Hypoxia and the microbiome: Significance and application for ecotoxicological studies

Hypoxia, or low oxygen availability, is a growing environmental concern that significantly impacts microbial communities. Recent studies highlight the effects of hypoxia on microbial composition and function, favoring anaerobic taxa involved in nitrogen, sulfur, and carbon cycling. These shifts influence ecotoxicological processes by modulating pollutant degradation, metal bioavailability, and greenhouse gas emissions. For instance, oxygen depletion enhances the activity of anaerobic dechlorinators but may reduce heavy metal detoxification. Advances in metagenomics and multi-omics have offered new perspectives on microbial adaptation under hypoxic stress, revealing key metabolic pathways linked to pollutant transformation. However, knowledge gaps remain in our understanding of the long-term ecological consequences of hypoxia-induced microbiome shifts. This review synthesizes recent findings on hypoxia-microbiome interactions, focusing on both environmental (e.g., sediment and water column) and host-associated (e.g., gut) microbiomes, and emphasizes their application in ecotoxicology. In addition, we discuss how hypoxia-induced microbial shifts in hypoxic environments and highlight potential applications of microbiome-based approaches for environmental risk assessment. Future research integrating experimental and modeling approaches is crucial to better predict the ecological impacts of hypoxia-driven microbial changes in contaminated environments.