Aphotic zone
The aphotic zone is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1% of sunlight penetrates. Consequently, bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

 is essentially the only light found in this zone. Most food comes from dead organisms sinking to the bottom of the lake or ocean from overlying waters.

The depth of the aphotic zone can be greatly affected by such things as turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....

 and the season of the year. The aphotic zone underlies the photic zone
Photic zone
The photic zone or euphotic zone is the depth of the water in a lake or ocean that is exposed to sufficient sunlight for photosynthesis to occur...

, which is that portion of a lake or ocean directly affected by sunlight.

The ocean

Depending on how the zone is defined, the aphotic zone of the ocean begins between depths of roughly 200 m (656.2 ft) or 1000 m (3,280.8 ft), and extends to the ocean floor. Temperatures can range from roughly 0 °C (32 °F) to 6 °C (43 °F). Unusual and unique creatures dwell in this expanse of pitch black water, such as the gulper eel
Saccopharyngiformes is an order of unusual ray-finned fish superficially similar to eels, but with many internal differences. Most of the fish in this order are deep-sea types known from only a handful of specimens such as the Umbrella Mouth Gulper Eel. Saccopharyngiformes are also bioluminescent...

, the giant squid
Giant squid
The giant squid is a deep-ocean dwelling squid in the family Architeuthidae, represented by as many as eight species...

, the anglerfish
Anglerfishes are members of the teleost order Lophiiformes . They are bony fishes named for their characteristic mode of predation, wherein a fleshy growth from the fish's head acts as a lure; this is considered analogous to angling.Some anglerfishes are pelagic , while others are benthic...

, and the vampire squid
Vampire Squid
The vampire squid is a small, deep-sea cephalopod found throughout the temperate and tropical oceans of the world. Unique retractile sensory filaments justify the Vampire Squid's placement in its own order: Vampyromorphida , which shares similarities with both squid and octopuses...


The aphotic zone is further divided into additional zones: the bathyal zone, the abyssal zone, and the hadal zone. The bathyal zone extends from 200 metres (656 ft) to 2000 metres (6,562 ft). The abyssal zone extends from 2000 metres (6,562 ft) to 6000 metres (19,685 ft). The hadal zone spans from depths of 6000 metres (19,685 ft) to the ocean floor. Creatures in these areas must be able to live in complete darkness.

See also

  • Hadal zone
    Hadal zone
    The hadal zone , also known as the hadopelagic zone and trench zone, is the delineation for the deepest trenches in the ocean...

  • Abyssal zone
    Abyssal zone
    The abyssal zone is the abyssopelagic layer or pelagic zone that contains the very deep benthic communities near the bottom of oceans. "Abyss" derives from the Greek word ἄβυσσος, meaning bottomless. At depths of 4,000 to 6,000 metres , this zone remains in perpetual darkness and never receives...

  • Benthic zone
    Benthic zone
    The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos. They generally live in close relationship with the substrate bottom; many such...

  • Pelagic zone
    Pelagic zone
    Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...

  • Photic zone
    Photic zone
    The photic zone or euphotic zone is the depth of the water in a lake or ocean that is exposed to sufficient sunlight for photosynthesis to occur...

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