Snow albedo, an important feedback in climate change, is strongly decreased by the growth of snow algae such as Chlamydomonas nivalis. Snow algae are very successful in low nutrient snow environments globally, where they can reach concentrations of over one million cells per ml snow melt. Snow algae growing on the Greenland Ice Sheet have been shown to decrease albedo by one third to one half, and recent work has called for the inclusion of this effect in numerical albedo models. In order to understand the conditions leading to snow algae blooms and subsequent impacts on albedo, we must determine how algae thrive in challenging, low nutrient environments. Snow algae blooms are more common in snow containing large amounts of dust, and in these systems, minerals are commonly observed attached to snow algae cell walls. These observations suggest that minerals play a role in meeting the nutrient needs of snow algae. To test this hypothesis, we are performing field and laboratory studies. We have examined the mineral phases present in the snow algae phycosphere of samples dominated by Chloromonas rostafinskii, collected from Mt. Anderson, CA, using synchrotron X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), and X-Ray Absorption Near Edge Structure (XANES) analyses. Synchrotron measurements revealed the presence of poorly crystalline Fe oxyhydroxide precipitates similar to ferrihydrite associated with the algal biomass, as well as a few crystalline ferrous phases. Our synchrotron measurements of the dust in the snow not associated with the algae indicated largely crystalline primary minerals with no ferrihydrite-like phases detected. To better understand the snow algae-microbe-mineral interactions, we are growing xenic snow algae cultures under Fe-limiting conditions with Fe-containing minerals. The snow algae cultures grew better in the presence of olivine than without olivine present. In addition, a secondary Fe-containing phase formed in the presence of the snow algae culture with olivine that did not form in the sterile olivine-containing control. Our future research will work to interpret the mechanisms by which snow algae growth is enhanced in the presence of minerals, how minerals are formed in the presence of snow algae, and the implications for climate change and the detection and interpretation of potential mineralogical biosignatures of life on Earth and other planetary bodies.

Interactions of snow algae, microorganisms, and minerals in snowpack: Implications for Earth’s albedo and potential biosignature formation

253rd National Meeting (2017)

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