Mercury (Hg) is a global contaminant that impacts ecosystems worldwide. This session invites contributions that advance our understanding of the biogeochemical cycling of mercury across terrestrial, freshwater, coastal, and marine ecosystems by targeting key biotic and abiotic processes (e.g., microbial (de)methylation, partitioning, uptake) and sources (e.g., erosional runoff, atmospheric deposition, or industrial contamination). We welcome field, laboratory, and modeling studies that consider mercury biogeochemical processes, especially in response to disturbances (e.g., permafrost thaw, wildfire, glacial retreat, sea level rise, eutrophication) and/or co-occurring stressors (e.g., selenium, invasive species, microplastics). Emphasis is placed on interdisciplinary studies that leverage one or more emerging tools in mercury biogeochemistry, such as meta-omics sequencing (e.g., microbial genomics and transcriptomics), natural abundance stable isotopes, or atomic-level speciation techniques (e.g., X-ray absorption spectroscopy), to generate new mechanistic insights and advance predictive understanding of mercury behavior in the environment.