Modeling Marine Food Webs and Human Impacts Overview In this two-part lesson, students will develop food webs and investigate human impacts on marine ecosystems. In Part I, students will explore the ecological role of organisms in an ocean habitat and use information provided on Food Web Cards to develop food chains. In Part ll, students will model the interconnected feeding relationships in the open ocean ecosystem by developing food webs and then use their food webs to explore the impact that different scenarios have on the ecosystem.

Grade Levels: 5-8 Learning Objectives Students will be able to: • Analyze the role of organisms as producers, consumers, and decomposers in marine ecosystems. • Develop a model to describe the movement of energy in marine ecosystems. • Use their model to explore impact scenarios in marine ecosystems. NGSS Performance Expectations • 5-LS2-1: Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment. • MS-LS2-3: Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.

Suggested Time: Two 50-minute class periods Materials • Student Worksheet 1 • Student Worksheet 2 • Poster paper for creating food webs • Markers in multiple colors • Food Web Cards • Food Chain image • Food Chain with Energy Flow Arrows image • Sample Completed Food Web • For the teacher – Computer with Internet access, projector 1 Media Resources • Blue Whale Barrel Roll video • The Tucker Trawl video • Endangered Sea Turtles video • Marine Debris Impacts video

Part I: Food Chains in the Open Ocean

Students will explore the roles that different organisms play in a marine ecosystem by determining the links that exist between the organisms. Engage • Ask students: o Can anyone tell me why we eat? You are looking for answers that connect food and eating with needing energy to grow and survive.

o How about animals in the ocean—what kinds of things do you think that they eat?

Let students share their prior knowledge and ideas about what creatures in the ocean eat. If they say animals or plants, prompt them to go into more detail or description.

• Tell students: Now we will watch a video showing one kind of ocean animal—a blue whale— eating. Prompt them to look for the following as they watch: o What does the whale eat? o How do scientists learn about what, and how, whales eat? • Play video: Blue Whale Barrel Roll (see box) In this video, students will see how an animal of such enormous size feeds on masses of small, shrimp-like krill (zooplankton), obtaining enough to eat.

Interested in a closer look at how scientists “tag” whales to track their behavior in the ocean? Watch Tagging a Humpback Whale.

• After viewing the video, discuss with students: o What did you observe the whale eating in this video? o How much krill does a blue whale eat? o Do you think krill are important?

2 o What do you think these krill eat? o How do you think scientists know what whales, fish, and other animals in the ocean eat? Explore • Tell students: Now we are going to watch a short video that will give you a glimpse into how scientists learn about the kinds of food that are in the ocean for marine life to eat. It shows scientists using a system of nets to take samples of small marine organisms at different levels in the water. Let’s see what they find. • Play video: The Tucker Trawl • After viewing the video, ask students: o What kinds of organisms did the trawl bring up? o What did they look like? How big were they? o What animals in the ocean eat these organisms? Explain • Tell students: Who eats whom in an ecosystem can be represented by a food chain. • Download and project this Food Chain image of a sample food chain from a grassy field ecosystem. Then, download and project this Food Chain with Energy Flow Arrows image to show the flow of energy as organisms in the ecosystem eat one another. • “Read” this food chain out loud, creating a concrete meaning for the arrows with your students: Grass is eaten by the grasshopper, which is eaten by the mouse, which is eaten by the owl. The energy flows from the grass to the grasshopper, to the mouse, to the owl. • Explain that a food chain, such as the one shown here, shows the series of steps in which energy, and matter, flow through organisms in an ecosystem as one organism gets eaten by another. The main takeaway: The arrows in a food chain show the flow of energy through the food chain. Follow the arrows to move ”up” the food chain. • Ask students: What role does the Sun play in this food chain? Explain that the Sun is the primary source of energy, which gets transferred through organisms in the food chain in this grassy field and all other ecosystems on land. The Sun is also the primary source of energy for life in the regions of the ocean where sunlight penetrates. • Tell students: Now you are going to build your own food chains to show the feeding relation- ships between some of the creatures that live in the ocean. • Organize students into teams of two to four. • Distribute: Every student should get Student Worksheet 1, and each team should get a set of Food Web Cards.

3 • Give the following directions: Have each team explore the Marine Life Cards. Using the information about diet provided on the cards, challenge teams to build at least five different food chains. They should link as many organisms together in a chain as they can—but use at least two in each one. Tell them that an organism may have relationships with more than one other organism in the stack of Food Web Cards; there is not one right answer. Have students capture their work in Student Worksheet 1. • Call on a few teams to share their food chains with the class. Which team made the most food chains? Which team(s) made the longest chain? • Ask students: o What pattern do you observe when you look at all these different food chains? Sample answers: They all begin with phytoplankton; larger animals eat smaller animals; phytoplankton and zooplankton are the smallest organisms in the chains.

o Can animals be in more than one food chain? Are there certain animals that are in more food chains than others? Elaborate • Tell students: Each creature in the food chain has a role in the ecosystem. Write the terms “producer,” “consumer,” and “decomposer” on the board. Discuss the words and what they mean. Definitions: o Producers (or primary producer) can make their own food, converting inorganic compounds into energy-rich organic compounds, usually through photosynthesis. o Consumers obtain energy and nutrients by eating other organisms, which can be plants or other animals; all consumers are animals. o Decomposers obtain energy from dead organisms, breaking down the organic matter and returning the raw material (such as carbon, nitrogen, and phosphorus) to the ecosystem. • Ask students: o Looking at the food chains that you built, who are the producers?

Answer: the phytoplankton, which get energy from the sun through photosynthesis

o Name some consumers in your ocean food chains. Sample answers include: krill, tuna, sharks

• Optional extension: If you would like to go into further detail about feeding levels in a food chain, bring in that learning goal here. Explain to students that each step in a food chain is a different feeding level, like steps up a ladder. Primary producers always make up the first level,

4 followed by primary consumers, secondary consumers, and so on up the food chain. For example, the mouse in the example food chain above is a secondary consumer. The top consumer on a food chain is called an apex predator. Apex predators have few, if any, natural predators of their own. • Point out that as energy flows through an ecosystem “up” through the food chain, matter (such as carbon and oxygen) is recycled at every feeding level. For example, as an animal eats, it takes in from the food what it needs for body repair, growth, and other biological processes and releases the rest as waste. The organic matter in the waste, and in the animal itself when it dies, is broken down into inorganic substances and returned to the environment by decomposers. • Explain that although decomposers (such as bacteria) may not be visible or immediately apparent in an ecosystem, they are there and play a role that is just as important as that of the consumer. Emphasize that decomposers act on all organisms in the food chain: they break down the wastes of living organisms and the organic matter of dead organisms at every feeding level and cycle the nutrients back into the environment, making them available again for primary producers and consumers in the ecosystem. • Discuss the role of phytoplankton as the primary producers in the ecosystem. Explain that, sim- ilar to the role that plants play on land, these tiny photosynthetic organisms convert the Sun’s energy and nutrients into compounds that go on to feed other organisms in the ecosystem, ei- ther directly or indirectly. Point out that all food chains in the ocean begin with phytoplankton or algae, which are consumed directly by zooplankton. The zooplankton are then consumed by other larger animals, including the largest animal to have ever lived on Earth—the blue whale. Evaluate • Direct students to Student Worksheet 1 to study the food chains they drew. Have them apply their understanding of the roles of producers, consumers, and decomposers by labeling the roles of the creatures in their food chains.

Part 2: Food Webs

Although food chains are useful for showing feeding connections, an ecosystem consists of more complex interactions. In this part of the lesson, students will connect their chains together to build a model of these interactions, known as a food web. Building Food Webs Explore • Tell students: Now you will use the food chains that you made to build a model—called a food web—that shows the interconnected feeding relationships and energy flow in an ecosystem.

5 • Give teams poster paper on which they can create their food webs. Direct students to lay out their Food Web Cards on the poster paper and connect the organisms with arrows according to the food chains they determined in Part I. Suggest to students that they rearrange the cards as needed and that they start building their food webs with producers and consumers. • Optional: Have students label each organism with its role in the ecosystem— primary producer, primary consumer, secondary consumer, or tertiary consumer. They may choose to use differ- ent colors for the arrows to represent the different feeding levels. • Finally, have students lay down their Decomposers card and draw arrows to convey how, ultimately, the matter from all of the organisms in the food web is cycled back into the environment. Explain • Have teams share their posters and discuss as a class the numerous overlapping relationships seen in the webs. • Ask students: What observations can you make about the food web you have just modeled? Guide students to realize that many feeding interactions exist within an ecosystem and that one organism is often connected to many other organisms. • Have students copy the food web from their posters onto Student Worksheet 2. • Use the Sample Completed Food Web provided to assess students’ food webs, circling where on their food webs they need to make edits. Using Food Webs to Explore Human Impacts to Ecosystems Now that students have built food webs showing how food and energy are connected in an ecosystem, they can use these models to understand how a disturbance to one organism in the web affects other organisms, and how human activities have the potential to affect many organisms in marine ecosystems. Students will gather evidence from two short videos and make predictions using the food web that they built. • Tell students: Food webs can be used as models to study the effects of changes to an ecosystem. Tell students that as an example, they will explore how sea turtles are being impacted by humans. • Play videos: Endangered Sea Turtles; Marine Debris Impacts • Ask students: o What are some things that are hurting sea turtles?

Answers include accidental capture in nets (bycatch), predation, loss of nesting beaches due to irresponsible development, marine debris, and poaching.

o Which of these are caused by human activities?

6 Answers include getting caught in finishing nets, habitat destruction, poaching, and marine debris.

• Now, have students consider that the leatherback sea turtles in the ocean became severely threatened due to bycatch of thousands of sea Only about turtles in trawl nets each year and to the destruction of beaches where 1 percent of leatherbacks migrate to lay eggs. Also, propose that the problem is sea turtles further compounded by the increasing presence of marine debris, such survive to as plastic bags, in the ocean. The leatherback sea turtles think that plastic adulthood! bags in the water look like their favorite food—jellyfish—and eat them. • Explain to students that because a food web is composed of many different interconnected relationships between species, changes that affect one species often have cascading effects on others in the ecosystem. • Demonstrate this by removing one animal, the leatherback sea turtle, from their ecosystem/ food web. • Ask students: o What do leatherback sea turtles prey on in this food web?

Answer: moon jellies

o What do moon jellies eat?

Answer: zooplankton

o What will likely happen to the number of moon jellies once leatherbacks have been removed? Why?

Answer: With fewer sea turtles eating moon jellies, the moon jelly population will increase. More moon jellies will eat more zooplankton.

Elaborate • Continue to trace the consumers down the food web. Ask students what will likely happen to each species at each feeding level. For example, with more predators preying on them, zoo- plankton numbers will fall. Since zooplankton includes fish larvae, fewer baby fish will grow to adulthood, meaning there will be less food for the rest of the web (this is because zooplankton is part of the base of the food web, after phytoplankton). • Going deeper: A decline in zooplankton could also possibly lead to an explosive growth of phytoplankton—algal blooms, which block sunlight from penetrating the water. And because some algal species produce harmful toxins, a variety of marine life may be seriously affected (meaning poisoned) as a result. Emphasize, however, that the myriad of relationships that exist within a food web in nature make it difficult to predict exactly how a food web will respond to being disturbed. 7 Evaluate • Now, have students apply this line of thinking to their own food web. Take the card for a consumer (other than leatherback sea turtles) from each team’s food webs—therefore “removing” it from the ecosystem. Tell students to trace the effects of the removal of this species through the feeding levels. Have students write their predictions on Student Worksheet 2. • Then, have students choose one of the scenarios in Student Worksheet 2 and use their food web to describe the impacts that might have on the ecosystem. Extensions (Optional) • As an extension, suggest students research whether the species they chose to remove from their food webs is endangered, and what kinds of pressures from human activities the species might be facing today. Use the following online resources for this research: o Fishwatch o NOAA Fisheries Have students include in their summaries an explanation of how an increasing human population can impact particular fish or other marine species and have far-reaching effects on open ocean ecosystems. Next Generation Standards Correlations Disciplinary Core Ideas • LS2.A: Interdependent Relationships in Ecosystems • LS2.B: Cycles of Matter and Energy Transfer in Ecosystems • ESS3.C: Human Impacts on Earth Systems Science and Engineering Practices • Developing and Using Models Crosscutting Concepts • Energy and Matter: Flows, Cycles, and Conservation NOAA Ocean Literacy Standards • Principle #5: The ocean supports a great diversity of life and ecosystems. • Principle #6: The ocean and humans are inextricably interconnected. • Developing and Using Models Crosscutting Concepts • Energy and Matter: Flows, Cycles, and Conservation

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