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© Victoria Chapman & Associates CASE STUDY: HOW LOSING A KEYSTONE SPECIES CAN COLLAPSE AN ECOSYSTEM Sea otters live in Pacific Ocean kelp beds. They prey on sea urchins, crabs, abalone, fish, and other sea life. In the 18th and 19th centuries, fur trappers hunted sea otter populations to near extinction. Published by Facts On File, Inc. All electronic storage, reproduction, or transmittal is copyright protected by the publisher. Without sea otters to prey on them, sea urchins multiply and overgraze kelp and other seaweeds. They nip off the holdfasts that anchor kelp to rocks, creating a barren sea floor. The many species that rely on kelp forests for food and shelter disappear. Kelp Sea urchins Kelp holdfast Surviving populations of sea otters have been reintroduced to some of their former home sites. With the return of the sea otter, the kelp forests have grown back. The sea otter is a keystone species. When it is removed, the kelp forest community changes drastically.