The profundal zone is often part of the aphotic zone.
2.
Very few invertebrates are able to inhabit the cold, dark, and oxygen poor profundal zone.
3.
The demersal zone is just above the benthic zone and forms a layer of the larger profundal zone.
4.
The decomposition of organic materials can continue in the benthic and profundal zones if the matter falls through the water column before being completely digested by the pelagic bacteria.
5.
The "'profundal zone "'is a deep zone of an inland body of freestanding water, such as a lake or pond, located below the range of effective light penetration.