Until now few studies have explored the microbiomes of glass sponges (Hexactinellida). Vazella pourtalesii forms globally unique, monospecific sponge grounds under low-oxygen conditions on the Scotian Shelf. Using metagenomic binning we performed detailed analyses of the metabolic functional capacities of four V. pourtalesii-associated microbial taxa (SAR324, Patescibacteria, Nanoarchaeota, and Crenarchaeota).