Livestock effects on the lakes of Aigüestortes and Sant Maurici Lake National Park: nitrogen inputs and eutrophication risk
High mountain landscapes do not escape the effects of the increased nitrogen atmospheric deposition caused by human activities during the last few decades. In addition to this, livestock grazing on high mountain natural pastures during the summer might modify the quantity and composition of nutrient load entering lakes, thus affecting production rates in these ecosystems. The present proposal seeks to evaluate the effects of livestock on lakes in the Aigüestortes and Sant Maurici Lake National Park, and to assess the eutrophication risk posed by livestock as it interacts, perhaps synergistically, with increased nitrogen deposition rates. Our proposal suggests addressing these questions at three distinct spatial and temporal scales. At the scale of the lakescape, we propose to build statistical models linking livestock pressure, atmospheric deposition, and lake and catchment characteristics with in-lake nutrient concentrations and stoichiometry. At the lake and catchment scale during the entire ice-free season, we seek to analyse in greater detail the effects on the biomass, composition, and activity of plankton, including Archaea and Bacteria. Finally, at the individual lake scale, we propose to analyse the local effect of livestock on the composition and biomass of algal and macrophyte communities, and on microbial activity.