Mountain lakes sit at the high-elevation confluence of the atmosphere, cryosphere, and hydrosphere, where environmental change can be rapid. Much of the change is driven by elevation-dependent warming, thawing glaciers, orographically enhanced precipitation, and increased atmospheric deposition of acids, metals, contaminants, and nutrients. The steep elevation gradients and comparatively high heterogeneity in landscape characteristics of mountain regions make their lakes ideal study systems for understanding mechanistic linkages, interactive effects, and cross-scale interactions among environmental drivers.
Our session seeks to report on responses of mountain lakes to global change across spatial and temporal scales. We aim to highlight the value of mountain lakes for understanding mechanisms underpinning lake processes more broadly. We welcome research that explores species and/or ecosystem responses to environmental change, including analyses of long-term datasets, space-for-time substitutions, field surveys, and model-driven analyses. This includes studies of community composition, food web structure, or trait-based responses in planktonic, benthic, or littoral taxa, ranging from microbes to fishes. Studies that explore linkages between terrestrial, atmospheric, and aquatic habitats, including ponds and streams, are particularly encouraged, especially those that integrate across multiple lakes, watersheds, or climatic gradients. We hope to include work ranging from fine-scale experiments to regional syntheses and macrosystems ecology. Contributions using stable isotopes, remote sensing, sensor networks, or process-based modeling are invited, as are those employing genomic, trait-based, or biogeochemical approaches. We also encourage studies that couple observational data with models or integrate ecological, hydrological, and climatological perspectives to examine how physical, chemical, and biological processes interact across system boundaries.
Lead Organizer: Steven Sadro, University of California, Davis (ssadro@ucdavis.edu)
Co-organizers:
Isabella Oleksy, University of Colorado Boulder (isabella.oleksy@colorado.edu)
Katrina Eyvindson, University of Western Ontario (katrina.eyvindson@uwo.ca)
Sudeep Chandra, University of Nevada, Reno (sudeep@unr.edu)
Presentations
11:00 AM
SENSITIVITY OF LONG-TERM ECOLOGICAL DATA: AN ANALYSIS OF THE EFFECTS OF REDUCED SAMPLING FREQUENCY ON WATER QUALITY TRENDS IN A MOUNTAIN WATERSHED (11862)
Primary Presenter: Adeline Kelly, University of Colorado (adelinekelly04@gmail.com)
Long-term ecological data are critical for understanding ecosystem responses to climate change and are stronger drivers of environmental policy and resource management than short-term studies. Such datasets are especially important for high-elevation systems, where warming is amplified and lakes are coupled with the cryosphere, yet these datasets are costly to maintain. As both ecosystems and monitoring programs face growing threats, there is a need to establish and maintain long-term monitoring programs that minimize costs while maximizing captured variation and abilities to make ecological inferences. Using a 30+ year aquatic biogeochemical record from the Loch Vale watershed in Rocky Mountain National Park, we evaluate how reduced sampling frequency affects trends and variability in long-term data. We statistically subsampled the historical weekly time series to fortnightly and monthly frequencies and assessed changes in estimated trends in major cations and in distributions and variability of nitrate fluxes annually and during snowmelt, baseflow, and winter. Preliminary results show that estimated trends in solutes indicative of weathering are largely preserved when sampling frequency is reduced, though inference strength can weaken. In contrast, nitrate concentrations and N flux estimates are sensitive to statistical downsampling, especially during hydrologically variable periods. These results highlight the need to collect long-term data at frequencies aligned with research goals and to guide adaptation of monitoring programs for personnel maintaining these datasets.
11:00 AM
CHANGES IN PRIMARY PRODUCER PIGMENT COMPOSITION AND ASSOCIATED PALEOECOLOGICAL/CLIMATOLOGICAL DRIVERS IN LAKE CINILI, THE TAURUS MOUNTAINS, TURKIYE (11627)
Primary Presenter: Hasan Arslan, Middle East Technical University (arslan.hasan@metu.edu.tr)
Alpine Lake sediments may contain a record of past climatic changes unaffected by human activity. We conducted the first large-scale paleoecological sampling in Anatolian alpine lakes between 2019-2023, collecting 15 sediment cores. Here, we present multiproxy results from an 85 cm core in Lake Çinili (11 m deep at 2667 m a.s.l.) and reconstruct its paleoecological history. C-14 dating of pollen suggests the core is approximately 2200 years old, with a possibly high reservoir age. Pigment analysis identified a total of 13 pigments, with high cyanobacterial pigment levels between 2200 and 800 BP. Diatom contribution has increased over the past 450 years. CN and XRF analyses showed significant fluctuations in organic matter and terrestrial input over time, with an overall decline in allochthonous carbon. The Mn/Fe ratio indicated abrupt water level drops and potential droughts between 649 and 410 BP. The alloxanthin/diatoxanthin ratio also reflected changes in water level linked to precipitation shifts. Clustering of pigments identified four periods aligning with the Roman Climatic Optimum, Medieval Climate Anomaly, and Little Ice Age. Overall, Lake Çinili experienced notable changes in water level and primary producer composition over the last 2200 years, demonstrating that regional climate fluctuations significantly impact the lake ecosystem. Results suggest that climate fluctuations in the region have a pronounced effect on the Lake Çinili ecosystem and Alpine lakes in Anatolia may serve as a potential paleoecological record.
11:00 AM
TESTING THE ECOSYSTEM SIZE AND PRODUCTIVE SPACE HYPOTHESES IN ALPINE LAKES (11162)
Primary Presenter: Christine Parisek, University of California - Davis (caparisek@ucdavis.edu)
This study evaluates two competing hypotheses for what regulates the architecture of food webs in California mountain lakes: ecosystem size or productivity. We measured food chain length and six multidimensional isotopic niche space measures in 36 mountain lakes representing varying lake volume and productivity dynamics. We demonstrate a modicum of support for the ecosystem size hypothesis, but no support for the productive space hypothesis. Across lakes ranging vastly in volume (8,773 – 3,999,753 m3), food chain length, and all multidimensional isotopic space niche measures showed positive trends with ecosystem size. However, only three measures (trophic area, niche centroid distance, and δ13C range) scaled significantly. There were no significant relationships between lake productivity and any of the six community niche metrics. Aquatic insects supported fish consumers in all lakes. However, reliance of consumer fishes on terrestrial insects and periphyton increased significantly and non-linearly with lake size, while reliance on aquatic plants showed opposite trends. These results expand understanding of the biogeography of aquatic food webs, and contextualize how ecosystem size and productivity drive trophic links in mountain lakes specifically.
11:00 AM
WARDENS, BARRIERS AND PERSISTENCE: MECHANISMS DRIVING ZOOPLANKTON SPECIES COMPOSITION OF HIGH ALPINE LAKES (10612)
Primary Presenter: Florian Hohenberger, University of Salzburg (florian.hohenberger@plus.ac.at)
Zooplankton species in high alpine lakes face harsh conditions in extreme environments, with low productivity and short ice-free periods. Due to warming in alpine regions these hostile environments are rapidly changing, with earlier ice out, increasing water temperatures, and potential changes in productivity and accessibility. This has the possibility to both create habitats more amenable to lowland zooplankton species and to provide more opportunities for lowland species to colonize these habitats, leading to alternate species composition in the lakes. Potential barriers to colonization (competitive exclusion, harsh environments), as well as the concept of species sorting within the zooplankton community of the lakes of the National Park Hohe Tauern, Austria, have been investigated, with the following hypotheses: 1. When large zooplankton species are already present in a lake, they can preclude invasion by new lowland species through competitive exclusion. 2. The hostile environment (low temperature and productivity, high turbidity) of some high alpine lakes is limiting the colonization success of invading species. 3. Species sorting occurs, in that the species or clones found in a lake are those best adapted to the habitat in which they were found. Based on the results of the long-term monitoring of 18 lakes of the National Park Hohe Tauern, Austria, model lakes were chosen and the water and species from these lakes used to run experiments in the lab under controlled conditions.
11:00 AM
USING SUBARCTIC ATLIN LAKE AS A SPACE-FOR-TIME MODEL FOR DIMINISHING GLACIAL INPUTS TO LARGE MOUNTAIN LAKES (10285)
Primary Presenter: Jessica Serbu, University of Ottawa (jserbu@uottawa.ca)
Glacier meltwaters are an important source of nutrients, labile carbon, and cold waters to aquatic organisms in downstream freshwater systems. Atlin Lake is a large (791 km2 area) subarctic lake in Yukon and British Columbia, Canada within the Traditional Territories of the Taku River Tlingit (TRTFN) and Carcross/Tagish First Nations (C/TFN). The southern end of Atlin Lake is fed by the Juneau Icefield and other glaciers of the Coast Mountains, while the northern end is glacier-free and fed by streams from forested boreal catchments. Importantly, the outflow occurs mid-lake, separating the southern and northern ends and supporting a natural space-for-time design within a single system that allows us to predict how the southern glacier-fed end of Atlin Lake will change over time. With the glaciers feeding Atlin Lake predicted to be 60% gone by 2100, questions remain about the impact of climate change on the function of Atlin Lake. We comprehensively sampled physical (e.g., temperature, dissolved oxygen, pH), chemical (e.g., nutrients, carbon), and biological (e.g., phytoplankton pigments and speciation, zooplankton speciation and isotopes) parameters, notably from both open-water (i.e., summer) and below-ice (i.e., winter) depth-profiling in the northern (80 m) and southern (270 m) ends of Atlin Lake. Preliminary pigment results indicate that the northern end of Atlin Lake is nearly twice as productive as the southern end. Therefore, working closely with TRTFN and C/TFN, we seek to answer the critical question of how Atlin Lake – and other glacier-fed alpine lakes globally – will adapt to climate change.
11:00 AM
Warming-induced release of benthic nutrients in mountain lakes: an incubation experiment (11649)
Primary Presenter: Ilann Bourgeois, USMB (ilann.bourgeois@univ-smb.fr)
Mountain lakes are generally extremely oligotrophic, which limits the production of aquatic biomass and gives them the crystal-clear waters that make them popular tourist destinations. Recently, stakeholders involved in the French Lacs Sentinelles network (https://www.lacs-sentinelles.org) have observed a proliferation of benthic algae in the littoral zones of high-altitude lakes. These observations echo recent studies documenting a proliferation of benthic algae in many oligotrophic lakes around the world, whether located in lowlands or in mountains1,2. Among the various hypotheses proposed to explain this phenomenon, the interaction between the pronounced warming of high-altitude lakes and nutrients’ cycling is to date the most likely explanation yet to be tested3,4. Here, we test whether the increasing temperature of littoral zones in mountain lakes can trigger the release of nutrients contained in sediments to the water column. In spring 2025, littoral sediment cores were collected before ice melt in two mountain lakes (one forested, one proglacial) in the French Alps and brought back to the lab. The cores were then either submitted to increasing temperatures in a ~2-week incubation experiment (n=4, treatment group) or kept cold (n=4, control group) and were analyzed for the chemical composition of the overlying water at regular intervals. Increasing temperature induced a significant release of sediment ammonium to the overlying water for the forested lake, but not for the proglacial lake. Both lakes exhibited similarly decreasing nitrate concentration with warming, but no significant evolution of phosphate was measured. Analysis of the temperature sensitivity (Q10) of sediment microbial respiration revealed a significant temperature influence for the forested lake (Q10=2) but not for the proglacial lake (Q10≤1). These preliminary results highlight the potential importance of temperature as a driver of nutrient cycling in littoral sediments of mountain lakes. 1. Vadeboncoeur, Y. et al. Blue Waters, Green Bottoms: Benthic Filamentous Algal Blooms Are an Emerging Threat to Clear Lakes Worldwide. BioScience 71, 1011–1027 (2021). 2. Oleksy, I. A., Baron, J. S., Leavitt, P. R. & Spaulding, S. A. Nutrients and warming interact to force mountain lakes into unprecedented ecological states. Proc. R. Soc. B. 287, 20200304 (2020). 3. Oleksy, I. A., Baron, J. S. & Beck, W. S. Nutrients and warming alter mountain lake benthic algal structure and function. Freshwater Science 40, 88–102 (2021). 4. Hampton, S. E. et al. Warming-induced changes in benthic redox as a potential driver of increasing benthic algal blooms in high-elevation lakes. Limnology and Oceanography Letters 9, 1–6 (2024).
11:00 AM
THE MOUNTAIN FUTURES YOUTUBE CHANNEL: SHARING MOUNTAIN SCIENCE WITH A GLOBAL AUDIENCE (11686)
Primary Presenter: Scott Hotaling, Utah State University (scott.hotaling@usu.edu)
Mountain landscapes are critical to the well-being of billions of people, yet they are often remote and difficult to access which makes it hard for people to connect to them. Still, incredible research is happening in mountains, including in the lakes and rivers they support. Despite the rich and important potential for storytelling, the people doing mountain research often exist in relative anonymity for the public. In 2024, I launched the Mountain Futures YouTube channel with a simple goal: raising the global profile of mountain science and the people studying these critical ecosystems. With no filmmaking experience, it has been a lesson in learning by doing. Just over a year in, we’ve grown to 600 subscribers from around the world and our videos have been watched more than 90,000 times. In our view, this is just the beginning. For this poster presentation, I will share the premise behind the channel and the plan for how we will sustain and grow it into the future. I will also invite mountain researchers—particularly those studying mountain lakes, streams, and the cryosphere—to connect with our team and perhaps be featured in a future video. If nothing else, I hope this poster will encourage mountain limnologists to think outside of the science communication box and pursue new avenues to share their work.
11:00 AM
The Effects of Rock Glacier Meltwater on Thermal Regimes and Nutrient Characteristics in Alpine Lakes in the Uinta Mountains, USA: Preliminary Findings (11107)
Primary Presenter: Chad Dickson, University of Western Ontario (cdicks26@uwo.ca)
Climate-induced warming represents a significant threat to alpine lakes, including rock glacier lakes. Warming temperatures increase the melt rate of rock glaciers, increasing the relative hydrological contribution of meltwater to adjacent lakes and streams. Our research focuses on the following question: How have warming-induced meltwater contributions from adjacent rock glaciers impacted the thermal regime and nutrient characteristics of lakes in the Uinta Mountains, USA? To investigate this, we analyzed sedimentary chlorophyll a and changes in diatom community composition in a 210Pb-dated sediment core from Gail Lake, a rock-glacier adjacent lake in Uinta Mountains, to infer environmental changes over the last several centuries. Our research indicates that despite enhanced nitrate loading from meltwater, evidenced by the dominance of Asterionella formosa in the uppermost sediments, rock glacier lakes have not experienced concomitant increases in contemporary primary production. Moreover, we find that rock glacier lakes are predominantly characterized by low water clarity and a shallow mixed layer, evidenced by the presence of Discostella stelligera throughout these sediment cores. We suggest that while rock glacier meltwater increases the availability of nitrate, it simultaneously contributes to cold, turbid lake conditions that limit primary production. Our research advances understandings of the effects of rock glacier meltwaters on alpine lake ecosystems at a critical time, as warming increases the hydrological impact of rock glaciers on alpine catchments around the world.
SS033P Science at the Source: Mountain Lakes as Natural Laboratories for Understanding Global Change
Description
Time: 11:00 AM
Date: 15/5/2026
Room: 517C