Airborne organic pollutants impact microbial communities in temperate and Antarctic seawaters.

Airborne Organic Pollutants (AOPs) reach remote oceanic regions after long range atmospheric transport and deposition, incorporating into natural microbial communities. This study investigated the effects of AOPs on natural microbial communities of the Mediterranean Sea, the Atlantic Ocean and the Bellingshausen Sea, by assessing the impact of both non-polar and polar AOPs on cell abundances, chlorophyll a concentrations and cell viabilities of different microbial groups. Our results indicate that almost all groups, except flagellates in the Bellingshausen Sea, were significantly affected by AOPs. While no significant differences in chlorophyll a concentrations were observed between non-polar and polar AOPs, significant variations in cell abundances were noted. Cell death occurred at AOP concentrations as low as five times the oceanic field levels, likely due to their high chemical activity. Cyanobacteria in temperate waters exhibited the highest sensitivity to AOPs, whereas medium and larger diatoms in the Bellingshausen Sea were more affected than smaller diatoms or flagellates, contrary to the expected size-related sensitivity trend. Additionally, microorganisms in temperate waters were more sensitive to the polar fraction of AOPs compared to the non-polar fraction, which showed an inverse sensitivity pattern. This differential sensitivity is attributed to variations in the ratio of polar to non-polar AOPs in the respective environments. Our findings underscore the varying impacts of AOPs on marine microbial communities across different oceanic regions.