Development of a 3D coupled physical-biogeochemical model for the Marseille coastal area (NW Mediterranean Sea): what complexity is required in the coastal zone?

PLoS One. 2013 Dec 4;8(12):e80012. doi: 10.1371/journal.pone.0080012. eCollection 2013.


Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007-2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the biogeochemical model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the biogeochemical model.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Atmosphere
  • Carbon / chemistry
  • Chlorophyll / chemistry
  • Chlorophyll A
  • Ecosystem*
  • Environmental Monitoring*
  • France
  • Geologic Sediments / analysis*
  • Italy
  • Mediterranean Sea
  • Models, Statistical*
  • Nitrogen / chemistry
  • Phosphorus / chemistry
  • Rivers / chemistry
  • Seasons
  • Seawater / chemistry


  • Chlorophyll
  • Phosphorus
  • Carbon
  • Nitrogen
  • Chlorophyll A

Grant support

This work was supported by the PACA region (, IFREMER grant (, GIRAC ( and PNEC-EC2CO MASSILIA ( projects, sustained by the water agency (AERMC, and the PERSEUS European FP7 project ( The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.