Limited Bioweathering by Cyanobacteria in Cold, Nutrient-Limited Conditions: Implications for Microbe-Mineral Interactions and Aquatic Chemistry in Cold Environments

Abstract

Solute fluxes in Antarctic meltwaters indicate microbial processes influence chemical weathering. Antarctic cyanobacterial mats dominated by Leptolyngbya glacialis enhance weathering rates at 12 °C. Yet, their effects on nutrient fluxes in colder, nutrient-limited conditions, similar to the McMurdo Dry Valleys environments, are unknown. Here, we investigate biotic and abiotic weathering rates of glaciofluvial sediments at 4 °C and compare results to previous experiments at 12 °C. We also examine the effects of nutrient and salt concentrations on weathering fluxes by comparing the effects of different media concentrations (0.1X and 0.001X: 10 and 1000 times diluted) at both temperature conditions. Our results show limited evidence of biologically mediated silica release at 4 °C, yet microbe-mineral interactions still affect nutrient fluxes, particularly for Ca, Mg, Mn, P, and N. However, a higher initial salt concentration (0.1X media) increased the concentration of solutes released under abiotic conditions. These results indicate that aqueous solutes, temperature and microbial processes are all important factors controlling weathering rates and nutrient fluxes in cold settings.

Keywords:

• Antarctica
• cyanobacteria
• bioweathering
• chemical weathering, nutrient fluxes
• salt weathering

Acknowledgements

We thank Kristin Marra, Brenda Hall, and Alison Stumpf for sample collection; Nina D.S. Webb for her assistance in sample processing; Preston Larson for his help in SEM imaging; Andy E. Elwood Madden for his help in XRD data analysis; and Claire Curry for her help in statistical data analysis. We also thank Amy Callaghan, Boris Wavrick, Bradley S. Stevenson, Paul Lawson, and Anne Dunn for providing access to microbiology lab equipment and facilities. This project is funded by NSF grants #0842639, “Development of Quantitative Weathering Indicators in Proximal Alluvial Sediments to Assess Glacial Activity in the Rock Record’, and #1543344, “Quantifying Surface Area in Muds from the Antarctic Dry Valleys: Implications for Weathering in Glacial Systems.”

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Science Foundation