The deep ocean, where water depth exceeds 1,000 m (hydrostatic pressure greater than 10 MPa), covers 90% of the ocean's area and harbors the largest biosphere on Earth. It also serves as a significant reservoir of heat and greenhouse gases, absorbing over 90% of thermal surplus and 40% of anthropogenic CO₂, thereby mitigating the effect of global warming. High hydrostatic pressure (HHP) is a universal parameter shared by all the deep-ocean ecosystems, while its influence on biogeochemical cycling remains insufficiently investigated due to technical challenges. To address the research needs, we developed a platform of oceanic environment simulation and in-situ experimental equipment including Deep Ocean Experimental Simulator (DOES) with real-time optical and electrochemical monitors, In-Situ Fixation Sampler (ISFS), Ocean Automatic Series Incubation System (OASIS). These technologies enable in-depth investigation into the regulatory mechanisms of HHP on microbial carbon and nitrogen cycling. It reveals that HHP decreases the mineralization efficiency of labile organic carbon and increases that of refractory organic carbon, thus regulating the release of greenhouse gases such as CH₄ and CO₂ and the carbon cycle in the deep ocean(Li et al., 2023; Lin et al., 2025; Lv et al., 2022; Yang et al., 2020). Additionally, co-occurrence of anaerobic and aerobic oxidation of organic carbon coupling with stimulated microbial denitrification under HHP, making deep ocean a hotspot of nitrogen loss and enhancing the release of greenhouse gas N₂O(Yang et al., 2024). These finding challenge certain traditional perspectives and suggest a reassessment of the marine carbon and nitrogen cycling.
 

environmental simulation technology,in situ test technology,deep ocean,hydrostatic pressure,carbon and nitrogen cycling