Today’s stage takes us out of the Alps along the valley of the Durance to Salon-de-Provence. The Durance, which rises in the Alps near Briançon, naturally flows into the Rhône near Avignon, but in 1966, the Canal de l’EDF was constructed to divert the waters of the Durance south, past Salon-de-Provence and through a hydroelectric station into the Étang de Berre, a coastal lagoon near Marseille.
Diverting so much freshwater from the Durance into the lagoon caused dramatic changes in its ecosystem (Bernard et al. 2005). The salinity of the lagoon declined, and the water stratified with the less dense freshwater sitting on top. Nutrient inputs from the canal led to eutrophication as microbes excited by the higher nutrient levels eat up all the oxygen in the pond. The sediment inputs from the canal that you can see in the SPOT image above reduced the amount of light that makes it to the bottom. All of these changes stressed the seagrass communities of the lagoon. Reductions in the freshwater discharge through the power station have improved the water quality in the lagoon, but the seagrass has yet to return fully (Bernard et al. 2007).
What a win by Edvald Boasson Hagen, finally getting that elusive victory for Dimension Data! That move on the roundabout was incredible to watch.
- Bernard et al. (2005) Recovery of the seagrass Zostera marina in a disturbed Mediterranean lagoon (Etang de Berre, Bouches-de-Rhône, Southern France). Hydrobiologia. http://dx.doi.org/10.1007/s10750-004-3080-7
- Bernard et al. (2007) Long term changes in Zostera meadows in the Berre lagoon (Provence, Mediterranean Sea). Estuarine, Coastal and Shelf Science. http://dx.doi.org/10.1016/j.ecss.2007.03.003