Phytoplankton

Now that I have discussed some of the biggest animals in the ocean, I will now talk about the smallest. The basis of the ocean's food chain is phytoplankton. The term phytoplankton refers to thousands of species of tiny plants and algae that live in the ocean. Phytoplankton work like other plants, turning sunlight and carbon dioxide into energy and oxygen. The phytoplankton in the ocean are responsible for over 50% of all oxygen in our atmosphere.

Phytoplankton comes in many shapes and sizes and all are microscopic. Any time you swim in the ocean, you are immersed in a soup of living plants. Murkier water tends to have more abundant plankton where clear water has very little.

Phytoplankton are the first step in most food chains in the ocean. Tiny animals called zooplankton eat phytoplankton. Larger animals eat zooplankton, and bigger fish and animals eat them. Many larger animals eat just phytoplankton as well. Whale sharks, the biggest fish in the world, eat nothing but phytoplankton.