Habitats
In oceanic environments, benthic habitats can be further zoned by depth. From the shallowest to the deepest are: the epipelagic (less than 200 meters), the mesopelagic (200–1,000 metres), the bathyal (1,000–4,000 meters), the abyssal (4,000–6,000 meters) and the deepest, the hadal (below 6,000 meters).
The lower zones are in deep, pressurized areas of the ocean. Because of the high pressures and seclusion neither tidal changes nor human impacts have had much of an effect on these areas, and the habitats have not changed much over the years. Many benthic organisms have retained their historic evolutionary characteristics. Some organisms are significantly larger than their relatives living in shallower zones, largely because of higher oxygen concentration in deep water.
It is not easy to map or observe these organisms and their habitats, and most observation has been done through remote controlled submarines.
Read more about this topic: Benthic Zone