Soil microbial carbon and nitrogen transformations at a glacial foreland on Anvers Island, Antarctic Peninsula

Microbial communities can play a critical role in soil development and succession at glacial forelands through their contribution to soil carbon (C) and nitrogen (N) cycling. Using a combination of molecular fingerprinting techniques and metabolic rate measurements, we examined the soil microbial community composition and key transformations in the C and N cycles at a glacial foreland on Anvers Island along the Antarctic Peninsula. Soils were sampled along transects representing a chronosequence of < 1 to approximately 10 years since deglaciation. The soil microbial community was active adjacent to the receding edge of the glacier, where soil had been ice-free for < 1 year. A survey of the microbial community composition identified typical soil bacterial species such as Arthrobacter and Sphingomonas, as well as known Antarctic heterotrophs, cyanobacteria and fungi. The soil C cycle over this zone was dominated by phototrophic microbial activity, while the N cycle was dominated by heterotrophic N-2-fixation and not cyanobacterial N-2-fixation as found at other recently deglaciated forelands. Other N transformations such as ammonia oxidation and denitrification appeared to be of limited relevance.