Desert Potholes: Ephemeral Aquatic Microsystems |
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| Authors: | Email author" target="_blank">Marjorie?A?ChanEmail author Katrina?Moser Jim?M?Davis Gordon?Southam Kebbi?Hughes Tim?Graham |
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| Institution: | (1) Department of Geology & Geophysics, University of Utah, Salt Lake City, UT 84112, USA;(2) Department of Geography, University of Utah, Salt Lake City, UT 84112, USA;(3) Department of Earth Sciences, The University of Western Ontario, London, Ontario, N6A 5B7, Canada;(4) U.S. Geological Survey, 82 Dogwood Ave., Moab, UT 84532, USA |
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| Abstract: | An enigma of the Colorado Plateau high desert is the “pothole”, which ranges from shallow ephemeral puddles to deeply carved
pools. The existence of prokaryotic to eukaryotic organisms within these pools is largely controlled by the presence of collected
rainwater. Multivariate statistical analysis of physical and chemical limnologic data variables measured from potholes indicates
spatial and temporal variations, particularly in water depth, manganese, iron, nitrate and sulfate concentrations and salinity.
Variation in water depth and salinity are likely related to the amount of time since the last precipitation, whereas the other
variables may be related to redox potential. The spatial and temporal variations in water chemistry affect the distribution
of organisms, which must adapt to daily and seasonal extremes of fluctuating temperature (0–60 °C), pH changes of as much
as 5 units over 12 days, and desiccation. For example, many species become dormant when potholes dry, in order to endure intense
heat, UV radiation, desiccation and freezing, only to flourish again upon rehydration. But the pothole organisms also have
a profound impact on the potholes. Through photosynthesis and respiration, pothole organisms affect redox potential, and indirectly
alter the water chemistry. Laboratory examination of dried biofilm from the potholes revealed that within 2 weeks of hydration,
the surface of the desiccated, black biofilm became green from cyanobacterial growth, which supported significant growth in
heterotrophic bacterial populations. This complex biofilm is persumably responsible for dissolving the cement between the
sandstone grains, allowing the potholes to enlarge, and for sealing the potholes, enabling them to retain water longer than
the surrounding sandstone. Despite the remarkable ability of life in potholes to persist, desert potholes may be extremely
sensitive to anthropogenic effects. The unique limnology and ecology of Utah potholes holds great scientific value for understanding
water–rock–biological interactions with possible applications to life on other planetary bodies. |
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| Keywords: | potholes desert Colorado Plateau sandstone Utah microorganisms redox biofilm cyanobacteria limnology |
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