A reconnaissance study of microbial community variation along a lithium-enriched watershed

Projected global lithium (Li) demand for net-zero transitions calls for innovative approaches for subsurface mineral exploration and environmental monitoring. In this study, we conduct a reconnaissance-scale assessment exploring environmental DNA-based microbial profiling to evaluate preliminary associations between microbial communities and Li in freshwater systems. In a survey along the Magaguadavic River (New Brunswick, Canada), we integrated 16 S rRNA metabarcoding of stream sediment and water samples with geochemical analyses, complemented by publicly available glacial till data. Microbial community composition varied most strongly across sites characterized by differing Li concentrations in surrounding till, consistent with watershed-scale geochemical gradients influencing community structure. Sediment communities showed greater compositional shifts than aqueous ones, reflecting physicochemical complexity and dynamic exchange with overlying waters-both influenced by Li inputs from glacial till. These inputs, governed by slow mineral weathering and rapid surface reactions, may modulate Li exposure and Li bioavailability across timescales. We observed restructuring of dominant taxa along Li gradients, with some responding consistently across environments and others showing environment-specific patterns, suggesting distinct ecological niches or exposure pathways. These results document preliminary, community-level patterns in a Li-enriched freshwater catchment and highlight the feasibility of using microbial data as a complementary tool in future, hypothesis-driven studies.