Created 02/06/2016 Updated 25/02/2017

Carbon Cycle in the Rhône estuary and Gulf of Lions (CARBORHONE)

The spatial variability in air-sea CO2 fluxes is large from one coastal ecosystem to the other and it was recently proposed to classify continental shelves as sinks and near-shore ecosystems as sources  of  atmospheric  CO2.  However,  the  latest  estimates  of  air-sea  CO2  fluxes  in  coastal ecosystems  are  subject  to  large  uncertainty.  At  present,  the  lack  of  sufficient  data  is  the  major  limitation  in  the  quantification  of  the  spatial  and  temporal  variability  of  these  CO2 fluxes in coastal environments. This lack of data is even more relevant in coastal ecosystems impacted  by  estuarine  plumes.
While  there  is  an  emerging  agreement  on  the  role  of  inner  estuaries  as  source  of  CO2 to  the  atmosphere,  estuarine  plumes  (e.g.  outer  estuaries)  can  either act  as  sources  or  as  sinks  for  atmospheric  CO2. To  accurately  constrain  the  present impact  of  estuarine  plumes  in  global  air-sea  CO2 fluxes,  additional  investigations  must  be carried out in a greater diversity of ecosystems.
The air-sea CO2 fluxes in Mediterranean coastal ecosystems impacted by estuarine inputs have been particularly poorly  investigated.
The   Gulf   of   Lions   is   a   coastal   ecosystem considerably  impacted  by  freshwaters  inputs  from  the  largest  estuary  surrounding  the Mediterranean  Sea  namely  the  Rhône.  In  the  framework  of  the  MERMEX -CARBORHONE project,  we  investigated  the  processes  controlling  the  air-sea  CO2 fluxes  from  the  inner estuary to the estuarine plume located  within the 1500 m isobath of the Gulf of Lions. 


© Yann Bozec / SBR / CNRS

Our approach relied on 4 seasonal cruises carried out in 2011 and 2012.

- CARBORHONE 1 & 2 cruises: 2011

-CARBORHONE 3 & 4 cruises: 22nd February- 3rd March 2012 & 20th - 28th July 2012 Gulf of Lions, Western Mediterranean Sea.

Figure 1 : Chlorophyll a surface concentrations (satellite image in november 2011 during CARBORHONE 2 cruise.


© Yann Bozec / SBR / CNRS

Data collected during the cruises :

-SSS, SST (SeaBird SBE21) to determine the Rhone plume surface.

-sea surface pCO2, DO

-31 CTD (Sea Bird SBE32) casts with seawater sampling for biogeochemical parameters within the whole Gulf of Lions

Cruises are scheduled during different seasons (spring, summer, fall, beginning and end of winter) so as to study different discharges of the Rhone river.

All those data are to be combined with satellite data (T, Chl a,…) (Figure 1) in order to monitor the process controlling air-sea CO2 fluxes for each season.

Figure 2 : Onboard Téhtys



It also gets logistical support from CNFC, DT-INSU and IFREMER/Génavir.



French collaborators

AD2M-Chimie Marine (CNRS/UPMC, Station biologique de Roscoff), LOCEAN (CNRS/UPMC, Paris), LSCE (CNRS/UPMC, Gif/Yvette).