Understanding Our Ocean’s Food Chain For Kids

The ocean is such a vast place that it has a very complex food chain. A food chain is a system of organizing living creatures into different levels. Each level is dependent on the organisms below as their food sources. Sometimes when issues such as oil spills or overfishing occur, it can destroy entire populations of fish or other species. In this way, the predators of those creatures (including humans!) are directly affected, since they now have less food to eat. With less food, the predators can go hungry and fall ill or die. On the other hand, the prey of those same creatures may flourish since they are not being eaten, and then start overpopulating. Even this is actually a bad thing, since overpopulation can cause several other problems. As you can see, the ocean food chain consists of a very delicate balance. If something goes wrong, it creates a domino effect and several other creature populations are affected in turn. The marine food chain is divided into the four categories outlined below. Let’s read on to explore how life under the ocean works!

Level 4: Large Predators

The most powerful and strongest creatures exist at the top-most level of the ocean’s food chain. The ocean-dwellers in this category are creatures like whales, sharks, and dolphins. Semi-aquatic mammals that live on land but spend plenty of time in the water for feeding include polar bears, sea lions, seals, and walruses. All of these creatures are at the highest level of the ocean food chain because they are bigger or faster than other creatures.

Level 3: Meat-Eating Creatures

The next level usually has other creatures that mostly feed on small fish. Some of these are fish themselves, but they tend to be bigger, like sardines and herring. There are also cephalopods, which are creatures like squid, octopuses, and cuttlefish. The large fish in this category eat small fish from the next level. The cephalopods might eat small fish, as well as shelled creatures like shrimp and lobsters.

Level 2: Herbivores

Herbivores are creatures that consume plants for their food. In the ocean, there are many plants like seaweed and kelp. There are two kinds of herbivores in the ocean. One kind includes creatures like parrotfish, manatees, and turtles. The second kind of herbivores are a bit smaller and include tiny fish, krill, jellyfish, scallops, and clams. These creatures enjoy eating ocean plants as well as other organic material that drifts in the water.

Level 1: Ocean Plants and Microscopic Organisms

At the very base of the food chain are a collection of plants and very tiny organisms called phytoplankton. They may seem quite insignificant, but their purpose is quite the opposite. The entire food chain depends on these plants and phytoplankton. They help to transform the sun’s light into energy and nutritious substances that keep the other fish healthy. Without them, the ocean’s food chain would be extremely disrupted, and it could take a very long time to recover!




Level 4

Fast, large, powerful creatures that prey on fish from levels 3 and 4.

Whales, dolphins, tuna, barracuda, polar bears, walruses, seagulls, penguins, pelicans.

Level 3

Large fish and cephalopods. They may use physical size, or features such as tentacles to obtain prey.

Snappers, herring, cuttlefish, squid, octopuses.

Level 2

Smaller creatures that feed on plant matter and phytoplankton.

Manatees, turtles, jellyfish, shrimp, krill, sea urchins, starfish, clams.

Level 1

Plants and passive single-celled creatures. They require sunlight and minerals in the water to thrive.

Kelp, seaweed, algae, phytoplankton.

Remember that there are always exceptions to these rules. For example, while many sea stars normally feed on drifting matter or decomposing fish, there are some sea stars that actually eat snails and even oysters! On the other hand, polar bears might eat creatures from their own level, like seals, as well as fish from the level below. Can you think of other examples of creatures in the food chain that cross the typical boundaries of their level? After reviewing the following resources, think about what you and others could do to help preserve life in the ocean.