Abstract

Deep-sea ecosystems have transitioned from being perceived as biological deserts and geochemically inactive to being recognized as major players in regulating Earth's biogeochemical cycles and long-term carbon storage. They include various ocean-floor environments, such as abyssal plains, hydrothermal vents, cold seeps, seamounts, and hadal trenches, each with its own microbial and faunal communities that promote nutrient cycling and organic matter decomposition. The process of deep-ocean carbon storage is multistep. It includes the sinking of particulate organic carbon from surface waters, microbial carbon fixation, and burial of the organic material in sediments over geological timescales. Recent research has shown that deep-sea inhabitants are actively involved in nutrient remineralization, methane oxidation, and the stabilization of carbon-rich compounds, thereby influencing global climate dynamics. Nevertheless, the security of these processes is put at risk by trawling, mining, plastic pollution, and changes in ocean chemistry associated with warming. As human activities push into deeper oceans, gaining a thorough understanding of biological interactions, sediment processes, and carbon fluxes is essential. This review compiles existing knowledge of deep-sea ecosystem services, identifies uncertainties in carbon budget calculations, and suggests the need for improved monitoring using autonomous observation systems and high-resolution modeling. The preservation of deep-sea areas is hence a key factor not only for supporting biodiversity but also for maintaining their crucial role in regulating Earth's climate.

Keywords: Deep-Sea ecosystems, Biogeochemical cycles, Carbon sequestration, Sediment processes, Marine microbial communities, Climate regulation, Anthropogenic impacts