In the deep ocean, primary producers and their viruses are understudied relative to microbes in the surface ocean. This study is using cutting-edge techniques to identify key viral players and the processes by which they affect microbial carbon cycling in the dark ocean. It advances understanding of ocean biogeochemistry and meets national priorities in biotechnology and ocean exploration. The investigators are mentoring postdoctoral and undergraduate students and integrating their scientific findings into media products such as podcasts to share discoveries about “viruses in the wild” to inspire public interest in deep-sea exploration and microbial oceanography. In this project, the researchers are studying the biodiversity, mechanisms, and rates of virus-induced carbon cycling in a deep-sea hydrothermal vent system. While chemoautotrophic microbes are known to contribute to these hotspots of primary productivity, the functional role and biogeochemical impacts of viruses that infect them remain critical gaps in our understanding of the dark ocean’s carbon cycle. The researchers combine metagenomics with stable isotope probing (SIP) to identify links between metagenomic diversity and ecological function. They combine carbon-13 stable isotope probing (13C-SIP) with metagenomics, nanoscale secondary ion mass spectrometry (NanoSIMS), and microscopy to reveal the diversity, activity, mechanisms, and rate of virus-induced carbon cycling, and they use targeted sequencing of both