Beyond the Reef: Ocean Layers

As we leave the shorelines and the shallow water habitats of coral reefs, mangroves and intertidal zones, the ocean changes its physical (light (photic), temperature and pressure) as well as biological and ecological characteristics.

Within the deep ocean there are 5 specific interconnected vertical layers:

Epipelagic or Photic Layer: found within the upper 200 meters of the ocean, found here are the primary producers such as plankton that maintain enough sunlight to photosynthesize forming the bottom layer of the food web.

Mesopelagic or Mesophotic – between 200 and 1000m the primary producers are replaced with sinking organic matter as the primary food source including plankton. Down at these depths the consumers are often scavengers finding nutrition in the organic matter or sunken carcasses from larger marine animals. In the deeper part, between 500-1000m up to 95% of all deep-water fish species are found and 65% of decapod (Crab, shrimp, lobster) are found. Many species create bioluminescence, a special chemical reaction that creates a light source.

ocean layers
Image created by Ben Eliason

Bathypelagic: its dark and cold down here between 1000 and 4000 meters, but even still there is much life, the marine organisms are adapted to high pressures of ocean water and often have small eyes, the ability to bio luminesce and are dark in colour. Food for these animals is often the sinking organic matter (snow). Hydrothermal vents are located within the bathypelagic area.

Abyssopelagic: between 4,000 to 6,000 meters, and at extreme water pressures and low temperatures, species diversity is greatly reduced. The primary organisms on the sea floor include the decapods (shrimp, lobster and crabs) The floor is a find mud sediment on these largely flat plains, found at these depths can be the sea mounts rising towards the ocean surfaces as well as hydrothermal vents. Dead carcasses from whales are often the main form of food for those animals that dwell here.

However, we still have further to travel, there is one more layer left:

The Hadal Layer: the deepest, darkest and coldest of all ocean layers, found below 6,000 meters. The world’s deepest known treasures: the Marianas and Tongan trenches lay far under the ocean’s surface. These bottom habitats are covered in a fine mud and marine organisms are sparse, finding small communities residing around fallen carcasses and dead matter.


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