Ocean Food Chain

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

This lesson is on ocean food chains. In this lesson, we'll go over what a food chain is and what the different oceans are. Then, we'll get into two specific food chains in the Arctic and Pacific Ocean.

A Hidden World

On the surface, the ocean is a solid blue or grey color depending where you are. There are white crests of waves that dot the surface, but otherwise it looks pretty uniform, right? This is true, but under the surface, there is a whole world of life that looks like nothing else! Thick jungles of colorful coral are actually animals, hosting slews of other species, like flowing sea anemones, tropical fish, and herds of deadly sea snakes.

Belcher sea snake in Australia.
Sea snake

But, this beautiful world isn't isolated to the tropics! Even in water temperatures near freezing in the Arctic, schools of fish, seals and polar bears form an ecosystem like none other. Today, we're going to dive into the oceans head first by taking a look at these ecosystems through the lens of a food chain.

A mother harp seal nurses her pup in the Arctic.
harp seals

What Is a Food Chain

A food chain is a diagram showing the linear transfer of energy between different species. Since the energy is transferred as food, a food chain basically shows what eats what in an ecosystem. Food chains are organized into different levels called trophic levels. The bottom trophic level is made of producers, or organisms that make their own food. Vegetarians, called herbivores or primary consumers, eat the producers. Secondary consumers are carnivores that eat the primary consumers. Tertiary consumers are top predators in the food chain, eating both primary and secondary consumers.

Trophic levels in a food chain
food chain

What Are Our Oceans?

Oceans are large bodies of salt water that cover nearly 70% of the Earth's surface. There are five oceans, the Atlantic, Pacific, Arctic, Indian and Southern. Oceans are home to abundant sea life and are important in regulating global temperatures and providing food and water for humans. Today, we'll look at the food chains for two oceans, the Arctic and the Pacific.

Food Chain of the Arctic Ocean

The Arctic Ocean is a frigid, harsh environment. It is located in the north-most part of the globe. The surface is frozen over with large chunks of sea ice year round.

Sea ice over the Arctic Ocean
sea ice

Below, the water is near freezing. Despite these challenges, life abounds in the Arctic. The producers in the Arctic Ocean are phytoplankton, microscopic organisms that make their own food. Other microscopic creatures, such as zooplankton feed on the phytoplankton. Small fish also feed on phytoplankton. Secondary consumers eat the fish, such as narwhals, seals and larger fish. The tertiary consumers in this food chain are the orca whale and the polar bear. These top predators prefer seals, but will eat fish and even larger prey, such as other whales. Orca whales have been known to take down gray whales, mammoth animals reaching 45 feet in length and up to 80,000 pounds!

As a tertiary consumer, orca whales eat seals
killer whale

Food Chain of the Pacific Ocean

The Pacific Ocean ranges from the Arctic Ocean all the way to the Southern Ocean and between Asia and the Americas. Since the Pacific Ocean is the largest ocean in the world, it has a diverse climate. Northern and Southern areas of the Pacific can be quite cold, although areas near the equator are tropical, with temperatures reaching a warm 70 degrees. Here, let's look at one of the most fascinating food chains in the Pacific Ocean, the Great Barrier Reef. As the largest reef in the world, the Great Barrier Reef is home to immense biodiversity off of the coast of Australia.

A satellite view of the Great Barrier Reef
Great Barrier Reef

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