Abyssal Zone: Definition & Examples

Instructor: Amanda Robb
This lesson is about the abyssal zone, a deep layer near the bottom of the ocean. In this lesson we will cover what the abyssal zone is, and examples of different ecosystems in the abyssal zone.

What is the Abyssal Zone?

Picture the deepest, darkest part of the ocean. Fish that glow in the dark, gigantic sea worms, and explosive, hydrothermal vents. This creepy scene is the abyssal zone. The abyssal zone is the deepest layer of the ocean near the sea floor - it starts at 13,000 feet and goes to about 20,000 feet.

This layer of the ocean is incredibly deep and does not get any sunlight from the surface. The communities are encased in perpetual darkness, and the temperatures are also cold, hovering near freezing, due to the lack of sunlight. In addition, due to the amount of water covering the abyssal zone, the pressure is extreme, between 200 and 600 times that of the surface. Despite these challenges, organisms have evolved to inhabit this environment, which will be discussed in further detail below.

Layers of the Ocean

To understand the abyssal zone, we need to get an idea of what the other layers of the ocean look like. The surface of the ocean down to about 200 feet is called the epipelagic zone. This is where sunlight penetrates the water and where a wide variety of sea life exist. Following the epipelagic zone is the mesopelagic zone, where sunlight is very faint and you begin to find creatures that glow in the dark, or are bioluminescent.

After the mesopelagic zone is the bathypelagic zone, or the midnight zone. This water is entirely dark and has extreme pressure, despite the abundance of sea life. After these layers is the abyssal zone, the focus of this lesson. The only layer deeper than the abyssal zone is the hadalpelagic zone, which occurs from the sea floor into the deepest trenches, or vertical caverns, in the ocean. Below is a diagram of the ocean layers.

The ocean zones, with abyssal zone near the sea floor.
ocean zones

Abyssal Zone Ecosystems

Despite the extreme conditions in the abyssal zone, some organisms manage to inhabit this ecosystem. No green plants can survive in this environment, since there is no sunlight with which to make energy. Instead, chemosynthetic organisms use chemicals from hydrothermal vents to create energy. These bacteria are food for large tube worms that also inhabit the vents. The tube worms and bacteria can then support crustaceans, like crabs. Tube worms living in the deep sea vents are shown below.

Tube worms living in hydrothermal vents
tube worms

Fish also exist at these depths. One example is the deep sea anglerfish, which uses a light attached to the end of its head to attract prey, as shown below. Many organisms use bioluminescence, lighting up to attract prey and navigate the darkness.

Deep sea anglerfish live in the abyssal zone.
anglerfish

The tripod fish has three projections that allow it to rest on the ocean floor, scanning for prey.

Tripod fish
tripod fish

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