Name: ______
The Ocean Deep
Layers of the Sea
Read about the five layers of the ocean and then answer the questions below.
Scientists have divided the ocean into five main layers. These layers, known as "zones", extend from the surface to the ocean depths where light can no longer penetrate.
Sunlight Zone (surface-200 meters): The top layer of the ocean is called the sunlight zone. It is known as the sunlight zone because this top layer gets most of the light.
Twilight Zone 200-1000 meters): The light that reaches the twilight zone is very faint. It is in this zone that we begin to see the twinkling lights of bioluminescent creatures.
Midnight Zone (1000-4000 meters): No sunlight reaches this zone. Here the only light is that made by the creatures themselves. The water pressure at this depth is incredible, but even so, a large number of creatures can be found here. Sperm whales can dive down to this level in search of food.
Abyssal Zone (4000-6000 meters): This layer is also called the abyss. The water temperature is near freezing, and there is no light at all. Very few creatures can be found at these crushing depths. Most of these are invertebrates such as basket stars and tiny squids. Most of the ocean floor is in this zone.
Deep Trench (6000 to deepest parts): The last layer goes to the deepest parts of the ocean, mostly in deep water trenches and canyons. Life can still be found here. Starfish and tube worms can thrive at these depths.
1. On a blank piece of paper, draw a diagram of the 5 layers of the ocean. Label each layer. Include the depth of each layer.
2. The ______layer has the most light.
3. In the ______layer the light from the sun is very faint, but it has the greatest variety of strange fish (including bioluminescent ones).
4. The light in the midnight zone comes from ______.
5. List two kinds of creatures that live in the abyssal zone.
6. ______and ______can both live in the deepest trenches.
Monsters of the Deep
Go to and select a deep-sea creature. Then answer questions 7 – 10.
7. Common name of your creature: ______
8. Depth it lives at: ______
9. Describe your creature:
10. What is the coolest fact that you read about your creature?
Deep Sea Bioluminescence
Deep in the ocean, where sunlight can’t reach, is a world of darkness. Here, creatures make their own light, called bioluminescence. They do this by mixing chemicals in their bodies. This is just like a firefly, and similar to green light sticks.
These creatures produce light for many reasons. For some, it is a warning to stay away. For others, it is a form of camouflage. Some creatures use their light for navigation. Certain fish species use bioluminescence as a form of "night light". Some use it for communication. Other creatures use bioluminescence as a trap. The anglerfish uses a lighted "lure" on the top of its head to attract its prey. Whatever the reason for producing this dazzling light show, it remains as one of the natural world's most spectacular displays.
11. What is bioluminescence? Give an example.
12. List 5 different reasons why fish produce light.