Cold-water coral reefs are known to locally enhance the diversity of deep-sea fauna as well as of microbes. Sponges areamong the most diverse faunal groups in these ecosystems, and many of them host large abundances of microbes in theirtissues. In this study, twelve sponge species from three cold-water coral reefs off Norway were investigated for therelationship between sponge phylogenetic classification (species and family level), as well as sponge type (high versus lowmicrobial abundance), and the diversity of sponge-associated bacterial communities, taking also geographic location andwater depth into account. Community analysis by Automated Ribosomal Intergenic Spacer Analysis (ARISA) showed that asmany as 345 (79%) of the 437 different bacterial operational taxonomic units (OTUs) detected in the dataset were sharedbetween sponges and sediments, while only 70 (16%) appeared purely sponge-associated. Furthermore, changes inbacterial community structure were significantly related to sponge species (63% of explained community variation), spongefamily (52%) or sponge type (30%), whereas mesoscale geographic distances and water depth showed comparatively smalleffects (,5% each). In addition, a highly significant, positive relationship between bacterial community dissimilarity andsponge phylogenetic distance was observed within the ancient family of the Geodiidae. Overall, the high diversity ofsponges in cold-water coral reefs, combined with the observed sponge-related variation in bacterial community structure,support the idea that sponges represent heterogeneous, yet structured microbial habitats that contribute significantly toenhancing bacterial diversity in deep-sea ecosystems.
2013. Vol. 8, no e55505