Regional consistency in microbial community responses to hydrocarbon pollution in maritime Antarctic soils.

Antarctica, though remote and sparsely inhabited, faces significant ecological risks due to human activities and settlements that generate, among others, fuel leaks. In particular, maritime ice-free soils are becoming increasingly vulnerable to environmental disturbances, particularly hydrocarbon (HC) contamination, which represents a significant ecological threat. Low temperatures and limited nutrients reduce microbial degradation rates, allowing contamination to persist for decades. Despite their ecological importance, the structure and environmental drivers of Antarctic soil microbial communities under chronic HC exposure, such as at research stations, remain poorly understood. In this study, we characterized the bacterial/archaeal and eukaryotic communities across 106 soils sampled near research stations in three regions of the Antarctic Peninsula and the South Shetland Islands over two consecutive years, encompassing a wide range of HC pollution levels. Using 16S and 18S rRNA gene sequencing, we assessed amplicon sequence variants (ASVs) and explored spatial and environmental variables that influence microbial diversity, structure, and functional potential. While bacterial/archaeal beta-diversity was primarily influenced by geographic distance, functional profiles and eukaryotic diversity were shaped mainly by environmental factors, particularly HC concentration, pH, and conductivity. We identified consistent shifts in community composition, with HC and conductivity negatively correlated with alpha-diversity, and pH positively correlated. Hydrocarbon pollution consistently reduced microbial alpha-diversity and enriched specific taxa and functions. Notably, an Actinobacterium (Williamsia) and a Leotiomycetes fungus, largely dominated in heavily polluted sites. These taxa emerged as consistent indicators – or sentinel taxa – of HC pollution at a regional scale. Microbial communities in Antarctic soils are shaped differently by a dynamic interplay between space and environment, but chronic pollution can drive consistent community shifts across geographically distant sites.