Which aquatic zone receives less than 1% of sunlight?
The aphotic zone lies below the depth at which usable sunlight can support net photosynthesis. In many aquatic classifications, its upper boundary occurs where irradiance has fallen to about 1% of the value at the surface, although the exact depth changes with water clarity, season, and solar angle. Suspended sediments, dissolved organic matter, and plankton absorb or scatter light, so turbid lakes become aphotic at shallower depths than clear oceans. Because photosynthetic production is negligible there, organisms depend mainly on organic particles sinking from illuminated layers, dissolved o
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 2-3