Did you know that 70% of the Earth's surface is covered by the ocean? This makes the ocean the Earth's largest ecosystem!

What is an ecosystem? An ecosystem is made up of all living and nonliving things in an area. In the ocean, this includes all plants and animals as well as water, rocks, and sand!

You're welcome! Thank you for protecting me from the scary smaller fish!

Thank you for protecting us from the big and scary fish!

In the ocean's ecosystem many organisms depend on each other to survive. Take a look at these clown fish. See how they are hiding in this sea anemone? The sea anemone protects the clown fish from predators. In return, the sea anemone is protected by the clown fish from small fish that would try to harm it. Relationships like this one where both organisms benefit from one another is called mutualism. 

I give the coral important nutrients they need to survive!

I protect the algae from predators and help them get plenty of sunlight!

Look, there's a piece of coral that is helping out algae by protecting it from predators. As the algae grows on the coral, the algae give the coral important nutrients that they need to survive. Organisms big and small help protect each other in the ocean. These relationships are important as one cannot survive without the other. 

Thank you for protecting us from predators and giving us your leftovers!

You're welcome! Thank you for keeping those pesky parasites off me! 

Mutualism can be found all throughout the ocean's ecosystem! Here, these pilot fish are helping keep this shark healthy by removing parasites from the shark's body. In return, the shark protects the pilot fish from dangerous predators who wish to eat them. The pilot fish are also able to get their food from the shark's leftovers.