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aphotic zone
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Diagram showing ocean zonation by depth and region, with labeled layers: littoral, sublittoral, bathyal, abyssal, and hadal along the seafloor, and epipelagic, mesopelagic, bathypelagic, and abyssalpelagic in open water. The littoral zone is at the high-tide mark. Vertical scale marks photic and aphotic zones from surface to 10,000 meters.
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aphotic zone

oceanography
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Diagram showing ocean zonation by depth and region, with labeled layers: littoral, sublittoral, bathyal, abyssal, and hadal along the seafloor, and epipelagic, mesopelagic, bathypelagic, and abyssalpelagic in open water. The littoral zone is at the high-tide mark. Vertical scale marks photic and aphotic zones from surface to 10,000 meters.
Zonation of the ocean. The open ocean, the pelagic zone, includes all marine waters throughout the globe beyond the continental shelf, as well as the benthic, or bottom, environment on the ocean floor. Nutrient concentrations are low in most areas of the open ocean, and as a result this great expanse of water contains only a small percentage of all marine organisms. Far below the surface in the midocean ridges of the abyssal zone, deep-sea hydrothermal vents supporting an unusual assemblage of organisms—including chemoautotrophic bacteria—occur.

The aphotic zone is the region of the ocean that receives too little sunlight for photosynthesis to occur. This zone lies beneath the photic zone, which is the surface layer where sunlight penetrates. The aphotic zone encompasses the majority of the ocean's waters and is characterized by perpetual darkness. Within this zone, nutrient salts are abundant due to decomposed biological materials settling from upper layers, but the lack of sunlight prevents their uptake by photosynthesis. Organisms in the aphotic zone are adapted to high pressure, darkness, and calm waters. Some marine life inhabits this zone permanently, while others migrate to the photic zone nightly.1234

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6 Britannica Sources
  1. photic zone
  2. aphotic
  3. marine ecosystem - Geography, oceanography, and topography
  4. aphytal zone
  5. abyssal zone
  6. bathypelagic zone

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