

Those simulations are used to adjust meta-model functions, that are implemented in the 3D water-column model to represent the behavior of the 1D diagenetic model.

Set of functions are issued for different facies of macrobenthic → activity, to be used for different regions of the 3D model.

Benthic-Pelagic coupled simulations 1D & 3D

Denitr. in Wat. − [mmol/m2/d] Denitr. in Sed. − [mmol/m2/d]

Flux O2 − [mmol/m2/d] Flux NOx − [mmol/m2/d] Flux NH4 − [mmol/m2/d] Bottom O2 − [mmol/m3] Bottom NOx − [mmol/m3] Bottom NH4 − [mmol/m3]

panox pdenit pnit

0 200 400 600 0 200 400 600 0 200 400 600 0.00 0.25 0.50 0.75 1.00 1.25 5 10 15 20 25 0 1 2 3 0.050 0.075 0.100 0.125 40 60 80 −1.0 −0.5 0.0 0.5 0.4 0.6 0.8 1.0 1.2 0.25 0.50 0.75 1.00 0 100 200 300 −15 −10 −5 0.000 0.025 0.050 0.075 0.100 Time − [d] v alue Station 6 7 12

← The sensitivity of Benthi-Pelagic coupling is explored

with 1D simulations, for

typ-ical shelf conditions.

To mitigate the lack of lateral flows, a weak relaxation to-wards 3D model outputs is im-posed.

The three simulations shown here differ only in terms of macrobenthic facies (see above).

3D simulations resolve the coupled

dynamics of the Black Sea north western shelf. Those are used to reproduce the

diversity of benthic-pelagic coupling (above) and the dynamics of seasonal hypoxia (right).