Marine Ecosystems

In the Marine Ecosystem is where we will find our oceans and where we will find marine life and plants.

The marine ecosystem covers most of the earth’s surface and there are millions of different plants and animals in the marine ecosystem.


There are five oceans around the world; Arctic, Atlantic, Indian, Pacific and Southern oceans and they all have water.

These oceans cover over 70% of the earths surface and one of the deepest oceans, Mariana Trench is as deep as Mt. Everest is tall.

In the ocean and the saltwater bays, in seas and in inlets, there are small organisms and bacteria that help make up part of the creatures that live in the Marine Ecosystem.

Ocean Zones

There are three zones in the ocean, the euphotic zone, this zone gets the most sunlight, the disphotic zone, this zone gets some sunlight but not enough for plants to survive and the third zone, the aphotic zone, gets no sunlight at all.

Marine Life

Plant life in the ocean gets food from photosynthesis so the top zone is the only zone that has plants.

These plants include seaweed, sea grasses and algae. Kelp is one plant that is known to grow in the ocean.

Marine Animals

Plankton and other fish are found in the ocean. Plankton is a huge source of food to marine life.

There are other animals such as fish, walruses, whales, bacteria, seals, dolphins and so many more. There are animals found in the ocean that even make their own light.

The ocean is so big that no one is sure that all the animals in the ocean have been discovered and new discoveries are happening all the time.

Since the ocean gets super deep, most of the animals live in the top 200 meters of the water and the ocean that is deep is very dark and there is very little food.

Facts About the Marine Ecosystem:

  • Crabs, fish and other animals live in salt marshes.
  • Living things, such as ocean animals are able to live in salt and in soil.
  • Salt marshes are wetlands that contain special plants and animals.
  • When rivers flow into oceans, fresh water can mix with salt water and this is where salt marshes form.
  • There are over 200,000 different kinds of marine life that have been discovered.
  • The largest animal is the Blue Whale.
  • The longest fish is the Whale Shark.
  • The fastest fish is the Sailfish.
  • Coral is an animal and it builds on hard skeleton around itself to be protected. It is only the size of an ant.

What Did You Learn?

  • How many oceans are there around the world? There are five different oceans around the world, the Atlantic, Pacific, Indian, Arctic and Southern Oceans.
  • What kind of animals live in the ocean? All kinds of different animals such as fish, plankton, whales, shark and many other animals live in the ocean.
  • What happens when river freshwater and ocean saltwater mix? When this happens, a salt marsh is formed.
  • How many zones are there in the ocean? There are three zones and the top one gets light, the middle one gets a little light and the lower one gets no light at all.
  • Can plants live in the middle or lower zones of the ocean? Plants cannot live in these zones because they need light to make photosynthesis.