(First) Paleo-ecological recostruction of the last two centuries evolution of Lake Garda

Lake Garda is one of the four large Central European lakes included in the EuLakes Project (Reg. Nr. 2CE243P3), within the Central European Initiative. The main aims of this project are to evaluate the lake vulnerability against specific human stressors (e.g. nutrients, hydroelectrical exploitation) in a climate change scenario, and to promote sustainable lake management. Sediment studies are being used to determine the lake reference conditions before stronger human impact. Lake Garda is the largest Italian lake. The deep basin (350 m) is little impacted by human activities and is suitable for reconstructions of long term environmental variability, including climate change and its effect on lake ecology. In contrast, the shallow basin (81 m) is strongly affected by tourism and intensive agriculture, and is therefore more suitable for studies on lake eutrophication. This contribution presents results of the analysis carried out on one short sediment core (56 cm) collected from the deepest point of Lake. The focus is on changes in sub-fossil diatom assemblages since the early 20th century. The core presents two discontinuities. The first one in early 1960, with an increase of Fragilariaceae in spite of centric taxa, as result of nutrient enrichment and climate change. The second one in mid 1940s, with a decrease in benthic taxa, which may be related with the intensive hydroelectrical exploitation of the catchment area. A preliminar diatom based reconstruction of lake TP concentration over the last 200 years match with recent limnological data.