I should have said "not much lives below 1000m until you get to the ocean floor". Not much can happen in the deep ocean because light doesn't penetrate that deeply. The creatures that do live there have to rely on organic material falling slowly from the surface.

The [Bathypelagic Zone] is also marked by very low temperatures (5 or 6 degrees Celsius) and having a very low organismal biomass, a trend that will continue until reaching the ocean floor.

From this article