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Producers in the Oceans, Kinds of Plant Plankton

A food chain or web shows how energy moves from one group of living things to another. Think of a mouse. A mouse gets the energy it needs from eating grass and seeds. If the mouse is eaten by a snake, its energy moves up the food chain to the snake.

The starting points in any food chain or web are the living things that make their own food. These are called producers. On land, green plants are the main producers.

Food Chains and Webs All the trees and other plants in this forest are made from water, sunlight and a small part of the air.

Green plants make their own food. This process is called photosynthesis. To do this, they need sunlight, the gas carbon dioxide, and water. With the energy from sunlight, plants can combine water and carbon dioxide to make glucose (sugars). The sugars are the plant's food.

Food Chains and Webs


Plants are the world's largest living things. Sequoia trees are probably the largest of the plants. The biggest of these trees is nearly 275 feet (84 meters) tall. It weighs more than 2,000 tons (2,032 tonnes).

Food Chains and Webs Seaweeds are not always green, like land plants. They can be red, or brown like this kelp.

Producers in the Oceans

In the ocean, there are no green plants to make food. Seaweeds such as kelp are one ocean producer. The ocean's main producers are plankton. Plankton are simple creatures that float on ocean currents. They can be plants, animals, or bacteria. Plant plankton is called phytoplankton.

Phytoplankton make food through photosynthesis, like green plants. And like green plants, they need sunlight to make food. So phytoplankton are found close to the ocean surface.

Although tiny, phytoplankton make more food than land plants. Two-thirds of all the photosynthesis on Earth is due to phytoplankton.


Food Chains and Webs Where ocean conditions are right, phytoplankton do well. There can be billions of phytoplankton in a bucketful of water. When there are so many of them, they turn the water green, brown, or red.

Kinds of Plant Plankton

There are many kinds of phytoplankton. The most common are diatoms, blue-green algae, and dinoflagellates.


Food Chains and Webs Diatom skeletons can have many different shapes. There are round diatoms that look like doughnuts. Some diatoms look like long boats. Other diatoms look like snowflakes. There are even diatoms that have three corners. They look like pirate hats.

Diatoms have beautiful clear skeletons. They look as if they are made of glass. They are the most common plankton in cooler seas. Blue-green algae are actually a bacteria. They join together in long strings, sheets, or hollow balls. Large numbers of them can turn the sea blue-green.

Food Chains and Webs Blue-green algae are the oldest of all living things. There have been blue-green algae on Earth for over 3500 million years.

Dinoflagellates are found in tropical waters. They are common around coral reefs. They are also found in freshwater. All dinoflagellates have a long, whiplike “tail.” This is called a flagella. Whipping it from side to side, they move through the water.

Additional topics

Science Encyclopedia for KidsFood Chains and Webs