Polar inland waters, encompassing Arctic and Antarctic regions, are experiencing unprecedented environmental changes. Warming air temperatures and shifting precipitation patterns are leading to shortened ice durations, novel flow regimes, and altered ecosystem dynamics, affecting the biodiversity and functioning of polar lakes and rivers. This session aims to bring together scientists from diverse disciplines to share their research findings, discuss key issues, and identify future directions for understanding the implications of long-term changes on ecosystem dynamics and hydrological processes in polar environments. Through this multidisciplinary session, we aim to foster collaboration and facilitate the exchange of knowledge among researchers working on various aspects of polar limnology to better understand global change.
Lead Organizer: Hilary Dugan, University of Wisconsin–Madison (hdugan@wisc.edu)
Co-organizers:
Arial Shogren, University of Alabama (ashogren@ua.edu)
Václava (Vendy) Hazuková, University of Maine (vaclava.hazukova@maine.edu)
Presentations
05:30 PM
Evaluating ice thickness on permanently frozen Antarctic lakes with a combination of Landsat imagery and in situ measurements (7784)
Primary Presenter: Charles Dougherty, University of Wisconsin-Madison (cedougherty@wisc.edu)
The McMurdo Dry Valleys (MDVs) are the largest unglaciated region in Antarctica and are populated with permanently ice-covered lakes. These ice covers define the available habitat within the water column, providing a shield from atmospheric exchange and wind mixing events, and greatly reducing the amount of available photosynthetically active radiation. As climate change accelerates warming in the MDVs, it is critical to understand how the ice covers will be impacted since they are foundational to the aquatic habitat of this extreme ecosystem. Long-term data collection by the McMurdo Dry Valleys Long-Term Ecological Research program shows that the lake ice covers go through decadal thinning and thickening trends, ranging between 2.5 to 6.5 meters thick. These fluctuations are often thought to be driven by air temperature and changes in albedo due to aeolian sediment deposition. Although the drivers have long been identified, the actual mechanics behind these shifts in thickness are not well understood. Here, we use a combination of Landsat imagery, historical data, and high frequency in situ climate measurements to quantify the drivers regulating ice thickness in this extreme environment. Understanding how the permanent ice covers of MDV lakes function is critical in predicting how and under what conditions the lakes might change in the future as a result of climate change.
05:30 PM
GROWTH AND STRESS PHYSIOLOGY OF TWO NOVEL ANTARCTIC ALGAL ISOLATES FROM THE MCMURDO DRY VALLEYS (ANTARCTICA) (7825)
Primary Presenter: Benjamin Nagle, Miami University (naglebf@miamioh.edu)
The permanently ice-covered lakes of the McMurdo Dry Valleys (MDV) in Antarctica have been the subject of three decades of ecological research (mcmlter.org). These lakes harbor diverse and unique microbial communities which are exposed to permanent extreme conditions including cold, high salinity, and variable light levels. This ecosystem is largely supported by cold-adapted (psychrophilic) phytoplankton, many of which have yet to be isolated. Despite the remote location of the MDV, it still experiences the effects of climate change; however, it is not well understood how microbial communities will respond. To contribute to the preservation and characterization of novel microorganisms, this research focuses on two novel algae isolates that were recently collected from Lake Fryxell. Sequencing of 18S rRNA identified the strains as Ulothrix and Chlorella. Both strains are novel in this lake, moreover, the Ulothrix isolate is the first filamentous algae to be isolated from Lake Fryxell. The algal isolates both show exponential growth in defined medium under batch culture conditions. Preliminary growth physiology indicates that both strains are psychrophilic. Growth stress physiology under environmentally relevant conditions will be discussed to better understand these novel isolates and their response to a variety of abiotic environmental stressors.
05:30 PM
MICROFUNGAL DISTRIBUTION & INTERACTIONS IN ANTARCTIC LAKE BONNEY ACROSS SEASONAL AND SPATIAL SCALES (7827)
Primary Presenter: Eckhardt Karsten, Miami University (karsteea@miamioh.edu)
Fungi are recognized as critical players in terrestrial ecosystems, though their role in aquatic ecosystems has been historically understudied. Improved molecular techniques have allowed for advancements to be made in understanding aquatic fungal ecology and the larger impact they have on protists and microbial food webs. As saprotrophs and parasites of algae, fungi can have major consequences on the carbon cycling of an aquatic system, especially those dependent on autochthonous carbon such as ice-covered lakes. The McMurdo Dry Valleys of Antarctica (MDVs) represent one of the driest and coldest deserts in the world, housing a collection of perennially ice-covered lakes. These lakes are natural laboratories for exploring microbial interactions, though research has been largely limited to the austral summer due to the difficulty of accessing the region in winter. The deployment of a suite of Autonomous Lake Profile Samplers (ALPS) into Lake Bonney has enabled the collection of physicochemical & biological samples about every three weeks over an entire year. The ALPS project provides an opportunity to explore seasonal changes in microbial community structure and potential interactions. By exploring diversity metrics and generating association networks, fungal diversity and function can be assessed across depth and season which allows for a clearer view on the microbial loop within polar lakes. Preliminary 18S rRNA gene amplicon data suggests that pathogenic fungi are significant network members across all seasons, increasing in connectivity with the onset of polar night.
05:30 PM
IMPACT OF SALINITY VARIATION ON NATIVE LAKE COMMUNITIES FROM LAKE BONNEY (MCMURDO DRY VALLEYS, ANTARCTICA) (7828)
Primary Presenter: Rochelle Pereira, Miami University (pereirrp@miamioh.edu)
The McMurdo Dry Valleys (MDVs), Antarctica, harbor lakes with year-round liquid water columns isolated under thick permanent ice covers that exhibit extreme conditions (e.g. nutrient deficiency, high salinity, low temperature). Chemistry and biology in the water column have been stratified for hundreds of years, and each lake contains a unique food web dominated by the microbial loop. Warmer summers bring significant environmental change in the form of glacial melt and thinning ice covers. Streams transport glacial melt to the lakes, increasing freshwater input and causing lake level rise. The site of study, Lake Bonney, is hypersaline and the introduction of freshwater (“freshening”) poses a stressor on the high salt-adapted organisms. We used a bioassay approach to investigate the impact of environmentally relevant salinity variation on microbial communities of Lake Bonney. We focused on the responses of three dominant phytoplankton, Isochrysis sp. MDV (haptophyte), Chlamydomonas sp. ICE-MDV (chlorophyte) and Geminigera sp. (cryptophyte). When compared to control conditions, chlorophyte populations were negatively impacted under freshening conditions and had higher abundances under higher salt concentrations. In contrast, haptophytes were abundant under freshening conditions. Our results indicate that major phytoplankton taxa will be significantly impacted by climate-associated melt. The cascading impact of shifts in primary producers on the bacterial communities will be discussed.
05:30 PM
THE INFLUENCE OF ENVIRONMENTAL DISTURBANCE ON PHYCOSPHERE-ASSOCIATED BACTERIA FROM ANTARCTIC LAKES (7824)
Primary Presenter: Bradley Krzysiak, Miami University (krzysibm@miamioh.edu)
The phycosphere is the interface for complex networks of interactions between algae and their bacterial partners. These interactions primarily involve the exchange of metabolites. Algae commonly share fixed organic carbon in the form of small metabolites with their bacterial counterparts, often in exchange for compounds benefiting algal growth (e.g. phytohormones, vitamins, micronutrients). The phycosphere is also a site of negative interactions: for example, production of algicidal or antibacterial compounds under nutrient limiting conditions. Lakes within the McMurdo Dry Valleys (MDV), Antarctica, represent some of the last perennially ice-covered lakes on the planet. Algae-bacteria interactions within the water column of the MDV lakes are of high interest: the food web is entirely microbial and fixed carbon is almost entirely autochthonous. The lack of external inputs into these lakes places a greater importance on the photosynthetic algae within them as major organic carbon producers. In this project, we first developed cultures from East Lake Bonney and Lake Fryxell using defined autotrophic growth media to enrich algae-bacteria interactions. Then we tested the impact of nutrient deprivation on the stability of algae-bacteria interactions using size fractionation filtration followed by 16S and 18S rRNA sequencing. Our preliminary findings indicate that while there are specific bacterial taxa associated with MDV phytoplankton, MDV algae-bacteria interactions are not significantly impacted by nutrient status.
05:30 PM
THE IMPACT OF BACTERIAL CONSORTIA ON STRESS RESPONSE OF ANTARCTIC PHYTOPLANKTON (7826)
Primary Presenter: Dom Marichal, Miami University (marichda@miamioh.edu)
The McMurdo Dry Valley lakes, located in the Taylor Valley, Antarctica, are permanently ice-covered lakes that house unique, isolated ecosystems. The organisms that live there need to contend with a variety of stressors and extreme conditions, including low temperatures, limited nutrient availability, and extreme shade. These sites are unique examples of natural gradients of stress. The ice cover prevents mixing, leading to steep chemical gradients, including concentrations of salt, with hypersaline depths and fresh water near the ice. These gradients, along with the lack of macroorganisms and minimal external inputs, make these lakes natural laboratories for studying the relationship between environmental stressors and community interactions. We developed phytoplankton-bacteria enrichment cultures in autotrophic media from samples taken from Lake Bonney at depths of low and high salinity. We then compared stress response in the enrichment cultures versus Chlamydomonas spp. isolates to a salinity gradient. Cultures were grown under a gradient of salinity to observe salt stress. Optical density was used to measure overall growth, photosystem measurements and RT-qPCR were used to measure indicators of stress, and 16s sequencing of the enrichments was done to observe the impacts of stress on the community composition.
05:30 PM
PONDS AND SMALL, SHALLOW LAKES AS HOTSPOTS OF ORGANIC CARBON CYCLING ACROSS PERMAFROST GRADIENTS (8362)
Primary Presenter: Emily Peterson, University of Alaska Fairbanks (peterson.emily238@gmail.com)
Across Arctic and boreal regions, anthropogenic activity is responsible for increasing temperatures, vegetation expansion, and permafrost thaw. Ponds and shallow lake areas are increasing across permafrost influenced environments, potentially augmenting regional carbon cycling. These very small water bodies are tightly linked to the land, making them highly responsive to environmental changes driven by anthropogenic activity. To monitor seasonal changes in dissolved organic matter (DOM) composition in ponds and small, shallow lakes, we collected biweekly surface water samples at 12 sites across a gradient of underlying permafrost, ground-ice content, and soil organic carbon near Fairbanks, Alaska. We operationally defined ponds as bodies with surface area less than .01 km2 and shallow lakes as greater than or equal to 0.01 km2, and less than 5 meters in depth. We measured dissolved organic carbon concentrations, DOM absorbance and fluorescence, and water isotopes as a proxy for hydrologic connectivity to assess the variability in DOM composition across heterogeneous landscapes and hydrologic connectivity. Composition was variable across sites and seasons; in small lakes DOC and absorbance at 254 nm were strongly correlated whereas ponds seasonally deviated from the relationship. We also found that DOM composition changed significantly across the seasons and interannually indicating that these sites are extremely responsive to the environmental condition.
SS29P - Limnology of Polar Environments
Description
Time: 5:30 PM
Date: 4/6/2024
Room: Madison Ballroom D