Aeolian flux of microorganisms in the McMurdo Dry Valleys, Antarctica

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Marie Sabacka
John C. Priscu
Mark C. Greenwood

The McMurdo Dry Valleys in Antarctica (MCM) forms one of the most extreme deserts on Earth. It consists of a mosaic of permanently ice-covered lakes, ephemeral streams, exposed soils, and glaciers. Microorganisms are the only life forms occupying these landscape units. Given the relatively low and seasonal growth rates of these organisms, we contend that the distribution of microorganisms within this environment is controlled by physical factors. We tested the hypotheses that biodiversity among the landscape units of MCM is controlled by airborne transport of organisms attached to sediment particles and overprints diversity caused by the contemporary differential growth and organisms. Microbial diversity from wide variety of microbial habitats in the MCM (soils, glacier ice, glacier sediments, cryoconites, airborne material, lake ice, lake mats, lake sediments and stream mats) was assessed using genomic techniques ranging from phenotypical fingerprinting to the use of high resolution genetic markers. Physical and chemical properties of each environment together with basic stoichiometry (C:N:P ratios) were also evaluated and used as an indicator of the physiological state of the organisms within each habitat. Aeolian sediment traps and acoustic wind erosion flux sensors were used to determine the timing, direction and magnitude of significant particle movement throughout Taylor Valley (TV). Our findings indicate that material in the TV is predominantly transported downvalley, i.e. from the Antarctic continent toward the McMurdo Sound during strong katabatic events when the wind speed is well above 10 m.s-1. The material transported via wind is physically and chemically similar to nearby soils. It is slightly alkaline (~ 8.6), has a very coarse texture (98% of particles > 250 μm), very low water content (< 2%) and organic matter content (<1%). Although it has a low organic content, owing the large amounts of material transported it is a significant source of C, N, P as well as microbial cells.

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