bathyal zone; midnight zone; bathypelagic zone
Oceanographic term for the depth zone roughly 200–4,000 meters, where sunlight does not penetrate. Used in scientific and educational contexts.
Many bioluminescent organisms live in the bathyal zone.
This deep-sea fish is commonly found in the midnight zone.
深海帯 (abyssal zone) refers to deeper ocean layers, typically below 4,000 meters, while 漸深海帯 covers the middle depth range.
表層帯 (epipelagic zone) is the sunlit surface layer, contrasting with the dark 漸深海帯.
Compound of 漸 (gradual, approaching) + 深海 (deep sea) + 帯 (zone), literally 'zone approaching the deep sea'. The term is a calque from Western oceanographic classification.