13 Nov. 2012 - Vincent Berthon

Using fossil diatoms and rotifer resting eggs to reconstruct past anthropogenic impacts on large lakes

Presenta: *Vincent Berthon
Collaboratori: Benjamin Alric*, Aldo Marchetto**, Emmanuelle Dormia*, Frédéric Rimet*, Marina Manca**, Marie-Elodie Perga*
* INRA – Thonon Las Bains, France; ** CNR-ISE Verbania, Italia

During the XX century, lacustrine ecosystems have undergone deep changes due to increased human activities. Although significant restoration efforts have been undertaken since the 1980es, their efficiency can be limited. For instance, although phosphorous concentrations of Lake Geneva have been cut by a factor of 10 in the last 30 years (for a total cost of four billlions euros), the algal biomass and the primary production remain as high as during the eutrophication maximum, even if water transparency increased. So, the counter-intuitive response of lakes to restoration measures emphasizes that although phosphorous concentration is a major driver of phytoplankton, there is a need to consider the interaction with other environmental drivers, such as climate or top-down controls. Our objective is to understand such scenario by investigating high-resolution paleolimnological data focusing on the planktonic communities (diatoms and rotifers) of three lakes (Geneva, Annecy and Bourget), disentangling the effect of changes in nutrient concentrations, fisheries management practices and climate change.

click to download notice of seminar