In a previous blog, we talked about the depth of the ocean Since the ocean is on average 3 miles deep, it may not surprise you that the water column is not uniform. In fact, sections of the water column in the ocean are differentiated by pressure, light, temperature, oxygen and mineral nutrients. It is because of these elements that certain sections of the ocean only contain certain marine animals. In this blog, we will explore the layers of the ocean and what types of marine life resides in those layers.

The ocean water column is made up of 5 zones. The sunlight zone, the twilight zone, the midnight zone, the abyss and the trenches.

Sunlight Zone

This zone extends from the surface down to about 700 feet. This is where most of the visible light is and with light comes heat. This is where the wide range of temperatures occur. Most marine animals live in this zone and feed off of photoplankton (the basis of the ocean food chain) and smaller fish. Photoplankton is responsible for almost half of the earth’s oxygen released in the atmosphere.

Twilight Zone

This zone extends from 700 feet down to about 3,280 feet. The light that reaches this zone is pretty faint. Larger fish like, whales and giant squid dive to these depths to feed. It is in this region that we start to see bioluminescent fish and all sorts of bizarre looking fish.

The Midnight Zone

This zone extends from 3,280 feet to 13,125 feet. In this zone, the only visible light is produced by the fish themselves. The water pressure at this depth is immense at 5,850 pounds per square inch. Despite the intense pressure, a large number of creatures can be found here. Sperm whales can dive to this level to feed and the color of animals that live in this zone are either black or red due to lack of light.

The Abyssal Zone

This next zone extends from 13, 125 feet down to 19,690 feet. The water temperature here is near freezing, at 32 degrees Fahrenheit and there is no light at all. Very few creatures can be found at these crushing depths. These creatures are invertebrates like basket star fish and tiny squid. Seventy-five percent of the ocean floor lies in this zone.

The Trenches

This zone extends from 19,690 down to the deepest parts of the ocean, which extend down to about 35,797 feet. The temperature is around freezing and the pressure is an amazing eight tons per square inch. That is approximately the weight of 48 Boeing 747 airplanes. Despite the temperature and pressure, life can still be found here. In fact, the deepest part of the ocean where life was found was 27,460 ft.

In future blogs, we will continue to learn more about our oceans, which make up two-thirds of our earth.

(Pictures courtesy: