Antibiotic resistance genes in seawater and sediments along the Antarctic Peninsula

The spread of antibiotic resistance genes (ARGs) poses a significant risk to public health and ecosystem stability. The marine environment acts as a natural reservoir for ARGs and receives wildlife and human-derived discharges, influencing their persistence and dissemination. Due to its minimal human impact, Antarctica serves as a valuable model for examining the "pre-antibiotic" resistome and the effects of anthropogenic activity on antimicrobial resistance. This study investigated the abundance and distribution of bla_TEM, sul1, and tetW genes, as well as microbial populations (16S rRNA), across 17 stations in the Antarctic Peninsula (62°S-67°S). Bacterial DNA from seawater and marine sediments was analysed by qPCR and correlated with geography and depth. 16S rRNA gene sequencing also assessed evidence of faecal contamination. Baseline absolute abundances of ARGs ranged from 2.1 to 3.3 log GC per litre (seawater) or gram (sediment). Relative abundances (log ARG/16S) ranged from -5.3 to -6.7. These values represent the mean ranges observed across both seawater and sediment samples. TetW was detected in all water samples and sul1 in all sediments, indicating a consistent, matrix-specific distribution. ARGs were four orders of magnitude higher in areas affected by human activity and wildlife. Faecal contamination detected near scientific bases indicates wastewater discharges as a potential source of ARGs. These results provide a quantitative baseline for Antarctic marine ARGs, highlight the sensitivity of polar systems to localized human and wildlife impacts, and position the Southern Ocean as a sentinel environment for ARG monitoring.