Diversity and structure of the deep-sea sponge microbiome in the equatorial Atlantic Ocean
Sponges (phylum Porifera) harbour specific microbial communities that drive the ecology and evolution of the host. Understanding the structure and dynamics of these communities is emerging as a primary focus in marine microbial ecology research. Much of the work to date has focused on sponges from warm and shallow coastal waters, while sponges from the deep ocean remain less well-studied. Here, we present a metataxonomic analysis of the microbial consortia associated with 23 deep-sea sponges. We identify a high abundance of archaea relative to bacteria across these communities, with certain sponge microbiomes comprising more than 90% archaea. Specifically, the archaeal family Nitrosopumilaceae are prolific, comprising over 99% of all archaeal reads. Our analysis revealed sponge microbial communities mirror the host sponge phylogeny, indicating a key role for host taxonomy in defining microbiome composition. Our work confirms the contribution of both evolutionary and environmental processes to the composition of microbial communities in deep-sea sponges. ImportanceThe deep ocean is the largest biome on Earth, accounting for >90% of the planets marine environment. Despite this it remains a largely unexplored ecosystem, with less than 0.01% of the deep seafloor having been quantitatively sampled. Deep-sea sponges are ancient metazoans which harbour complex microbial communities and much still remains to be learned about the composition and diversity of these unique microbiomes. In an effort to address this, here we report a metataxonomic analysis of the microbial consortia associated with 23 deep-sea sponges from the equatorial Atlantic Ocean. Our findings reveal intricate, species-specific microbial communities dominated by ammonia-oxidizing archaea. This study highlights the significant role sponges play in shaping microbial consortia, providing new insights into deep-sea ecosystem dynamics. Importantly, our findings provide a scientific basis for understanding the evolutionary relationships between sponges and their symbiotic microorganisms.