Biogeochemical cycling in estuaries

Situated at the transition between freshwater and marine environments, estuaries are key components of the land–ocean aquatic continuum. They act as strong nutrient and carbon filters and are relevant contributors to the atmospheric CO2 budget. Along the estuarine gradient, oceanic and terrestrial carbon and nutrient inputs are modified by biogeochemical processes, buried in sediments, incorporated into biomineralized structures or, in the case of gaseous species such as CO2, exchanged with the atmosphere.

However, the quantitative significance of the estuarine bioreactor as a regulator of land–ocean carbon and nutrient fluxes or global atmospheric CO2 concentrations remains poorly constrained. This limited quantitative understanding mainly results from the inherent spatial and temporal variability of the estuarine environment that is difficult to resolve on the basis of observations alone.

We develop and use both local and global models of alluvial estuaries to elucidate nutrient and carbon cycling in estuaries, assess their significance as a regulator of land–ocean carbon and nutrient fluxes, as well as their role in regional CO2 budgets.

Relevant project(s): RECAP

People involved: Sandra Arndt, Goulven Laruelle, Ronny Lauerwald, Pierre Regnier

Key publications:

  • Regnier, P., Arndt, S., Goosens, N., Laruelle, G., Lauerwald, R., and Hartmann, J. 2013 Quantification of estuarine biogeochemical dynamics: From the local to the global scale. Marine Chemistry, 19, 591-626.
  • Volta, C., Arndt, S., Laruelle, G., Regnier, P., Savenije, H., 2014. C-GEM: A new cost efficient biogeochemical model for estuaries and its application to a funnel-shaped estuary., Geoscientific Model Development, 7, 1271-1295.
  • Laruelle, G. G., Goossens, N., Arndt, S., Cai, W.-J and Regnier, P., Air-water CO2 evasion from U.S. East Coast estuaries, Biogeosciences, 14, 2441.
  • Arndt, S., Regnier, P., and Vanderborght, J.-P., 2009. Seasonally-resolved nutrient export fluxes and filtering capacities in a macrotidal estuary, Journal of Marine Systems, 78, 42-58.