Name: ______________________________
The Ocean Deep
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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
Name: ______________________________
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 http://www.seasky.org/monsters/sea7a1.html 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.
Name: ______________________________
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.