Oceanography- Food Chain

• Science
• Age 5

The Ocean’s Food Chain

The Ocean’s Food Web

By: Chelsea Davis

Food Web: 

A food web is all of the food chains that exist in a single ecosystem. It shows how energy flows through an ecosystem.

An example of a food chain within the ocean is…

A crab eats ocean worms

A pufferfish eats the crab

A shark eats the pufferfish

What do you already know about a food web?

What do all living things need energy to do….

1. Run, Swim, Walk, Sleep
2. Eat Ice Cream Sundae’s
3. None of The Above
4. Live and Grow!

Consumers: Eat other animals to receive their energy.

(Photosynthesis)

Producers: Make up their own energy.

Trophic Levels

Food webs help us realize changes in the ecosystem.

- Removing a predator or nutrient can greatly effect other species of a food web. These effects can be indirect or direct.

- What’s a direct effect? A effect that immediately impacts a species in the food web. 

- What’s an indirect effect? when direct effects move throughout the food web causing impacts to one or more connected species

What is a real life example of a direct or indirect effect?

Trophic levels are individual levels that define where the organism fits into the food web.

- Producers (plants & algae) are at the base of the food web

- Primary consumers eat producers

- Secondary consumers eat the primary consumers 

- Tertiary consumers eat the secondary consumers

Producers

Primary

Secondary Consumers

Tertiary Consumers

Producers: 

- They make their own food through photosynthesis and chemosynthesis

What is photosynthesis? Thee process plants, algae, and some bacteria use to convert sunlight, water, and carbon dioxide into their own food (sugars) and oxygen.

What is chemosynthesis? the process by which organisms, like certain bacteria, use energy from inorganic chemical reactions to produce food, rather than using sunlight

Fun Facts: 

- Phytoplankton are responsible for more than half of the oxygen in our atmosphere, which is a byproduct of photosynthesis.

-In some cases, massive blooms of certain phytoplankton can cause "red tides" or "dead zones" when they die, leading to marine life suffocation or poisoning due to the release of toxins and depletion of oxygen. 

(Algae, Phytoplankton, Bacteria)

- Also known as autotrophs

- In coastal regions of the ocean, algae, such as kelps and rockweeds, and plants, such as sea grasses, are important primary producers

Fun Facts:

-Many primary consumers have internal bacteria that help them digest cellulose, a tough substance in plant cell walls.

- Many large animals are primary consumers that filter feed. Examples include baleen whales, which consume vast amounts of zooplankton and krill, and some sea turtles and manatees, which graze on seagrass and algae.

Primary Consumers:

- Zooplankton, snails, fish, reptiles and mammals. 

- They only eat plants and phytoplankton. 

- All herbivores are primary consumers that eat from the base of the food chain

Herbivores:

Carnivores:

- eat other carnivores are at least tertiary consumers because they feed on secondary consumers or consumers at a higher trophic level.

- All carnivores are considered predators, which have to attract or hunt their prey to eat.

-In the marine environment, apex predators tend to travel large distances across the ocean throughout their lives while tracking prey.

Omnivores:

- Omnivores eat both plants and animals. While omnivores are usually secondary consumers, they can act as prey, predators, and sometimes scavengers.

- Some common aquatic omnivores include snails, sea turtles, zooplankton, and crabs. 

How do changes in a food web impact the other species in it?

- Entire food webs can be changed by the population of one type of predator or prey within the food web.

- If there was a depletion of one type of prey, a predator may switch to eating more of another prey species to meet their needs and this is called a direct effect. 

- When a top preditor is taken away from the food web it allows an increase in prey and this indirectly affects animals lower on the food chain that are then eaten more by the growing number of organisms and this is called trophic cascade and it affects animals across multiple trophic levels.

What are some key takeaway’s from today’s lesson?

What are some key terms to remember?

Reference Slide:

National Oceanic and Atmospheric Administration. Aquatic Food Webs. 18 Nov. 2025, https://www.noaa.gov/education/resource-collections/marine-life/aquatic-food-webs.