Investigating microbial community composition and function in glacially-fed lakes in Jostedalsbreen, Norway

Expedition Location: Sogndal, Norway

Expedition Dates: July 27, 2025 – August 8, 2025

Field Team Members: Miranda Seixas*, Kayla Guthrie, Misa Saros, Jacob Yde, Jasmine Saros

Funding Support: The Robert and Judith Sturgis Family Foundation Exploration Fund

Introduction: The cryosphere is anywhere on Earth where water is frozen, including ice sheets, ice caps, mountain glaciers, and permafrost (Boetius et al. 2015). Today the cryosphere covers about one-fifth of the planet’s surface (Fountain et al. 2012), but these icy environments are in rapid decline due to the effects of climate change, particularly in the Arctic (Boetius et al. 2015; Shukla et al. 2019; Peng et al. 2021). Over the past 40 years the Arctic has warmed four times more than the global average (Ono et al. 2022; Rantanen et al. 2022). As a result, accelerated melting of glaciers in the Arctic, including the Greenland Ice Sheet (GrIS) and Jostedalsbreen, the largest ice cap in Europe, has created new freshwater systems (Joughin et al. 2004; Dowdeswell 2006; Khan et al. 2015; Åkesson et al. 2025). Specifically, new glacially-fed lakes are forming at a rapid rate, both in the Arctic (Howat et al. 2013; How et al. 2021; Seier et al. 2024) and across the cryosphere (Buckel et al. 2018; Veettil and Kamp 2021).

Glacially-fed lakes have different environmental characteristics than non-glacially-fed lakes, meaning those sourced from snowpack or rainfall. Most glacially-fed lakes are cold and polymictic, meaning they are generally well-mixed (Peter and Sommaruga 2017). They also have low light because of high turbidity from glacial flour, a fine glacially-eroded sediment that stays suspended in the lake (Rose et al. 2014; Burpee et al. 2018). Glacially-fed lakes also have very different nutrient concentrations than non-glacially-fed lakes. Phosphorus, nitrate, and ammonium are all elevated in glacially-fed lakes compared to non-glacially-fed lakes in West Greenland (Grider et al. 2025). This trend has also been seen in alpine environments. In Norway, glacially-fed lakes fed from the Jostedalsbreen ice cap are elevated in phosphorus and nitrate (Grider, in review). Glacially-fed lakes in the Rockies, regardless of elevation, also showed high phosphorus and nitrate (Saros et al. 2010; Vanderwall et al. 2023) and glaciers in the Italian Alps export high concentrations of nitrogen and dissolved organic carbon (DOM) (Colombo et al. 2019). Many nutrients in glacially-fed freshwater systems decrease in concentration downstream of the glacial melt input, suggesting that lakes act as sinks and that the glacial system is the source of these elevated nutrients (Vanderwall et al. 2023; Grider et al. 2025). High concentrations of nutrients, particularly nitrate and phosphorus, can alter the ecology of lake ecosystems and are of concern in some systems because of the increased potential for toxic algal bloom events, with implications for ecological damage and drinking water quality.

Significance: The motivation behind this research project is the uncertainty around the source of this high concentration of nutrients, specifically nitrate, measured in glacially-fed lakes. In many freshwater systems, nitrate is produced and consumed by microbial metabolisms. To date, the contribution of microorganisms to nitrogen concentrations in glacially-fed systems has not been thoroughly studied. This study is the first in this field to directly compare the differences in microbial communities between different glacially-fed lakes in the Arctic. During this expedition, samples for nutrients and DNA were collected from lakes on the edge of Jostedalsbreen in Norway (Figure 1). The water chemistry and genetic data will identify who is present in glacially-fed lakes in Norway, what they are consuming and producing, if they have the genetic potential to produce nitrate, and how they are changing nitrogen concentrations in the glacially-fed lakes.

Methods: Fieldwork was conducted in Norway from July 27 to August 8, 2025. Three glacially-fed lakes, Brevatnet, Nigardsbrevatnet, and Styggevatnet, were sampled along the edge of Jostedalsbreen (Figure 1). All data and samples were collected from an inflatable rubber raft at the deepest part of the lake (Figure 2, Figure 3). Vertical temperature, fDOM, and chlorophyll-a concentration profiles were collected with a Turner C3 submersible fluorometer. Water samples were collected at two depths – 1) surface: bottles were submerged just under the lake surface, and 2) near bottom: samples were collected from about ¾ of the way to the bottom of the lake using a van Dorn sampler. Samples for water isotopes and conductivity measurements were collected just from the surface depth in sterile bottles. HCl-acid washed bottles were used to collect nutrients, dissolved organic carbon, and dissolved organic matter. Nitric-acid washed bottles were used to collect water for metals. Bleach washed bottles were used to collect water for subsequent DNA analysis. All bottles were rinsed three times with lake water before sample collection.

Samples for dissolved nutrients, dissolved DOC, and dissolved metals were filtered through a WHATMAN GF/F 0.7 um filter. DNA and RNA samples were filtered sequentially through first a 0.8um Isopore polycarbonate filter, and then a 0.2um sterile Pall Supor filter. Filtrate volume was measured before discarding, RNA preservation solution was added to RNA samples, and all filters were frozen at -20C until reaching the lab, then kept at -80C until extraction. All other filtered and unfiltered samples were refrigerated until analysis, with the exception of DOM which was frozen. DNA from the filters will be extracted using ZYMO’s Quick DNA Fungal/Bacterial Miniprep Kit and sequenced at the University of Minnesota’s Genomics Center for both the 16S rRNA gene and for metagenomics. Nutrients will be run at the University of Maine in the Sawyer Water Research Lab.

Broader Connections: The samples from this expedition will be analyzed alongside samples from glacially-fed lakes in Greenland and will be the first study to characterize these microbial communities by identifying who is present, what metabolisms they are capable of, and how they differ geographically. We will evaluate microorganisms as a potential source of elevated nitrate and other nutrients in glacially-fed lakes in the Arctic, furthering our understanding of how glacially-fed freshwater systems are changing in response to climate change.

Acknowledgements: Thanks to the Robert and Judith Sturgis Family Foundation Exploration Fund for supporting this research, as well as the welcoming team at the Western Norway University of Applied Sciences, specifically Dr. Jacob Yde (Figure 4) for his mentorship and dedicated support. A special thank you to Kayla Guthrie and Misa Saros for help in the field and for Jasmine Saros for her dedicated support and guidance throughout this project.

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