Large-scale patterns of river inputs in southwestern Europe: seasonal and interannual variations and potential eutrophication effects at the coastal zone
|Author(s)||Romero Estela1, Garnier J1, Lassaletta Luis1, Billen Gilles1, Le Gendre Romain2, Riou Philippe2, Cugier Philippe3|
|Affiliation(s)||1 : Univ Paris 06, CNRS, UMR Sisyphe 7619, F-75005 Paris, France.
2 : IFREMER, Lab Environm & Ressources Normandie, F-14520 Port En Bessin, France.
3 : IFREMER, Lab Ecol Benth, Dept Dynam Environm Cotier, F-29280 Plouzane, France.
|Source||Biogeochemistry (0168-2563) (Springer), 2013-05 , Vol. 113 , N. 1-3 , P. 481-505|
|WOS© Times Cited||60|
|Keyword(s)||River inputs, Coastal zone, N:P:Si stoichiometry, Eutrophication, Seasonality, Europe|
|Abstract||We provide data on nutrient export for 28 rivers in southwestern Europe and analyze long-term changes in the context of anthropogenic pressures and regulation policies. Special attention is given to seasonal variations, because the integrated annual values that are usually provided do not allow us to establish comparisons with seasonal phytoplankton dynamics. The eutrophication risk associated with river inputs is addressed by means of an indicator (Index of Coastal Eutrophication Potential, ICEP, Billen and Garnier, Mar Chem 106:148–160, 2007). An overview of the temporal evolution and the intra-annual variability of the ICEP is discussed for specific rivers and integrated coastal regions. The annual dynamics of the eutrophication indicator is analyzed to delimit those periods when the risk of eutrophication is particularly high. The trends in nutrient fluxes and coastal phytoplankton are compared by means of a case study (Seine Bay). The decrease in phosphorus matches a general decrease in phytoplankton biomass in the summer. However, sustained high values of nitrogen still foster the emergence of harmful algal blooms, and we found an increase in the summer abundance of dinoflagellates. The abatement of phosphorus alone is not enough to shortcut harmful blooms and toxic outbreaks in the Seine Bay. A reduction in nitrogen inputs may be necessary to effectively minimize eutrophication problems.|