Palaeolimnological evidence of sensitivity of Lake Neusiedl (Austria) toward climate driven hydrological changes since the last “vanished-lake” stage

The palaeolimnological reconstruction of secular evolution respect to large (climate change) and local scale (land use, tourism environmental changes) of European Lakes with key socio-economical relevance, represented a major objective of the project EuLakes (European Lakes Under Environmental Stressors), launched in 2010 within the Central European Initiative. The project consortium comprised Lake Neusiedl, which is the lake with the largest surface area in Austria. The volume of Lake Neusiedl can considerably change over the years, in relation to the dynamic of the water balance driven by atmospheric precipitation and lake water evapotranspiration. The lake water budget affects physical (salinity and turbidity) and chemical lake properties and has important implications over the lake ecosystem. This contribution illustrates results of the multi-proxi palaeolimnological reconstruction of ecological changes occurred in Lake Neusiedl since the end of the last “vanished-lake” stage (1865-1871). Geochemical and biological proxies anticipated the increase in lake productivity over a period of about ten years in the 1950s. Sub-fossil diatoms species composition indicated a biological lake recovery in the late 1980s, and suggested a second increment in lake productivity since the late 1990s, likely in relation with increasing nitrogen input from agriculture. Ecological preferences of sub-fossil diatoms toward water salinity and moisture allowed to infer long-term changes in the lake solute level and thus to confirm the vulnerability of Lake Neusiedl toward climate-driven changes in the lake water balance. The semi-arid climate conditions of the catchment area on the one side, and pollution, biodiversity changes, and over-exploitation by agriculture and tourism on the other side can aggravate the lake fragility.