Data Sheet 1_Hydrogeological compartmentalization outweighs hydrochemistry in structuring microbial communities across contrasting subsurface habitats.zip

Well identity explained a substantially larger fraction of community variation than hydrochemistry, indicating strong hydrogeological compartmentalization. PDL supported a larger recurrent bacterial component, stronger taxon–environment relationships, and repeated methanogen-associated archaeal signatures, whereas SF contained a smaller persistent community fraction and a greater contribution from localized taxa. Across both systems, Acetobacterium was the dominant bacterial genus and was largely represented by a single recurrent lineage distributed across multiple wells and hydrochemically distinct habitats.

Recurrent taxa in PDL were enriched in anaerobic and sulfur-associated lineages, while SF was characterized by a smaller set of persistent groundwater-associated taxa. Methanogen-associated archaea were largely restricted to PDL and included both methylotrophic and hydrogenotrophic lineages. These results demonstrate that hydrogeological compartmentalization outweighs hydrochemistry in structuring microbial communities across contrasting subsurface habitats.

The persistence of recurrent bacterial lineages, together with localized archaeal assemblages, suggests that deep groundwater ecosystems are shaped by the combined effects of hydrogeological compartmentalization, environmental filtering, and adaptation to long-term energy limitation.</p>