Title

Bioavailability of Mineral-Bound Iron to a Snow Algae-Bacteria Co-Culture and Implications for Albedo-Altering Snow Algae Blooms

Document Type

Article

Abstract

Snow algae can form large-scale blooms across the snowpack surface and near-surface environments. These pigmented blooms can decrease snow albedo, increase local melt rates, and may impact the global heat budget and water cycle. Yet, underlying causes for the geospatial occurrence of these blooms remain unconstrained. One possible factor contributing to snow algae blooms is the presence of mineral dust as a micronutrient source. We investigated the bioavailability of iron (Fe) -bearing minerals, including forsterite (Fo90, Mg1.8Fe0.2SiO4), goethite, smectite and pyrite as Fe sources for a Chloromonas brevispina – bacteria co-culture through laboratory-based experimentation. Fo90was capable of stimulating snow algal growth and increased the algal growth rate in otherwise Fe-depleted co-cultures. Fo90-bearing systems also exhibited a decrease in bacteria:algae ratios compared to Fe-depleted conditions, suggesting a shift in microbial community structure. The C. brevispina co-culture also increased the rate of Fo90 dissolution relative to an abiotic control. Analysis of 16S rRNA genes in the co-culture identified Gammaproteobacteria, Betaprotoeobacteria and Sphingobacteria, all of which are commonly found in snow and ice environments. Archaea were not detected. Collimonas and Pseudomonas, which are known to enhance mineral weathering rates, comprised two of the top eight (> 1 %) OTUs. These data provide unequivocal evidence that mineral dust can support elevated snow algae growth under otherwise Fe-depleted growth conditions, and that snow algae can enhance mineral dissolution under these conditions.

Keywords

Algal-bacterial coculture; Chloromonas brevispina; Forsterite; Iron bioavailability; Mineral weathering; Pedobacter; Snow algae

Disciplines

Earth Sciences | Life Sciences

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