This is mostly within the photic zone, but includes parts of the aphotic zone where some plants will migrate seasonally or daily. Carnivorous nekton live partly at the surface but extend to water depths of several km searching for prey. Detritus feeders tend to occur in the aphotic zone out of range of the most active carnivores. Over half of the Earth's surface is deeper than 2 km below sea level. Bottom boundary layers in areas of strong currents can create 'benthic storms'.
Currents are variable in time and space.
There are some regions of quiet conditions. Substrate is normally mud except where manganese nodules form a hard pavement or on the slopes of active volcanoes. B. Deep Sea Life tends to decrease in biomass with depth and distance from shore. Crabs, brittle stars, starfish, sea urchins, sea cucumbers. Mostly bottom feeders and scavengers.