At equilibrium, the export flux of organic material sinking into the aphotic zone is balanced by the upward flux of nitrate.
12.
Hydrothermal vents are the primary source of energy in what is known as the aphotic zone ( depths exceeding 200 m ).
13.
In the ocean, this leads to a vertical separation of nitrification from primary production, and confines it to the aphotic zone.
14.
In general, the deep sea is considered to start at the aphotic zone, the point where sunlight loses its power of transference through the water.
15.
This leads to the situation whereby any nitrate in the water column must be from the aphotic zone, and must have originated from organic material transported there by sinking.
16.
Some, such as the " swallowers ", can live as deep as 3, 000 m ( 10, 000 feet ) in the ocean, well into the aphotic zone.
17.
Additionally, it is suggested that fluorescent tissues that surround an organism s eyes are used to convert blue light from the photic zone or green bioluminescence in the aphotic zone into red light to aid vision.
18.
The fraction of primary production that is exported to the aphotic zone is generally higher when primary production occurs in short ( seasonal ) bursts, than when it occurs more evenly spread out across a year.
19.
Being just above the ocean floor, the demersal zone is variable in depth and can be part of the photic zone where light can penetrate and photosynthetic organisms grow, or the aphotic zone, which begins between depths of roughly and extends to the ocean depths, where no light penetrates.
