Taxonomic diversity and functional potential of microbial communities in oyster calcifying fluid

Previous research has underscored the influence of microbial metabolisms in carbonate deposition throughout the geological record. Despite the ecological importance of microbes to animals and inorganic carbon transformations, there have been limited studies characterizing the potential role of microbiomes in calcification by animals such as bivalves. Here, we use metagenomics to investigate the taxonomic diversity and functional potential of microbial communities in calcifying fluids from oysters collected at three different locations. We show a diverse microbial community that includes bacteria, archaea, and viruses, and we discuss their functional potential to influence calcifying fluid chemistry via reactions like sulfate reduction and denitrification. We also report the presence of carbonic anhydrase and urease, both of which are critical in microbial biofilm calcification. Our findings have broader implications in understanding what regulates calcifying fluid chemistry and consequentially the resilience of calcifying organisms to 21st century acidifying oceans.