Ocean acidification in the outcome document of Rio+20

Ocean acidification is mentioned in paragraph 166 of the outcome document “The future we want” of the United Nations Conference on Sustainable Development (Rio+20).

Le fond des mers mis en boîte

On dirait un énorme aquarium de Plexiglas : c’est en fait un prototype de laboratoire sous-marin de deux mètres de long pour un mètre de large.  
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C’est la pierre de touche du programme européen Efoce, dédié au suivi à long terme de l’acidification des océans.

Isotope data improve the predictive capabilities of a marine biogeochemical model

Mesocosm experiments combined with biogeochemical modeling provide a powerful research tool to better understand marine ecosystem processes. Using an extended Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model, we investigated the added value of stable isotope tracer additions to constrain biogeochemical transformations within a mesocosm experiment that was designed to study ocean acidification effects on the marine ecosystem. Markov-Chain Monte-Carlo simulations revealed that even when isotope data were available for the majority of the components, not all parameters in the model could be constrained by calibration. However, when isotope tracer data were deliberately excluded from the calibration, the overparameterisation was even stronger. More specifically, it led to unconstrained fluxes through the zooplankton and detritus compartment, and different relative contributions of these two compartments to phytoplankton biomass loss produced equally plausible results. It is concluded that model uncertainty due to overparameterisation can be considerably reduced by explicitly resolving stable isotope dynamics. Therefore, this mesocosm experiment has benefitted substantially from isotope tracer additions to unravel carbon cycling under varying CO₂ regimes.