Current warming in the Western Antarctic Peninsula (WAP) has multiple effects on the marine ecosystem, modifying the trophic web and the nutrient regime. In this study, the effect of decreased surface salinity on the marine microbial community as a consequence of freshening from nearby glaciers was investigated in Chile Bay, Greenwich Island, WAP. In the summer of 2016, samples were collected from glacier ice and transects along the bay for 16S rRNA gene sequencing, while in situ dilution experiments were conducted and analyzed using 16S rRNA gene sequencing and metatranscriptomic analysis. The results reveal that certain common seawater genera, such as Polaribacter, Pseudoalteromonas and HTCC2207, responded positively to decreased salinity in both the bay transect and experiments. The relative abundance of these bacteria slightly decreased, but their functional activity was maintained and increased the over time in the dilution experiments. However, while ice bacteria, such as Flavobacterium and Polaromonas, tolerated the increased salinity after mixing with seawater, their gene expression decreased considerably. We suggest that these bacterial taxa could be defined as sentinels of freshening events in the Antarctic coastal system. Furthermore, these results suggest that a significant portion of the microbial community is resilient and can adapt to disturbances, such as freshening due to the warming effect of climate change in Antarctica.

Hydrogen peroxide (H₂O₂) has been shown to efficiently remove toxic microalgae from enclosed ballast waters and brackish lakes. In this study, in vitro experiments were conducted to assess the side effects of mitigating toxic and non-toxic dinoflagellates with H₂O₂. Five H₂O₂ concentrations (50 to 1000 ppm) were used to control the cell abundances of the toxic dinoflagellates Alexandrium catenella and Karenia selliformis and the non-toxic dinoflagellates Lepidodinium chlorophorum and Prorocentrum micans. Photosynthetic efficiency and staining dye measurements showed the high efficiency of H₂O₂ for mitigating all dinoflagellate species at only 50 ppm. In a bioassay carried out to test cytotoxicity using the cell line RTgill-W1, control experiments (only H₂O₂) showed cytotoxicity in a concentration- and time- (0 to 24 h) dependent manner. The toxic dinoflagellates, especially K. selliformis, showed basal cytotoxicity that increased with the application of hydrogen peroxide. Unexpectedly, the application of a low H₂O₂ concentration increased toxicity, even when mitigating non-toxic dinoflagellates. This study suggests that the fatty acid composition of toxic and non-toxic dinoflagellate species can yield toxic aldehyde cocktails after lipoperoxidation with H₂O₂ that can persist in water for days with different half-lives. Further studies are needed to understand the role of lipoperoxidation products as acute mediators of disease and death in aquatic environments.

Infections in confined environments can spread by direct contact, contaminated surfaces, and airborne transmission. This is critical in prison facilities, where cleaning and sanitary conditions are inadequate. An alternative is the development of antimicrobial surfaces. A new antimicrobial coating was developed by incorporating copper microparticles into a standard commercial paint, aiming to reduce the concentration of bacteria on surfaces by granting antimicrobial properties to surfaces. The copper additive comprised Cu₂Cl(OH)₃ deposited on polyhedral zeolite. The efficacy of this coating was evaluated in detention cells in a police station, which are temporary prisons and inherently dirty environments. The experiment compared a cell painted with the copper additive coating and a control cell with the standard paint. Viable coliforms were measured on different surfaces and in the air for five months under normal usage. Bacterial load was reduced by ca. 68% by the copper-amended paint on cement surfaces. Surprisingly, airborne viable coliforms were reduced by ca. 87% in the detention cell treated with the copper coating. This research highlights the potential of antimicrobial coatings in controlling the spread of infections through contact with contaminated surfaces and emphasizes the significant reduction in airborne bacterial load. It is especially relevant for controlling infections where sanitization is limited but can be extended to other built environments, such as healthcare facilities.