The aphotic zone is primarily found in the oceanic biome, particularly in the deep sea regions. This zone extends from a depth where sunlight can no longer penetrate, typically starting around 200 meters (656 feet) below the ocean’s surface. In this dark environment, photosynthesis is not possible, and the ecosystem relies on organic material that sinks from the lighted zones above, usually referred to as the photic zone.
The aphotic zone is characterized by extreme conditions, including high pressure, low temperatures, and complete darkness. As a result, the organisms that inhabit this zone have unique adaptations to survive the harsh environment, such as bioluminescence and specialized feeding mechanisms to capitalize on the scarce resources.
In addition to the oceanic biome, smaller aphotic zones can be found in some large freshwater bodies where light does not reach the bottom. However, when we think of the vast and complex ecosystems associated with aphotic conditions, the oceanic biome is the most significant example.