Ocean Food Webs

Lesson Plan - Get It!

Audio:

All ecosystems have a food web.

• What is a food web?

A food web is an interlocking system of food chains that displays how energy is transferred between organisms in an ecosystem.

Food webs are made up of producers, consumers, and decomposers.

⇒ Producers are organisms that produce their own food.

⇒ Consumers are organisms that feed off other organisms.

Some consumers eat plants (herbivores), some eat meat (carnivores), and some eat both plants and meat (omnivores).

When looking at a food web, consumers are often divided into two groups: primary consumers and secondary consumers. Primary consumers are herbivores, and secondary consumers are carnivores and omnivores.

⇒ Decomposers are organisms that eat dead and decaying matter.

The image below shows an example of an ocean food web. Notice how the lines show which living organisms consume other living organisms.

• Which organisms are producers, and which are consumers?

• What is missing from this food web?

Decomposers are not always shown on a visual representation of food webs.

• What are some examples of marine decomposers?
• What role might they play in the food web shown above?

(If you are uncertain, check out the Elephango lesson in the right-hand sidebar under Additional Resources to find some examples of the ocean's decomposers.)

The energy transfer always moves in a cycle from producers to primary consumers, to secondary consumers, and finally to decomposers. This is a never-ending cycle.

The energy transfer always begins with the sun because sunlight is needed for plants to make their food during photosynthesis. All food webs start with producers.

• What organism is the start of all ocean food webs?

If you said phytoplankton, you are correct! Phytoplankton are the most basic form of plant life in the ocean and are responsible for about 50% of the oxygen in the earth's atmosphere.

Primary consumers, such as zooplankton and small fish, consume phytoplankton. Larger fish and sea creatures like squid eat the primary consumers. Finally, even larger secondary consumers, such as sharks, whales, and dolphins, consume these secondary consumers.

All dead and decaying animals are consumed by bacterioplankton, who are decomposers, and recycled back into the ocean as nutrients.

Watch the following video for a marine food web example. As you watch the video, list the producers, primary consumers, secondary consumers, and decomposers shown.

• What do you think would happen to this food web if one of the organisms shown became extinct?

Move to the Got It? section to practice creating your own ocean food web!