Littérature scientifique sur le sujet « European perialpine lakes »

Abstract The study of invasive species often focuses on regions of recent introduction rather than native habitats. Understanding an invasive species in its natural environment, however, can provide important insights regarding the long-term outcome of invasions. In this study we investigated the diet of the invasive spiny water flea, Bythotrephes longimanus, in two Austrian perialpine lakes, where it is native. The gut contents of wild-caught Bythotrephes individuals were estimated by quantitative polymerase chain reaction, targeting species-specific fragments of the barcoding region of the cytochrome c oxidase I gene of potential prey. The observed prey spectrum of Bythotrephes in the study lakes consisted primarily of Eudiaptomus gracilis and Diaphanosoma brachyurum. The Daphnia longispina complex, Leptodora kindtii and Mesocyclops leuckarti also contributed to the diet. Results indicate that Bythotrephes is a generalist feeder with a preference for epilimnetic prey.

In this paper we review a significant sample of the modelling studies carried out on medium-to-large deep European perialpine lakes (MLDEPLs). The reviewed bibliographic corpus was obtained querying Elsevier’s Scopus® database with a tailored search string on 8 January 2021. Results were filtered, accepting only journal papers written in English dealing with natural lakes having surface area > 10 km2. A list of 75 works was obtained, published between 1986 and 2021. Most studies have been carried out on Swiss lakes (44 out of 75 papers), Lake Geneva being the most investigated environment. A significant positive correlation was found between lake surface area and volume and the number of dedicated papers, suggesting that scientific attention is higher for environments characterised by large dimensions and relevant socio-economic interests. Both the number of papers and their citation count have experienced an exponential growth in time, pointing to a rising interest in quantitative modelling applications, but also to the increasing availability and ease of use of numerical modelling tools. Among the 75 selected papers, 55 employ a hydrodynamic driver, used alone or coupled with an ecological module, while the remnant 20 works adopt an ecological-only model. Among the papers employing hydrodynamic models, the use of three-dimensional (3D) drivers is surprisingly slightly more frequent (28 papers) than that of one-dimensional (1D) ones (26 papers), with most 3D applications having been published in the last 2011-2020 decade (24 papers). This reflects the interest on the hydrodynamic processes leading to the observed spatial heterogeneities in the biochemical properties of the MLDEPLs. However, coupling of ecological modules with 3D hydrodynamic drivers, to directly simulate these phenomena, is still restricted (2 papers) compared to that of 1D hydrodynamic drivers (8 papers), due to calibration and computational difficulties, which could be strongly reduced by future research achievements. Nevertheless, 1D models allow performing long-term prognoses considering multiple climate change and watershed management scenarios, due to their much smaller computational burden. The largest group of works dealing with ecological-only models (6 papers) is dedicated to applications of phosphorus budget models, which can above all be used to forecast variations in lake productivity in response to changes in the availability of the limiting nutrient. Graphical abstract

Water management is facing a growing number of challenges in many river basins worldwide, as the equal distribution of the available water resources is increasingly influenced by several, uncertain climatic and anthropic pressures. Within the current and projected water scarcity and drought scenario, such issue represents even a greater challenge in those basins that have been massively regulated in the XX century, as water managers are asked to find balanced policies to stay ahead with multiple, interdependent and ever-increasing water-related requirements. In this context, water conflict has become a recurring problem, with the freshwater ecosystems becoming the sole providers of unbearable human water needs and experiencing a severe alteration of their natural renewability and ecological integrity. In fact, the concern of sustaining the freshwater ecosystems has evolved throughout the years, coming to the fore since the 1990s under the concept of "ecosystem services", defined as the multiple benefits that people obtain from ecosystems. With a high number of challenges still ahead for implementing such paradigm in real-world water management practices, few investigations inspect the long-term evolution of highly regulated basins, being vulnerable freshwater systems characterized by a profusion of ecosystem services in a context of complex management policies and changing anthropic and climatic pressures. We focus our attention on the highly interconnected Garda-Mincio system (Northern Italy), further broadening the results to the regulated basins of the European perialpine region. First, to examine the modification of the freshwater systems from their pristine to their regulated conditions, we carried out an extensive collection of daily hydro-meteorological data by consulting public online sources as well as digitizing historical data contained in hand-written documents. The resulting database, which represents a valuable source of long-term daily hydro-meteorological data for the Garda-Mincio system, additionally underscored the complexity of constructing and maintaining a consistent and up-to-date database within an inter-regional context. The collected data were then adopted to investigate the climatic and anthropogenic drivers that have progressively influenced water availability, the provision of the changing water demands and the trade-offs with the existing water ecosystem services over the last two centuries. Statistical analyses were performed to outline the evolution of the annual and seasonal trends of Lake Garda water levels and outflows over the period 1888-2020, discussing the role of the Salionze Dam operational rules (completed in 1951) as well as the influence of the main water needs of the downstream Mincio River basin (i.e. hydropower production, irrigation and fluvial ecosystem sustenance). The role of hydro-meteorological factors was assessed by implementing a water balance model for Lake Garda, the largest lake in Italy, over the period 1928-2020, performing uncertainty and sensitivity analyses on specific water balance components (i.e. over-lake evaporation and basin evapotranspiration). We then focus our analyses on the management of the hydraulic infrastructures that regulate the first and highly water-stressed stretch of the Mincio River downstream Lake Garda, i.e. the Salionze Dam and the Pozzolo-Marenghello infrastructures, where both high and low flow conditions reveal the inability of the current operational rules to support the new variety of water abstractions while maintaining appropriate environmental flow conditions and flood protection. These analyses were carried out through in-situ measurements and numerical simulations, updating the aging rating curves of the existing hydraulic infrastructures. Drawing on the Garda-Mincio system, we inspected the evolution of the freshwater regimes within the European perialpine lakes framework, discussing the outcomes to describe which common factors drove management policies in the area. Eventually, we discuss our outcomes recommending future sustainable and adaptive water management policies in the area.

Projet Lac was a large project conducted by Eawag and the University of Bern to quantitatively survey, for the first time, whole-lake fish communities in the large and deep lakes in and around the European Alps using multiple, standardised sampling methods. Starting in 2010, in total 35 lakes were investigated across Switzerland, Italy, France, Germany and Austria, with more than 106 fish species recorded. This report brings together key findings, compares fish communities among lakes, investigates their relationship to environmental parameters, and provides an overview of drivers of biodiversity and community structure in this important ecosystem.