Land Resources & Environmental Sciences
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/11
The Department of Land Resources and Environmental Sciences at Montana State Universityoffers integrative, multi-disciplinary, science-based degree programs at the B.S., M.S., and Ph.D. levels.
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Item McMurdo Dry Valley lake edge ‘moats’: the ecological intersection between terrestrial and aquatic polar desert habitats(Cambridge University Press, 2024-04) Stone, Michael S.; Devlin, Shawn P.; Hawes, Ian; Welch, Kathleen; Gooseff, Michael N.; Takacs-Vesbach, Cristina; Morgan-Kiss, Rachael; Adams, Bryon J.; Barrett, J. E.; Priscu, John C.; Doran, Peter T.Aquatic ecosystems - lakes, ponds and streams - are hotspots of biodiversity in the cold and arid environment of Continental Antarctica. Environmental change is expected to increasingly alter Antarctic aquatic ecosystems and modify the physical characteristics and interactions within the habitats that they support. Here, we describe physical and biological features of the peripheral ‘moat’ of a closed-basin Antarctic lake. These moats mediate connectivity amongst streams, lake and soils. We highlight the cyclical moat transition from a frozen winter state to an active open-water summer system, through refreeze as winter returns. Summer melting begins at the lakebed, initially creating an ice-constrained lens of liquid water in November, which swiftly progresses upwards, creating open water in December. Conversely, freezing progresses slowly from the water surface downwards, with water at 1 m bottom depth remaining liquid until May. Moats support productive, diverse benthic communities that are taxonomically distinct from those under the adjacent permanent lake ice. We show how ion ratios suggest that summer exchange occurs amongst moats, streams, soils and sub-ice lake water, perhaps facilitated by within-moat density-driven convection. Moats occupy a small but dynamic area of lake habitat, are disproportionately affected by recent lake-level rises and may thus be particularly vulnerable to hydrological change.Item Prediction of Ice-Free Conditions for a Perennially Ice-Covered Antarctic Lake(2019-02) Obryk, Maciej K.; Doran, Peter T.; Priscu, John C.Although perennially ice‐covered Antarctic lakes have experienced variable ice thicknesses over the past several decades, future ice thickness trends and associated aquatic biological responses under projected global warming remain unknown. Heat stored in the water column in chemically stratified Antarctic lakes that have middepth temperature maxima can significantly influence the ice thickness trends via upward heat flux to the ice/water interface. We modeled the ice thickness of the west lobe of Lake Bonney, Antarctica, based on possible future climate scenarios utilizing a 1D thermodynamic model that accounts for surface radiative fluxes as well as the heat flux associated with the temperature evolution of the water column. Model results predict that the ice cover of Lake Bonney will shift from perennial to seasonal within one to four decades, a change that will drastically influence ecosystem processes within the lake.Item The Impact of a Large-Scale Climate Event on Antarctic Ecosystem Processes(2016-10) Fountain, Andrew G.; Saba, Grace; Adams, Byron; Doran, Peter T.; Fraser, William; Gooseff, Michael N.; Obryk, Maciej K.; Priscu, John C.; Stammerjohn, Sharon E.; Virginia, Ross A.Extreme climate and weather events, such as a drought, hurricanes, or ice storms, can strongly imprint ecosystem processing and may alter ecosystem structure. Ecosystems in extreme environments are particularly vulnerable because of their adaptation to severe limitations in energy, water, or nutrients. The vulnerability can be expressed as a relatively long-lasting ecosystem response to a small or brief change in environmental conditions. Such an event occurred in Antarctica and affected two vastly different ecosystems: a marine-dominated coastal system and a terrestrial polar desert. Both sites experienced winds that warmed air temperatures above the 0 degrees C threshold, resulting in extensive snow and ice melt and triggering a series of cascading effects through the ecosystems that are continuing to play out more than a decade later. This highlights the sensitivity of Antarctic ecosystems to warming events, which should occur more frequently in the future with global climate warming.Item Responses of Antarctic Marine and Freshwater Ecosystems to Changing Ice Conditions(2016-10) Obryk, Maciej K.; Doran, Peter T.; Friedlaender, Ari S.; Gooseff, Michael N.; Morgan-Kiss, Rachael M.; Priscu, John C.; Schofield, Oscar; Stammerjohn, Sharon E.; Steinberg, Deborah K.; Ducklow, Hugh W.Polar regions are warming more rapidly than lower latitudes, and climate models predict that this trend will continue into the coming decades. Despite these observations and predictions, relatively little is known about how polar ecosystems have responded and will continue to respond to this change. Two Long-Term Ecological Research (LTER) sites, located in contrasting environments in Antarctica, have been studying marine and aquatic terrestrial ecosystems for more than two decades. We use data from these research areas to show that the extent and thickness of ice covers are highly sensitive to short- and long-term climate variation and that this variation significantly influences ecosystem processes in these respective environments. Declining sea-ice extent and duration diminishes phytoplankton blooms as a consequence of reduced water stratification, whereas the thinning of lake-ice cover enhances phytoplankton blooms because of increased penetrating light into the water column. Both responses have cascading effects on upper trophic levels.Item Modeling the thickness of perennial ice covers on stratified lakes of the Taylor Valley, Antarctica(2016-10) Obryk, Maciej K.; Doran, Peter T.; Hicks, J A; McKay, C P; Priscu, John C.A 1-D ice cover model was developed to predict and constrain drivers of long-termice thickness trends in chemically stratified lakes of Taylor Valley, Antarctica. The model is driven by surface radiative heat fluxes and heat fluxes from the underlying water column. The model successfully reproduced 16 a (between 1996 and 2012) of ice thickness changes for the west lobe of Lake Bonney (average ice thickness = 3.53 m) and Lake Fryxell (average ice thickness = 4.22 m). Long-term ice thickness trends require coupling with the thermal structure of the water column. The heat stored within the temperature maximum of lakes exceeding a liquid water column depth of 20 m can either impede or facilitate ice thickness change depending on the predominant climatic trend (cooling or warming). As such, shallow (<20 m deep water columns) perennially ice-covered lakes without deep temperature maxima are more sensitive indicators of climate change. The long-term ice thickness trends are a result of surface energy flux and heat flux from the deep temperature maximum in the water column, the latter of which results from absorbed solar radiation.