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FS 26.112

Mountain lakes and ponds under human pressure and global threats

Session status: Accepted

Content last updated: 2026-04-16 00:06:26

Online available since: 2025-12-17 14:58:40

Details

Full Title
Sentinels at risk: monitoring, conservation, and management challenges for mountain lakes and ponds under human pressures and global change
Scheduled
TBA
TBA
Chair
Rogora, Michela
Co-chair(s)
Tolotti, Monica; Sommaruga, Ruben; Tiberti, Rocco; and Brighenti, Stefano
Thematic Focus
Climate, Cryo- & Hydrosphere, Ecosystems, Monitoring, Tourism
Keywords
Mountain freshwater, Biodiversity, Pollutants, Climate change, Overtourism

Abstract/Description

High mountain lakes and ponds provide essential ecosystem services and have a high conservation and aesthetic value. Due to their specific features, they may host specialized communities with still partly unknown ecology and biodiversity. They are also particularly sensitive to environmental stressors and are considered sentinels of global change. Mountain freshwaters are also extremely sensitive to climate change, being affected by increasing temperature, changing precipitation regime, and cryosphere thawing, with related impact on water quality and habitat conditions.

Although often considered pristine systems, lakes and ponds in high-altitude regions are threatened by both local and global anthropogenic pressures, which in many cases can compromise their ecological integrity, affect water quality and exacerbate conflict of interest for their use. Among local pressures, the increasing touristic pressure in many mountain areas represents an additional threat to mountain lakes, adding to the pervasive presence of fish introductions and livestock grazing: unsustainable recreational use may affect trophic status and ecological functioning of lakes by increasing nutrient loads and the level of emerging pollutants, whose toxic effects are still poorly understood. The potential or already evident effects of human pressure are even more relevant for freshwater systems not included in protected areas or not subject to any environmental legislation.

The combined effects of several pressures, including overtourism and water exploitation for different uses, need to be assessed through proper indicators. Research and monitoring programs, as well as restoration and conservation plans, should consider the interaction of different pressures and combine various approaches, from in-situ data collection, to remote sensing and modelling. Also, citizen science and other initiatives of participatory science may contribute to better knowledge and to raise awareness about the importance and vulnerability of freshwater ecosystems.

This session welcomes contribution from different disciplines and perspectives, possibly combining interdisciplinary approaches and focusing on the emerging threats to mountain lakes and ponds due to the increasing and changing nature of human activities in mountain areas. The objective is to share results and/or approaches and stimulate the discussion.

Registered Abstracts

ID: 3.10

The BioAlpine project: bridging the gap between global changes, biodiversity structure, and alterations in ecosystem functioning and services in high-altitude lakes of the Alps.

Flavia Dory
Ben Salem, Asma; Bertrand, Céline; Boudenne, Jean-Luc; Coulomb, Bruno; Demelas, Carine; Franquet, Evelyne; Fruchet, Alexis; Hohener, Patrick; Lepoupon, Christophe; Martino, Christian; Misson, Benjamin; Mounier, Stéphane; Oursel, Benjamin; Pichard, Baptiste; Prudent, Pascale; Ravier, Sylvain; Robert Peillart, Fabien; Vassalo, Laurent; Cavalli, Laurent

Abstract/Description

High-altitude lakes have been identified as sentinels of global change, acting as early warning systems. Their characteristics make them extremely vulnerable to environmental changes driven by human activity, and, in this sense, they constitute good models for detecting and analyzing the effects of global changes. Although they are generally perceived as pristine, alpine lakes are threatened by air pollution and are highly vulnerable to climate change. The BioAlpine project aims to better understand the links between global changes, biodiversity structure, and alterations in ecosystem functioning and services in high-altitude lakes of the Alps. In particular, the project aims to know: (i) if there are differences in the food web’s structure and in the transfer of organic matter among alpine lakes, especially in relation to phytoplankton composition; (ii) if there are variations of atmospheric contaminants (N, P, metallic pollutants, organic pollutants) in lakes with different characteristics (location, depth, watershed size); (iii) if there is a link between the food web structure and the bioaccumulation of pollutants in higher trophic levels (fishes). In total, eight high-altitude lakes with different characteristics, distributed along a longitudinal gradient, will be sampled in 2025 and 2026 in the French Alps. Sampling will be carried out over three campaigns, winter, spring, and late summer, to provide a complete description of lake functioning. Here, we present the first results of the project, focusing on phytoplankton community structure and composition.

ID: 3.15

The importance of climate on mountain Lake Tovel, a long-term and short-term perspective

Ulrike Obertegger
Obertegger, Ulrike; Corradini, Stefano; Pindo, Massimo; Cerasino, Leonardo

Abstract/Description

Lake Tovel (1,177 m above sea level; area: 0.4 km²; maximum depth: 39 m) is an Italian long‐term ecological research site in the Brenta-Adamello Natural park and is monthly sampled from 1995 onwards. Its high protection status and long-term data make it an excellent sentinel of climate change. At Tovel, classical limnology is combined with high-frequency sensors and environmental DNA. This contribution shows how a long-time meromictic lake changed to an oxygenated hypolimnion because of climate change and which repercussions this had on plankton. The comparison of the fungal community assessed by eDNA further outlined the impact of a dry versus a wet year on community dynamics. Lake Tovel is an excellent example of the intertwined relationships of climate change and plankton.

ID: 3.56

From snowmaking to ecosystems: Zooplankton diversity and environmental drivers in mountain reservoirs of the Eastern Alps

Barbara Tartarotti
Rastl, Nikolai; Sommer, Fabian

Abstract/Description

Artificial snow production is becoming increasingly essential for ski operations under climate change, leading to the construction of mountain reservoirs across the Alps. While these reservoirs can alter mountain ecosystems and landscape structure, they also provide novel habitats for aquatic organisms such as zooplankton. In addition to the inherent harshness of alpine environments, organisms in these systems must withstand fluctuations in water levels and frequent artificial mixing. Here, we surveyed zooplankton and recorded physicochemical variables in eleven mountain reservoirs in the Eastern Alps to document species occurrence, assess similarity to nearby natural alpine lakes, and identify environmental correlations. Zooplankton were present in all mountain reservoirs (22 taxa in total; 1-11 taxa per reservoir; mean 7 taxa). The species composition broadly resembled that of adjacent natural lakes, and nearby reservoirs tended to be compositionally similar. Zooplankton abundances varied widely (summer: 0.09-168.74 Ind L⁻¹; autumn: 0.04-1092.78 Ind L⁻¹) and were significantly related to environmental variables including elevation, dissolved organic carbon, food availability (chlorophyll a), pH, K⁺, total phosphorus, and Ca²⁺. Rotifers dominated numerically, whereas crustaceans dominated biomass. Overall, local environmental conditions had a stronger effect than regional factors on these rapidly changing systems. Despite their artificial origin, mountain reservoirs support zooplankton communities that are comparable to those in natural lakes, thus improving our understanding of the distribution of zooplankton in remote mountain regions.

ID: 3.55

Anthropogenic footprint on high mountain lakes: a case study form the European Long-Term Ecological Research network (eLTER)

Michela Rogora
Kamburska, Lyudmila; Cesarini, Giulia; Galafassi, Silvia; Piscia, Roberta

Abstract/Description

Lakes Paione Inferiore (PAI) and Paione Superiore (PAS) are two glacial lakes located in the Western Alps, Piedmont Region, Italy, at 2002 and 2269 m a.s.l. respectively. They have been extensively studied since the 1980s within EU-funded research projects on transboundary air pollution and climate change effects on mountain lake ecosystems. Thanks to the pluriannual data available, the lakes have been included in the European Long Term Ecological Research (eLTER) network. Although close each other, and part of a system of three cascading lakes, PAS and PAI differ in their main physico-chemical characteristics, in relation to morphological, geographical and catchment cover features. The two lakes are also subject to different levels of anthropogenic pressure, as the lower lake is more easily accessible, lies along a hiking route connecting other lakes within the valley, and consequently attracts more visitors. Furthermore, PAI has been subjected to repeated fish stocking during the last 40 years, while PAS is relatively more remote and appears to be less impacted. This difference has been confirmed by a recent preliminary investigation into the presence of microplastics (MPs) in the two lakes and their final outlet: MPs abundance and size increased progressively from the upper lake to the outlet, with local activities likely playing a more substantial role in MPs occurrence in PAI and its outlet. Fibers were the dominant type of MPs and the polymers detected were among the most frequently found in remote ecosystems, suggesting outdoor clothing and equipment as the main source. The other anthropogenic pressure, fish stocking in PAI, appears to alter trophic structure and ecosystem functioning, resulting in substantially higher zooplankton abundance and diversity in PAS than in PAI. These examples demonstrate how human activities exert a major effect on mountain lake ecosystems, affecting water quality and biodiversity, and often interacting with other pressures such as long-range atmospheric pollutants and climate change. Proper management of touristic fluxes and activities potentially affecting mountain lakes (hiking, fishing, picnicking) is needed to protect these fragile ecosystems, also through educational and participatory science initiatives.

ID: 3.68

Mountain lakes vulnerability to warming in the face of climate change

Isabel Herr
Perga, Marie-Elodie; Bouffard, Damien

Abstract/Description

Mountain lakes are often described as sentinels of climate change, a designation earned through their dual high exposure and sensitivity to changing climatic conditions. Although air temperatures in the European Alps have risen at roughly twice the global average, long-term warming rates in mountain lakes often remain muted and diverge from trends observed in lowland or ice-free systems. Increasing evidence suggests that this discrepancy is driven by cryospheric controls, particularly snowpack, late-lying snow, and glacial melt. Snowmelt inflows can delay spring warming, disrupt stratification, and reduce summer heat accumulation by advecting cold water through lakes and shortening water residence times. These processes are captured in a three-phase conceptual framework, that we proposed in a previous study, in which alpine lake heat budgets transition seasonally between ice-dominated, watershed-dominated, and atmosphere-dominated regimes. From a detailed multi-year heat budget study of a mountain lake, we showed that the magnitude of water warming during the open-water season depends on the length of the watershed-dominated phase.

Although mechanistically interesting, the previously applied heat budget approach has limited generalizability, as it requires detailed hydrological measurements that are rarely available for remote alpine lakes. Here, we aim to test whether the three-phase conceptual model can be used to assess alpine lakes’ vulnerability to warming under climate change in a data-limited context. We analyse the heat budgets of 23 alpine lakes in the Lacs Sentinelles network, in the French Alps. Using differences between modeled vertical heat fluxes and observed changes in lake heat content, we infer the timing and duration of watershed-dominated periods without direct discharge measurements. We then assess how lake and watershed morphology govern the length of the watershed-dominated phase and the sensitivity to snowpack conditions, deriving a vulnerability map for alpine lakes’ vulnerability to warming.

ID: 3.81

FishMe Management Toolbox: Knowledge and information on fish removal in mountain lakes

Davnah Urbach
Cogălniceanu, Dan; Stănescu, Florina; Tănase, Teodora L.; Vlad, Sabina E.; Snethlage, Mark; Ranipeta, Ajay

Abstract/Description

Together with increasing pollution and the simultaneous effects of climate and land-use change, including the expansion of hydropower infrastructures, the introduction of alien fish in mountain freshwater ecosystems has become an increasing concern over the last decades. Whereas a considerable amount of literature exists on the ecological consequences of these introductions, less is known about how to manage or eradicate introduced fishes and the existing information is scattered. Here, we present the “FishMe Toolbox”, a digital, open access infrastructure for the collection, access, and sharing of technical and non-technical information on needs and options for fish removal in mountain lakes, including details on introduced species and removal techniques. We further place fish introductions in the broader context of invasive alien species in the Alps, as well as in the context of other emerging threats to mountain lakes. Additionally, we discuss the systematic mapping and review effort on which this platform rests, including the specific data available for the European Alps, along with both research needs and options for the collaborative use and development of this online resource.

ID: 3.95

Drivers of pluriannual chemical variability in high-mountain lakes of the Western Italian Alps

Michela Rogora
Tiberti, Rocco; Bello, Lucia; Giacomotti, Paola; Orru', Arianna; Tartari, Gabriele; Marchetto, Aldo; Ocleppo, Milena

Abstract/Description

Alpine lake chemical composition depends on several local and regional factors, including catchment cover. geographic and morphometric characteristics, atmospheric deposition and meteo-hydrological conditions. Local human activities may also lead to changes in the chemistry of lake water, by directly introducing allochthonous compounds, including toxic compounds, or indirectly triggering trophic cascades that can alter the lake’s trophic status. Fish introduction, livestock and other sources of nutrients and organic pollutants may indeed cause lake eutrophication or nutrient imbalances, with an overall effect on water quality.

The present study is based on 536 water samples collected over an 18-year monitoring period from 22 high altitude lakes in the protected areas of Gran Paradiso National Park and Monte Avic Natural Park. The monitoring, still ongoing, has been performed within the LIFE projects BIOAQUAE (Biodiversity improvement of Alpine aquatic ecosystems; 2012-2017) and RESQUE ALPYR (Restoration of aquatic ecosystems in protected areas in the Alps and Pyrenees; 2022- ). The study lakes are affected by several threats (livestock grazing, overtourism, introduced fish fauna) possibly interacting with each other. Sixteen lakes have been or are currently subject to fish eradication during the study period, representing an ideal direct test of the possible effects of non-native fish on nutrient concentrations.

The variability of chemical composition is assessed on a seasonal and interannual basis and analyzed in relation to environmental drivers, including lake morphology, catchment characteristics and anthropogenic pressures. Some lakes exhibit an increase in conductivity and major ions, that may be ascribed to a climate-related increase in weathering processes. Trends in nutrients are not evident, suggesting that in our study area there is no clear climate-driven increase in atmospheric nutrient deposition. We do, however, detect an effect of grazing livestock on nutrient levels, while the influence of fish presence and removal is less clear. This may indicate that lake responses to anthropogenic disturbances and restoration actions are either delayed or highly context-dependent, potentially confounded by multiple interacting factors such as benthic production and pelagic grazing. Long-term data collected with standard methods are confirmed as an invaluable tool to assess mountain lake chemical changes and their drivers.

ID: 3.121

The Lacs sentinelles network: long-term monitoring and scientific insights on French mountain lakes responses to global change

Aline Bouvier
Bruel, Rosalie; Birck, Carole; Sagot, Clotilde; Augé, Vincent; Assmann, Clémentine; Chanudet, Vincent; Bonet, Richard; Albertini, Pierre-Jean; Perga, Marie-Elodie; Vallat, Manuel; Nikolli, Alice; Cavalli, Laurent; Brena, Pierpaolo; Ré, Jordan; Revol, Nicolas; Souchier, Marine; Bourgeois, Ilann; Arthaud, Florent

Abstract/Description

Mountain lakes are sensitive ecosystems that respond rapidly to environmental and climatic forcing, making them valuable sentinels of global change. Robust, long-term data are required to assess their functioning and vulnerability, but their remoteness and heterogeneity require coordination and cooperation. Established in 2009, the Lacs sentinelles network was created to address this gap. The network aims to improve understanding of lake physical, chemical, and biological dynamics, as well as how they respond to local and global drivers, by coordinating research and monitoring on mountain lakes, in the French Alps, the French Pyrenees and Corsica. The network is first and foremost a space for different professions (scientists, managers, users) working on mountain lakes to exchange information and problematics, design and carry out research projects, and finally synthetize and share information to relevant stakeholders or the general public. By facilitating exchanges within and among professions and providing an overview of ongoing investigations, the network strengthens coherence and complementarity across projects.

A pillar of the network is its observatory, that includes 34 lakes where harmonized protocols are deployed, whose comparable data constitute a basis for studies. Recent publications investigated key mechanisms behind hypoxia onset under ice, heterogeneous phytoplankton responses to climate warming, and long-term changes in zooplankton communities driven by interactions between local pressures and global stressors.
More recently, data from the mountain lake observatory contributed to an interdisciplinary project at the scale of the French Alps to quantify microthermal responses of three compartments (rock, soil, lake) to summer heatwaves. In parallel, the network skillset expended through the contribution of researchers in social sciences, to provide an integrated assessment of changing recreational practices around mountain lakes. Specifically, analyses of human activities and social perceptions of mountain lakes were assessed through surveys while chemical indicators were monitored throughout a gradient of lakes to evaluate lakes response to human presence in and around the lakes.
Finally, the network helps to create synthesis and outreach material for stakeholders and the general public to promote scientifically sound knowledge on mountain lakes as well as relevant conservation strategies under a changing climate.

ID: 3.144

Decadal spatiotemporal suspended sediment dynamics in high-mountain lakes across the Western Alps under changing environment

Soumi Talukdar
Kropáček, Jan

Abstract/Description

Rapid deglaciation and changing climatic regime are altering the hydro-sedimentary properties of the high-mountain lakes, which act as an early indicator of global environmental changes. In this ongoing research, we present the decadal (2016-2025) spatiotemporal suspended sediment (SS) dynamics of eight high-altitude lakes and reservoirs in the Western Alps with different glacier connectivity and various levels of turbidity, situated at an average altitude of 2,000 meters a.s.l. We use reflectance in the red band (B4) as it has already been proven to be a robust proxy for suspended sediment concentration. As Sentinel-2 L2A atmospherically corrected products have limited validity for water analysis, we cross-validated snow, cloud and glint masked Top-of-the-atmosphere (TOA) red band reflectance from the Sentinel-2 L1C product with outputs from the ACOLITE atmospheric correction model and demonstrated good agreement (r²>0.8). Mann-Kendall statistics show that four lakes have an increasing trend, while other four lakes show a decreasing red band signal. Additionally, we employed spectral turbidity indices to substantiate the SS dynamics. Surprisingly, geographically proximal lakes with different glacial connectivity conditions appeared to have similar decadal SS trend. We suggest cryospheric changes, local geomorphology, and anthropogenic factors as controlling factors, which require further in-depth investigation, with an expansion of study area in other parts of the Alps. These lakes have also been chosen as strategic sites for future data sampling and model validation, before implementation to other larger high-mountain regions across the Alps and the Himalayas.

ID: 3.143

Cross-ecosystem effects of fish introductions on semi-aquatic native insectivores (European water shrew and White-throated dipper) in high-mountain lakes

Lucia Bello
Buchaca, Teresa; Corapi, Anna; Mattioli, Giorgia; Morganti, Michelangelo; Osorio, Víctor; Pou Rovira, Quim; Sabás, Ibor; Tassi, Gianluca; Ventura, Marc; Tiberti, Rocco

Abstract/Description

High-mountain lakes represent hotspot of prey subsidies that support several native insectivores. These include terrestrial taxa such as ground-dwelling invertebrates (e.g., spiders and predatory ground beetles), adult stages of amphibians, birds, and bats, which feed along shorelines or on the wing, primarily on emerging insects. More specialized semi-aquatic predators, such as shrews and dippers, directly exploit aquatic resources by diving and feeding on aquatic macroinvertebrates.

High-mountain lakes are naturally fishless, but introductions of predatory fish is a widespread threat to mountain biota such as aquatic invertebrates. In particular, fish introductions alter macroinvertebrate community composition and reduce the abundance of conspicuous benthic and nektonic taxa (e.g., Coleoptera, Trichoptera, Plecoptera), which represent the main prey for native semi-aquatic insectivores: the European water shrew Neomys fodiens, and the White-throated dipper Cinclus cinclus. We hypothesize that they may compete with introduced fish for aquatic macroinvertebrate prey, potentially leading to their competitive exclusion.

This study develops within the context of the LIFE RESQUE ALPYR project (LIFE20 NAT/ES/000369, 2022-2026), which aims to restore >20 lakes from four protected areas from the Alps and Pyrenees through mechanical fish eradication. More than 50 lakes contrasting in fish status (naturally fishless, containing non-native fish, or undergoing restoration) were monitored for prey availability and for water shrew and dipper occurrence and abundance. Monitoring was complemented with bycatch data from lakes undergoing eradication, which, although unfortunate, provided valuable insights into the recovery of native insectivore communities.

Results highlight that introduced fish can affect not only fully aquatic organisms but also semi-aquatic insectivores, which are traditionally excluded from impact assessments. This emphasizes the pervasive Impact of fish in mountain lakes and underscores the importance of conserving these ecosystems fishless.

ID: 3.141

A simple hydrodynamic model for sediment dynamic in shallow alpine lakes

Martina Viscido
Camporeale, Carlo Vincenzo; Tamea, Stefania

Abstract/Description

High mountain Alpine lakes are fundamental systems, as they provide essential ecosystem services. In glacierized catchments, they play a crucial role in regulating sediment transfer, trapping and redistributing melt-derived suspended sediments. In recent year they have become increasingly exposed to multiple environmental pressures, such as climate-driven hydrological shifts and glacier retreat, processes that alter sediment delivery. Hence, being able to model sediments dynamics become essential for anticipating ecosystem evolution and assessing how these systems respond to changing environmental forcings. Yet most of the existing hydrodynamic models are designed for large and stratified basins, not adequate for the cold-monomictic lakes typical of high altitude environments.

In our study, we present a simplified, dimensionless and radially symmetric 2D model for the sediment transport and deposition in non stratified Alpine lakes. The formulation is based on mass conservation applied to water and suspended sediment independently. To close the problem, an analytical expression for bed sediment flux has been derived through a perturbative expansion of the advection–diffusion equation in cylindrical coordinates. The resulting model is simple, fully replicable, requires a limited amount of input data, and does not need calibration.

We tested the model with both real data, collected at the Seracchi Lake (Western Italian Alps), and synthetic inputs, generated through sinusoidal forcing. Despite its simplified structure, the model effectively reproduces the observed dynamics of suspended sediment. Sensitivity analyses highlight the dominant role of the reference vertical flux, indicating that settling velocity and lake geometry exert the strongest control on model output, while the effect of grain size emerges naturally through settling velocity.

The model’s responsiveness to hydrological inputs and basin characteristics demonstrates its potential for estimating annual sediment fluxes and assessing the evolution of trapping efficiency under shifting forcings on short time scales. The analytical expression derived for bed flux also supports the estimation of annual deposition and long-term infilling dynamics, enabling the identification of silting time and predicting when a lake may transition toward a peat-forming system, with implications for its ecological function.

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FS 26.112

Mountain lakes and ponds under human pressure and global threats

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