Exploring Acidification Effects with a Coupled Biogeochemical and Size Spectra Model

Recent understanding that anthropogenic releases of CO₂ are altering the carbonate chemistry of the oceans has lead to concern that the physiological, biological and ecological impacts of ocean acidification could have significant ecosystem and societal impacts. To date the potential impacts of ocean acidification have predominantly been examined through experiments on the physiological performance of selected species under modified CO₂ environments. Whilst the direct effects of acidification occur at the molecular and cellular level, it is the expression of these impacts at the population and ecosystem level that are of societal concern. Therefore examining the potential effect of acidification on fisheries requires scaling from physiology to ecology.

Although the science-base to support ecological assessments of potential acidification impacts is still limited, given the extent and range of concerns that have been raised about potential impacts of acidification there is a need to provide timely advice and a balanced perspective on the possible impacts on marine fisheries. The potential impacts of acidification on fisheries are explored using an ecosystem model of the North Sea region of the North-East Atlantic; preliminary results are presented. This study applies a coupled hydrodynamic and lower trophic level biogeochemical model (ERSEM), linked to a higher trophic level community size-spectra model to examine the sensitivity of fisheries production to potential acidification effects such as alteration in biogeochemical recycling of nutrients, changes in plankton community structure and reductions in the productivity of calcifying benthic invertebrates.

Detailed projections of potential acidification effects require fuller understanding of the sensitivity of different biological processes across species. However examining the sensitivity of higher trophic level productivity to a range of potential acidification effects helps constrain the envelope of potential system responses whilst further experimental evidence is gathered. Furthermore modelling studies can usefully inform experimental research programmes by identifying critical sensitivities to potential acidification effects.