Prokaryotic Novelty and Metabolic Diversity in the Tagoro Shallow Hydrothermal System (Canary Islands, Spain).

The shallow hydrothermal system of the Tagoro submarine volcano (Canary Islands, Spain) has been discharging low-temperature, nutrient-rich, acidic fluids high in CO2 and H2S since March 2012. Despite influencing local microbial communities, the effects of these hydrothermal fluids on community structure and diversity across spatial gradients remain poorly understood. Using 16S rRNA gene sequencing, we observed significant differences in prokaryotic community structure from epipelagic waters to benthic habitats affected by hydrothermal activity. Prokaryotic richness and diversity decreased closer to hydrothermal sources, yet novel taxa were prevalent across all hydrothermally influenced habitats. Archaeal diversity was low and dominated by ammonia-oxidising Nitrosopumilaceae, while bacterial communities were more diverse, including iron-oxidising Mariprofundaceae, methane-oxidising Methylomonadaceae and metabolically versatile Rhodobacteraceae. Molecular analyses revealed microbial specialisation within these families, complementing scanning electron microscopy observations of active bacterial biomineralization in chimney fragments linked to Mariprofundaceae members. Together, these findings offer new insights into the ecology and functional potential of microbial assemblages in the Tagoro hydrothermal system, suggesting their involvement in nitrogen, iron, sulphur and methane cycling. This study advances our understanding of microbial distribution patterns in shallow-sea hydrothermal fields and highlights the high prevalence of novel taxa with potential biotechnological relevance.