||The region of the water column that is generally in contact with the abyssal seafloor,
except in deep basins and trenches and represents the bottom layer of the ocean, generally
from 4,000 meters to 6,000 meters depth. This layer is aphotic; it receives biogenic,
detrital and mineral material descending from above and this layer acts as an accumulation
zone. Oozes from tests of planktonic organisms form on the seafloor and fans of sedimentary
material accumulate here. There are diverse and specialized faunal communities at
these depths. Trophic webs are based on chemoautotrophic processes, hydrothermal vents,
decomposition of organic matter and bacterial production.