EGU General Assembly 2013 Vienna Austria OS 4

EGU General Assembly 2013, Vienna, Austria OS 4. 4 – Physical and biogeochemical modeling: development, applications, assessment POSTER B 760 PCB modeling in the Gulf of Lions using a 3 D coupled model Alekseenko E. , Thouvenin B. , Tixier C. , Tronczynski J. , Loizeau V. , Garreau P. , Verney R. , Carlotti F. , Espinasse B. , Queguiner B. , and Baklouti M. Contacting e-mail: lena. alekseenko@gmail. com

Modeling strategy Model of hydrodynamics – MARS 3 D ØNavier-Stokes equations + Boussinesq approximation with the hydrostatic assumption (Lazure and Dumas, 2008) ØUsed in Previmer operational (http: //www. previmer. org/en) forecast Model of hydrodynamics (MARS 3 D, Ifremer) system ØValidated in the Gulf of Lions (Go. L) by comparing with Øin-situ (Andre et al. , 2009) Øsatellite data (Andre et al. , 2005) Øsatellite data and drifter trajectories (Nicolle et al. , 2009). Biogeochemical model(Eco 3 M, MIO) Biogeochemical model – Eco 3 M Ø 34 variables including 6 species of organisms Model of PCB trasport ØThe PCB fluxes along the trophic chain are related to carbon fluxes; ØVariable stoichiometry of organisms (Baklouti et at, 2006 a, b) ØModel is validated (Alekseenko et al. , 2013, in progress) by comparing with Øin-situ data Øsatelite Chl-a data Øpublished data PCB transport Ø Each compartment contain also PCB (15 additional variables) ØThe order of magnitudes of the modeled results are coherent with measurements

Biogeochemical model: basic schema Interest of such model for the Mediterranean specificities: - Formulations based on mechanistic processes and already proven in other studies - Multi-limitation of growth (C and / or N, and / or P following areas) - Suitable for both oligotrophic areas (open) and eutrophic (coast) - Allows to study the particular stoichiometry of the Mediterranean

Biogeochemical model. Temporal variations in average Chl-a over space in the NW Mediterranean Sea

Biogeochemical model. Model results vs COSTEAU 4 and COSTEAU 6 in-situ data of Chl-a in mg/m 3 Sea surface Chl-a simulation COSTEAU 4 27/04 -02/05 2010 Averaged in 100 m Chl-a simulation COSTEAU 6 23/01 -27/01 2011

PCB transport model. General proccesses of the PCB transfert Berrojalbiz et al, 2011

PCB transport model: basic schema 3 types of PCBs: (a) in a «free» dissolved form, and dissolved for associated to DOM, PCBq (b) assosiated to POM or (c) living matter «PCB» - PCB assimilated by the organism from grazing PCB « PCBq» - PCB sorbed by adsorption/desorption or passive uptake

PCB 153. Spatial PCB distribution: modeled and measured in-situ data (mean over 20 m under the free surface) Points C (1 -9) and M(1 -4) correspond to the in-situ measurements from COSTAS and Merlumed campaigns. PCB 153 in T 200 (ng/g. C) PCB 153 in T 60 (ng/g. C) PCB 153 in SPM (ng/g. C) PCB 153 in Diss. (pg/l) Measured in April Two size classes (X) of plankton are compared: Ø T 60 : 60µm<X<200µm ( « large » phytoplankton and microzooplankton); Ø T 200: 200µm<X<500µm (mesozooplankton).

Total PCB 153 in the Go. L Variation of mean concentrations (ng/l) due to input/output Rhone inflow Total concentration of PCB in Go. L Inflow/outflow by OBC

Total and non-living PCB 153 in the Go. L Variation of mean concentrations (ng/l) Total concentration of PCB in Go. L PCB in total dissolved form PCB in POM

Living PCB 153 in the Go. L Variation of mean concentrations (ng/l) HNF_PCB PHYL_PCB Predators and its preys : BAC -> HNF CIL-> CIL Copepod PHYL-> PHYL- Copepod HNF ->Copepod CIL_PCB BAC_C Winter + Rhone flooding BAC_C HNF_C Algal bloom PHYL_C Summer+ Rhone flooding HNF_C CIL_C

PCB 153 fluxes in g/d (zone IV, coast) during a flooding period of the Rhone River (2 months); preliminary results Example of the result interpretation. The fluxes depend on the chosen parameters and the period (flooding, bloom, etc. )

Conclusions Ø Estimated concentrations of PCBs in the different plankton size classes remain within same order of magnitude when compared with the limited field dataset of PCB determination in plankton in the Gulf of Lions Ø But lack of data to validate the model Ø The first results permit to study: Ø stocks of each species in the water column Ø fluxes between species, depending on time (seasons) and localization (coastal or wide area) Ø And the sensitivity of their variations to parameters and assumptions, according to biogeochemical and hydrodynamic conditions. Ø The model is complex (many variables) Ø but offers greater opportunities for investigations to see the effects of dynamics and biogeochemical processes, which are themselves validated and studied before.