Erschienen in: Hydrobiologia ; 824 (2018), 1. - S. 291-321 https://dx.doi.org/10.1007/s10750-018-3677-x Large and deep perialpine lakes: a paleolimnological perspective for the advance of ecosystem science Monica Tolotti . Nathalie Dubois . Manuela Milan . Marie-Elodie Perga . Dietmar Straile . Andrea Lami 2 Abstract The present paper aims at reviewing with zmax C 100 m and lake area C 10 km , and on 4 general knowledge of large European perialpine lakes shallower perialpine lakes representing hotspots of as provided by sediment studies, and at outlining the extensive neo- and paleo-limnological research. By contribution, from several lines of evidence, of pinpointing temporal and spatial differences in pale- modern paleolimnology in both interpreting past lake olimnological studies conducted in the Alpine coun- ecological evolution and forecasting lake responses to tries, the review identifies knowledge gaps in the future human impacts. A literature survey mainly perialpine area, and shows how sediment-based based on papers published in international journals reconstructions represent a powerful tool, in mutual indexed on ISI-Wos and Scopus from 1975 to April support with limnological surveys, to help predicting 2017 has been conducted on the 20 perialpine lakes future scenarios through the ‘‘past-forward’’ principle, which consists in reconstructing past lake responses to conditions comparable to those to come. The most Guest editors: Nico Salmaso, Orlane Anneville, Dietmar Straile & Pierluigi Viaroli / Large and deep perialpine lakes: recent methodological developments of sediment ecological functions and resource management M. Tolotti (&) M.-E. Perga Department of Sustainable Agro-ecosystems and Institute of Earth Surface Dynamics, Geopolis, University Bioresources, Research and Innovation Centre (CRI), of Lausanne, Quartier UNIL-Mouline, 1015 Lausanne, Fondazione Edmund Mach (FEM), Via Mach 1, Switzerland 38010 S. Michele all’Adige, Italy e-mail: [email protected] M.-E. Perga CARRTEL, INRA-University Savoie-Mont Blanc, N. Dubois 74203 Thonon-les-bains Cedex, France Geological Institute, Department of Earth Sciences, ETH Zu¨rich, Sonneggstrasse 5, 8092 Zu¨rich, Switzerland A. Lami Istituto per lo Studio degli Ecosistemi, ISE-CNR, Largo N. Dubois V. Tonolli 50, 28922 Verbania, Italy Department of Surface Waters Research and Management, Eawag, U¨ berlandstrasse 133, 8600 Du¨bendorf, Switzerland M. Milan Á D. Straile Limnological Institute, University of Konstanz, Mainaustrasse 252, 78464 Konstanz, Germany Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-2-1sugv88nloavf2 292 studies show the potential to cope with the increasing population still represents a major human threat for ecosystem variability induced by climate change, and several LDPLs. Perialpine lakes are still exposed to to produce innovative and crucial information for point-source pollution (e.g. from productive activi- tuning future management and sustainable use of ties), but airborne NOx (Rogora et al., 2006), persistent Alpine waters. organic pollutants (POPs) from agriculture, urban and industrial areas (Guzzella et al., 2018), as well as Keywords Perialpine lakes Á Lake sediments Á ‘‘new’’ pollutants, such as microplastics (Faure et al., Human impact Á Eutrophication Á Paleoclimate Á 2012; Imhof et al., 2013) and drugs inducing antibiotic Global change resistance (Di Cesare et al., 2015), currently represent the most widespread contamination threat. Alien species, which easily spread also in relation to tourist transfer (Gherardi et al., 2008), are becoming a crucial Introduction issue for the conservation of biodiversity and ecosys- tem services of LDPLs. According to the classification by Timms (1992), large Nevertheless, the sensitivity of LDPLs to climate and deep perialpine lakes (LDPLs) are distinguished change currently represents a hot issue due to the tight from the other two major categories of alpine lakes relation existing between LDPL physiography, their (i.e. high alpine and alpine) based on their piedmont peculiar thermal dynamics (i.e. holomixs with com- position and their tectonic-glacial origin, which is plete thermal circulation only after cold and/or windy related to the past dynamics of large Alpine glaciers winters, Ambrosetti et al., 2003) and major atmo- occupying ancient and deep canyon-valleys (Bini spheric circulations (Salmaso et al., 2014). These et al., 1978). factors together represent key drivers of transport LDPLs represent a key water resource for the processes in water and sediments, and of water densely populated Alpine region. For example, the chemistry, nutrient availability, water transparency five largest Italian subalpine lakes represent * 80% and biological dynamics of LDPLs (e.g. Manca et al., of the total Italian freshwater resources (Salmaso & 2000; Straile et al., 2003; Jankowski et al., 2006; Mosello, 2010), while L. Geneva and L. Constance George, 2010; D’Alelio et al., 2011). Water temper- provide drinking water for [ 800,000, respec- ature is increasing in many lakes of the northern tively * 5 million people (CIPEL, Commission hemisphere, including perialpine lakes (O’Reilly internationale pour la protection des eaux du Le´man, et al., 2015), but the evidence that global warming is www.cipel.org, Petri, 2006). LDPLs are extensively more pronounced in mountain regions (Gobiet et al., used also for irrigation and industry, and represent key 2014) is of particular concern, as the LDPL catch- regional resources for tourism, while waters within the ments extend to the glacial Alpine ranges. The LDPL catchments are intensively used for hydropower progressive Alpine deglaciation and the changing production since the 1930s (Wu¨est et al., 2007; Sal- precipitation pattern predicted for the twenty first maso & Mosello, 2010). Concern about the sustain- century (Beniston, 2006; IPCC, 2013; Radic´ et al., ability of these ecosystem services among 2014) have the potential to strongly affect the stakeholders and end-users stimulated the launching of hydrological regime of perialpine lake catchments, long term monitoring programmes of some key and to produce negative ecological and socio-eco- LDPLs already in the 1950/1960s. Intensification of nomic effects related to water scarcity. the research activity at local and regional level took The present context of multiple stressors and place at some sites in the late 1990s (e.g. within the superimposed global warming is challenging the European Long Term Ecological Research Network, sustainable management of LDPLs, especially in LTER, http://www.lter-europe.net), with the objective connection to the insufficient knowledge of the of assessing future vulnerability of perialpine lakes complex interactions between local human impacts and outlining common developing trends within the and climate variability, and of the related lake modern context of multiple and trans-boundary human ecological responses. On the other hand, the present impacts. The results of these studies pinpointed that environmental and socio-economic context of LDPLs nutrient enrichment related to resident and tourist makes the need for better capacity to predict future 293 lake development increasingly urgent. According to paleolimnological research to the knowledge of LDPL the EU Water Framework Directive (European Com- responses to human stressors at secular-scale, and to mission, 2000), current lake ecological quality and the assessment of perialpine lake sensitivity to present restoration targets have to be defined as the degree of and future human impacts. By pinpointing spatial and deviation from good pre-impact quality, i.e. from temporal differences in paleolimnological research ecological reference conditions (European Commis- conducted in the different Alpine countries, this work sion, 2003), which characterize less or not impacted has the additional objective of identifying knowledge reference lakes or past periods in the development of a gaps in the study of lacustrine sediment in the certain lake. However, due to the variety and spatial perialpine area, and of exploring the potential of distribution of human perturbations on lacustrine modern methodological approaches to answer open ecosystems, reference lakes are in reality rare or basic and applied limnological research questions. scarcely representative for the majority of lake According to geography and bedrock geology five categories (Buraschi et al., 2005). Furthermore, high major sub-groups of LDPLs are recognized (Fig. 1): quality long term limnological data are available only (1) Savoyan lakes (F) located on calcareous bedrock for a few key perialpine lakes, such as for Lakes and with waters of middle hardness, (2) lakes of the Lucerne and Constance since the early twentieth Swiss Plateau (CH, D, A) receiving waters form the century (Wolff, 1966; Grim, 1968), L. Geneva since crystalline mountain ranges of the Central Alps, (3) 1957 (Monod et al., 1984), Lakes Maggiore and lakes of the Southern Alps (I, CH) mainly located at Lugano since 1973 (http://www.cipais.org/index.asp). lower altitude (average = 245 m a.s.l., Table 1)in Smaller lakes usually received attention only after calcareous regions and with watershed basins extend- symptoms of cultural eutrophication became evident ing in the crystalline Central Alps, (4) Bavarian in the 1960s–1970s (e.g. Alefs & Mu¨ller, 1999; Gar- (D) and (5) Salzkammergut (A) lakes located at ibaldi et al., 1999). Although the decadal-scale data altitudes