1. Primary production and the carbonate system in the Mediterranean Sea
The 45th International Liège Colloquium
Liège, Belgium 13th – 17th May 2013
Primary production and the carbonate system in the Mediterranean Sea
Cossarini G., Lazzari P., Solidoro C.
OGS – National Institute of Oceanography and Experimental Geophysics
Trieste (Italy)

2. Introduction: understanding Ocean Acidification calls for the resolution of the carbonate system and its variability
Carbonate system: DIC (CT) and Alkalinity (AT)
Few data on carbonate chemistry are available for the Mediterranean Sea
Intense gradients from west to east
Touratier and Goyet, 2012

3. Introduction: Mediterranean Sea circulation and boundaries
Anti estuarine circulation at Gibraltar
Surface circulation
Siokou-Frangou et al., 2010
Input from Dardanelles:
Alk mol/y
DIC gC/y
Chopin-Montegut, 1993
Input from rivers:
Alk mol/y
DIC gC/y
Meybeck and Ragu, 1995;
Ludwig et al., 2009 Po
Rhone
Ebro
Dardanelles
Alkalinity profile at Gibraltar
Huertas et al., 2009
Nile

4. Introduction: spatial variability of trophic conditions
Integrated vertical net primary production
Controlling mechanism: extinction factor coefficient (k)
Declining DCM moving eastward
NWM
TYR
ALB
SWE
ION
LEV
Longitudinal and latitudinal transects of chlorophyll a
Lazzari et al., 2012

5. Aim: evaluate scales of variability of carbonate system (DIC and alkalinity) in the Mediterranean Sea and quantify the contribution of physical & biological processes
3D physical-biogeochemical model: OPATM-BFM
Reconstruction of alkalinity and DIC spatial patterns & validation
Decomposition of physical and biological contributions on spatial and temporal variability
Air-sea CO2 exchanges

6. Method: 3D coupled OPATM-BFM-carbonate model
Carbonate system
OCMIP II model
Orr et al., 1999
Wolf-Gladrow et al., 2007
Schneider et al.1999 Wanninkhof,1992
Nutrients
Consumption/production
Alkalinity:
Production: denitrification
phytoplankton uptake of NO3- and PO43-
mineralization and realise of NH4+
Consuption: phytoplankton uptake of NH4+
nitrification
mineralization and realise of PO43-
DIC=[CO2]+[HCO3-]+[CO32-]
consumption:photosynthesys
production: respiration by phyoplankton,
zooplankton and bacterial functional type groups
BFM – Biogeochemical Flux Model
Atmopheric pCO2= ppm
Physical and biogeochemical setup and validation
Beranger et al., 2010; Lazzari et al & poster Lazzari et al

7. Results: Alkalinity – spatial patterns and validation1 2 3 1 5 4 6
Taylor Diagram: B0, B400, B1000: Boum 2008 cruise at 0, 400 and 1000 m; M0,M400, M1000: Meteor51 cruise at 0, 400 and 1000 m; Sm0, Sm400, So0, So400 Sesame dataset at 0 and 400 m, March and October cruises; P0: Prosope cruise, Dyf0, Dyf400, Dyf1000: Dyfamed site at 0, 400 and 1000 m.
mmol/kg 2 3 4 5 6

8. Results: DIC – spatial pattern and validation1 2 3 1 5 4 6
Taylor Diagram: B0, B400, B1000: Boum 2008 cruise at 0, 400 and 1000 m; M0,M400, M1000: Meteor51 cruise at 0, 400 and 1000 m; Sm0, Sm400, So0, So400 Sesame cruises at 0 and 400 m, March and October cruises; P0: Prosope cruise, Dyf0, Dyf400, Dyf1000: Dyfamed site at 0,400 and 1000m.
mmol/kg 2 3 4 5 6

9. Results: spatial variability DIC along W-E transect and its temporal variability
NWM
TYR
ALB
SWM
ION
LEV
Annual average DIC concentration
Amplitude of the seasonal cycle
 DpH =
Latitudinal transect
Longitudinal transect

10. Results: biological and physical contributions on DIC
NWM
Decomposition of physical and biological part of the amplitude of the seasonal cycle
TYR
ALB
SWM
ION
LEV
variability of biological fluxes
[mmol/m3/d]
variability of physical fluxes:
[mmol/m3/d]
flux at air-sea interface, advection and diffusion

11. Results: biological and physical contributions on DIC
NWM
Decomposition of physical and biological annual average fluxes
TYR
ALB
SWM
ION
LEV
Biological carbon pump
Photosynthesis - respiration
physical process
Upwelling transport and diffusion of the adsorbed atmospheric CO2

12. Results: biological and physical contributions on DIC
NWM
Decomposition of physical and biological effects: average annual signal
TYR
ALB
SWM
ION
LEV
Biological carbon pump
Photosynthesis - Respiration
Seasonal cycle of phytoplankton production and community respiration
mmol/m3/d
mmol/m3/d

13. Results: CO2 flux at air-sea interface
OPATM-BFM:
sink of 1.6 x 1012 mol/y
(-0.65 mol/m2/y)
Other estimates:
x 1012 mol/y
Copin-Montegut, 1993
2.1 x 1012mol/y
Huertas et al., 2009
Sink
molC/m2/y
source
From D’Ortenzio et al., 2009

14. Results: CO2 flux at air-sea interface
OPATM-BFM:
sink of 1.6 x 1012 mol/y
(-0.65 mol/m2/y)
Sink
molC/m2/y
source
Switching off the biology from the system
-20% of atmospheric CO2 sink
 quantification (€) of the role of biology (ecosystem service) in carbon cycle

15. Conclusions:
Mediterranean sea has strong spatial variability of carbonate system (model can help in reconstructioning patterns)
Physical processes impact the spatial and temporal variability
Biology has lower effect on seasonal scale but impacts on longer time scale
CO2 flux affected by biological pump (~20%) at the present atmospheric pCO2 conditions

16. THANK YOU Reseach founded by http://medsea-project.eu/