Biofilms on glacial surfaces: hotspots for biological activity

Area of Science:

• Glaciology
• Microbiology
• Biogeochemistry

Background:

• Glaciers play a crucial role in Earth's hydrological and carbon cycles.
• Warming trends predict increased glacial melt, affecting nutrient transport to aquatic ecosystems.
• Microbial activity on glaciers, particularly cryoconite, influences albedo and melt, but this was previously unstudied in Antarctica.

Purpose of the Study:

• To investigate microbial community structure and function on Antarctic glacial surfaces.
• To determine if microbial communities form biofilms on Antarctic glacial sediments.
• To assess nutrient cycling and organic matter accumulation within these biofilms.

Main Methods:

• Confocal laser scanning microscopy (CLSM) was used to visualize microbial communities.
• Nanoscale secondary ion mass spectrometry (NanoSIMS) was employed to analyze isotopic enrichment (¹³C and ¹⁵N).
• Incubation experiments with labeled isotopes (¹³C-NaHCO₃ and ¹⁵NH₄) assessed nutrient transfer.

Main Results:

• Microbial communities on Antarctic glaciers were found to form biofilms, covering approximately 35% of cryoconite sediment surfaces.
• Significant enrichment of ¹³C and ¹⁵N was observed in *Bacteroidetes* and *Oscillatoria* (cyanobacteria) when incubated with labeled carbon and ammonium.
• Nutrient transfer from cyanobacteria to heterotrophic bacteria was dependent on their spatial proximity within the biofilm.

Conclusions:

• Microbial biofilms are a key feature of Antarctic glacial surfaces, influencing nutrient cycling.
• The spatial organization of microbes within biofilms facilitates efficient nutrient transfer and organic matter accumulation.
• Biofilm formation on cryoconite minerals can impact glacier surface albedo, potentially exacerbating melt.