Aphotic

The Dark Ocean

In the ocean, the aphotic zone is sometimes referred to as the dark ocean. Depending on how it is defined, the aphotic zone of the ocean begins between depths of about 200 m (660 ft) to 800 m (2,600 ft) and extends to the ocean floor. The majority of the ocean is aphotic, with the average depth of the sea being 4,267 m (13,999 ft) deep; the deepest part of the sea, the Challenger Deep in the Mariana Trench, is about 11,000 m (36,000 ft) deep. The depth at which the aphotic zone begins in the ocean depends on many factors. In clear, tropical water sunlight can penetrate deeper and so the aphotic zone starts at greater depths. Around the poles, the angle of the sunlight means it does not penetrate as deeply so the aphotic zone is shallower. If the water is turbid, suspended material can block light from penetrating, resulting in a shallower aphotic zone. Temperatures can range from roughly 0 °C (32 °F) to 6 °C (43 °F).