Chemosynthesis is a microbial process that utilize energy from chemical compounds to drive carbon fixation. In the ocean, it plays a significant role in converting inorganic compounds like CO2 into organic compounds, a process known as primary production. This process also helps mitigate climate change by sequestering CO2. The ocean serves as a substantial sink for greenhouse gases and for example, the Southern Ocean alone accounts for up to 40% of the oceanic uptake of anthropogenic CO2. However, this estimate only considers the CO2 sequestered via photosynthesis not chemosynthesis. Traditionally, primary production and CO2 sequestration in marine environments are attributed to photosynthesis. However, photosynthesis is limited by solar radiation, both temporally to daylight and spatially to the lit layers of the ocean (approximately 200m deep), which only account for 5% of its whole mass of water. In contrast, chemosynthesis can occur continuously across time and space if the appropriate energy sources are available, supporting ecosystems across the vast realms of the ocean through trophic and symbiotic interactions. Recent advancements suggest that chemosynthesis is likely the foundation of oceanic biogeochemistry and ecology, challenging the spotlight on photosynthesis as the key process sustaining marine ecosystems. Despite its importance, our understanding of the role of chemosynthesis in the ocean remains fragmented. For instance, its involvement in climate regulation has been overlooked and it is likely that this process plays a crucial role in buffering against climate change but is also vulnerable to its effects. Therefore, the overarching aim of this project is to use cutting-edge technologies such metagenomics, transcriptomics and isotope analysis to provide new insight into chemosynthesis mediators, CO2 sequestration and carbon budget in current and future climate scenarios.