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Balancing Act: Otters, Urchins and Kelp

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Learn about the connections among sea otters, sea urchins, kelp forests, and climate change. This video shows how conservation of wildlife can have an impact on global climate change. It provides examples of how healthy, balanced ecosystems will be the best offense in a rapidly changing ocean environment. This video is part of our Ocean Acidification Education series.

Kelp forests are extremely productive ecosystems that support a huge amount of marine life, and they are also efficient absorbers of CO2. Like any land-based forest, kelp forests sequester (take out) CO2 from the atmosphere through photosynthesis, transforming it into the energy they need to build their leafy structure. Kelp forests are at risk from sea urchins, small spiky marine animals that love to eat kelp. With no predators around, sea urchin populations can multiply, forming herds that sweep across the ocean floor devouring entire stands of kelp and leaving “urchin barrens” in their place.

Fortunately, sea otters have an appetite for sea urchins and they help to keep sea urchins in check, allowing the kelp to flourish and capture CO2. When otters are present, urchins hide in crevices and snack on kelp scraps. The kelp can flourish, providing habitat for many ocean organisms. Sea otters play a small role in mitigating global climate change, but their impact points to a larger lesson: wildlife conservation can save vegetation needed to reduce CO2.

 Pre-viewing Questions

  • What is an ecosystem?
  • What is a kelp forest?
  • What types of organisms live in a kelp forest?

Focus Questions

  • Why do kelp forests need otters?
  • What happens if there are no predators around to eat sea urchins?
  • What was the result when otters discovered sea urchins in the Strait of Juan de Fuca?

Post-viewing Questions

  • Why is it important to conserve kelp forests?
  • How do sea otters help to combat climate change?

Extension Activity

Draw or construct a healthy kelp forest ecosystem containing appropriate populations of kelp, sea urchins, and sea otters. Make a small-scale model or turn your whole classroom into a kelp forest.

Links to Learn More

  • UCSC Study Shows… Global Warming, University of California, Santa Cruz. This article outlines a study that suggests that thriving sea otter populations keep sea urchins in check, which in turn allow kelp forests to prosper.
  • A Snail’s Odyssey, Tom Carefoot. A summary of research studies about urchin populations and their relationship to kelp and otters
  • Sea Otter 101, Ocean Today, NOAA. A three-minute animated cartoon about sea otters
  • Ecosystems: Kelp Forests, National Marine Sanctuaries, NOAA. An explanation of kelp forests on the Pacific Coast, from Alaska and Canada to the waters of Baja California

Next Generation Science Standards

Performance Expectation:
Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment. 5LS2-1
Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems. MS-LS2-2
Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem. MS-LS2-3


Disciplinary Core Idea:
A healthy ecosystem is one in which multiple species of different types are each able to meet their needs in a relatively stable web of life. LS2A Interdependent Relationships in Ecosystems

Mutually beneficial interactions may become so interdependent that each organism requires the other for survival. LS2A Interdependent Relationships in Ecosystems

Food webs are models that demonstrate how matter and energy are transferred among producers, consumers, and decomposers as the three groups interact within an ecosystem. LS2B Cycles of Matter and Energy Transfer in Ecosystems

Crosscutting Concept: Systems and system models, patterns, stability and change

Science and Engineering Practices: Developing and using models, constructing explanations and designing solutions

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