@article {5021, title = {Chemical signatures of microbial life in an ecological end-member: Shifting hydroclimate and sediment fluxes influence DOM biogeochemistry in Lake Fryxell, a permanently ice-covered lake in the McMurdo Dry Valleys of Antarctica}, journal = {Arctic, Antarctic, and Alpine Research}, volume = {57}, year = {2025}, month = {04/2025}, pages = {2478678}, abstract = {

The ice-covered lakes in the McMurdo Dry Valleys (MDV) of Antarctica provide end-member ecosystems for understanding the production of dissolved organic matter (DOM) in aquatic ecosystems in the absence of vegetation on the landscape and under resource and nutrient constraints. Given these constraints, DOM in MDV lakes is derived solely from microbial phototrophs and heterotrophic bacteria, contrasting with the dominant terrestrial sources in temperate regions. Previous research developed fluorometric approaches for characterizing DOM, including in MDV lakes. In this study we leveraged these approaches along with contemporary molecular-based techniques to elucidate changes in DOM composition across the depth profile for Lake Fryxell in the MDV. The results showed that the presence of organic molecules containing sulfur increased at depth where anoxic conditions prevailed. To evaluate the influences of climate-induced rising lake levels and multiple flood events in the MDV, we compared recent and historical samples. The results indicated a remarkable consistency in source-related fluorescence metrics over time, whereas a twofold decrease in sulfur content of the fulvic acid fraction was observed in samples from above and below the oxycline. Biogeochemical processes associated with the influx of iron oxide\–rich sediments during flood events may have contributed to this change, and similar processes may stimulate biogeochemical cycling and remineralization in temperate lakes during seasonal transitions.

}, keywords = {LTER-MCM, Antarctica, biogeochemistry, DOM, lake metabolism, limnology, nutrient cycling}, doi = {10.1080/15230430.2025.2478678}, url = {https://www.tandfonline.com/doi/full/10.1080/15230430.2025.2478678}, author = {Garrett P. Rue and Diane M. McKnight} } @article {5022, title = {One-hundred fundamental, open questions to integrate methodological approaches in lake ice research}, journal = {Water Resources Research}, volume = {61}, year = {2025}, month = {05/2025}, pages = {e2024WR039042}, abstract = {

The rate of technological innovation within aquatic sciences outpaces the collective ability of individual scientists within the field to make appropriate use of those technologies. The process of in situ lake sampling remains the primary choice to comprehensively understand an aquatic ecosystem at local scales; however, the impact of climate change on lakes necessitates the rapid advancement of understanding and the incorporation of lakes on both landscape and global scales. Three fields driving innovation within winter limnology that we address here are autonomous real-time in situ monitoring, remote sensing, and modeling. The recent progress in low-power in situ sensing and data telemetry allows continuous tracing of under-ice processes in selected lakes as well as the development of global lake observational networks. Remote sensing offers consistent monitoring of numerous systems, allowing limnologists to ask certain questions across large scales. Models are advancing and historically come in different types (process-based or statistical data-driven), with the recent technological advancements and integration of machine learning and hybrid process-based/statistical models. Lake ice modeling enhances our understanding of lake dynamics and allows for projections under future climate warming scenarios. To encourage the merging of technological innovation within limnological research of the less-studied winter period, we have accumulated both essential details on the history and uses of contemporary sampling, remote sensing, and modeling techniques. We crafted 100 questions in the field of winter limnology that aim to facilitate the cross-pollination of intensive and extensive modes of study to broaden knowledge of the winter period.

}, keywords = {LTER-MCM, cryosphere, lake ice, limnology, modeling, remote sensing}, issn = {0043-1397}, doi = {10.1029/2024WR039042}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024WR039042}, author = {Culpepper, Joshua and Sharma, Sapna and Gunn, Grant and Magee, Madeline R. and Meyer, Michael F. and Anderson, Eric J. and Arp, Chris and Cooley, Sarah W. and Dolan, Wayana and Hilary A. Dugan and Duguay, Claude R. and Jones, Benjamin M. and Kirillin, Georgiy and Ladwig, Robert and Lepp{\"a}ranta, Matti and Long, Di and Magnuson, John J. and Pavelsky, Tamlin and Piccolroaz, Sebastiano and Robertson, Dale M. and Steele, Bethel G. and Tom, Manu and Weyhenmeyer, Gesa A. and Woolway, R. Iestyn and Xenopoulos, Marguerite A. and Yang, Xiao} } @article {4998, title = {Antarctic lake viromes reveal potential virus associated influences on nutrient cycling in ice-covered lakes}, journal = {Frontiers in Microbiology}, volume = {15}, year = {2024}, month = {09/2024}, abstract = {

The McMurdo Dry Valleys (MDVs) of Antarctica are a mosaic of extreme habitats which are dominated by microbial life. The MDVs include glacial melt holes, streams, lakes, and soils, which are interconnected through the transfer of energy and flux of inorganic and organic material via wind and hydrology. For the first time, we provide new data on the viral community structure and function in the MDVs through metagenomics of the planktonic and benthic mat communities of Lakes Bonney and Fryxell. Viral taxonomic diversity was compared across lakes and ecological function was investigated by characterizing auxiliary metabolic genes (AMGs) and predicting viral hosts. Our data suggest that viral communities differed between the lakes and among sites: these differences were connected to microbial host communities. AMGs were associated with the potential augmentation of multiple biogeochemical processes in host, most notably with phosphorus acquisition, organic nitrogen acquisition, sulfur oxidation, and photosynthesis. Viral genome abundances containing AMGs differed between the lakes and microbial mats, indicating site specialization. Using procrustes analysis, we also identified significant coupling between viral and bacterial communities (p = 0.001). Finally, host predictions indicate viral host preference among the assembled viromes. Collectively, our data show that: (i) viruses are uniquely distributed through the McMurdo Dry Valley lakes, (ii) their AMGs can contribute to overcoming host nutrient limitation and, (iii) viral and bacterial MDV communities are tightly coupled.

}, keywords = {LTER-MCM, Antarctica, bacteria, limnology, metagenomics, virus}, doi = {10.3389/fmicb.2024.1422941}, url = {https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1422941/full}, author = {Robinson, David M. and Rachael M. Morgan-Kiss and Wang, Zhong and Cristina D. Takacs-Vesbach} }