Soil Microbial Communities In An Antarctic Water Track: Identifying Potential Ecological Optimums In a Hyperarid Mars-Analog Environment

Abstract

Polar permafrost environments commonly feature “water tracks,” areas of heightened soil moisture in which water is routed downslope above an ice-cemented permafrost interface. Water tracks are active sites of chemical weathering and possible hotspots of biological activity. Occurring in cold, arid environments, water tracks have seasonal and morphological similarities to recurrent slope lineae (RSL) streaks observed on steep equator-facing slopes of Mars. Water tracks are also potential analogs of ephemeral streams and rivers that likely featured in the cold, icy climate of the late Noachian period of early Mars. This study aims to characterize microbial communities within water track soils, looking specifically at community structures and predicted functional differences. Prior studies of water tracks in the McMurdo Dry Valleys in Antarctica have identified increased organic matter and biotic respiration of CO2 within track soils. To identify possible ecological optimums within the studied water track in East Antarctica, community composition was compared at various elevations within the track and in off-track control soils. Community composition was not found to vary significantly between track and control soils, with Actinobacteria, Chloroflexi and Proteobacteria dominant across all sampling sites; however, gene expression within these clades may increase significantly with hydration, a hypothesis that will be tested as part of future work with transcriptomics. Interestingly, we found significant proportions of unclassified taxa in collected samples (over half of the results at the family level). Further study will expand whPolar permafrost environments commonly feature “water tracks,” areas of heightened soil moisture in which water is routed downslope above an ice-cemented permafrost interface. Water tracks are active sites of chemical weathering and possible hotspots of biological activity. Occurring in cold, arid environments, water tracks have seasonal and morphological similarities to recurrent slope lineae (RSL) streaks observed on steep equator-facing slopes of Mars. Water tracks are also potential analogs of ephemeral streams and rivers that likely featured in the cold, icy climate of the late Noachian period of early Mars. This study aims to characterize microbial communities within water track soils, looking specifically at community structures and predicted functional differences. Prior studies of water tracks in the McMurdo Dry Valleys in Antarctica have identified increased organic matter and biotic respiration of CO2 within track soils. To identify possible ecological optimums within the studied water track in East Antarctica, community composition was compared at various elevations within the track and in off-track control soils. Community composition was not found to vary significantly between track and control soils, with Actinobacteria, Chloroflexi and Proteobacteria dominant across all sampling sites; however, gene expression within these clades may increase significantly with hydration, a hypothesis that will be tested as part of future work with transcriptomics. Interestingly, we found significant proportions of unclassified taxa in collected samples (over half of the results at the family level). Further study will expand whPolar permafrost environments commonly feature “water tracks,” areas of heightened soil moisture in which water is routed downslope above an ice-cemented permafrost interface. Water tracks are active sites of chemical weathering and possible hotspots of biological activity. Occurring in cold, arid environments, water tracks have seasonal and morphological similarities to recurrent slope lineae (RSL) streaks observed on steep equator-facing slopes of Mars. Water tracks are also potential analogs of ephemeral streams and rivers that likely featured in the cold, icy climate of the late Noachian period of early Mars. This study aims to characterize microbial communities within water track soils, looking specifically at community structures and predicted functional differences. Prior studies of water tracks in the McMurdo Dry Valleys in Antarctica have identified increased organic matter and biotic respiration of CO2 within track soils. To identify possible ecological optimums within the studied water track in East Antarctica, community composition was compared at various elevations within the track and in off-track control soils. Community composition was not found to vary significantly between track and control soils, with Actinobacteria, Chloroflexi and Proteobacteria dominant across all sampling sites; however, gene expression within these clades may increase significantly with hydration, a hypothesis that will be tested as part of future work with transcriptomics. Interestingly, we found significant proportions of unclassified taxa in collected samples (over half of the results at the family level). Further study will expand what is known about the functional diversity of these unique Martian analog environments.