Deep-sea ecology is the scientific discipline dedicated to studying the interactions between organisms and their environment in the deep ocean, typically defined as waters below the euphotic zone. This field investigates the unique biodiversity, physiological and ecological adaptations to extreme conditions (such as high pressure, low temperature, and aphotic environments), and the structure and function of deep-sea ecosystems, including those reliant on chemosynthesis. Its significance stems from its focus on Earth's largest biome, its contribution to understanding global biogeochemical cycles, and the discovery of novel biological and geological processes.