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One Critical Critter Sea urchins can travel in large herds if there are no predators to keep them in check. Groups like these can destroy 9 meters of kelp forest in a month. If this damage isn’t stopped, there will be no forest to convert carbon dioxide into oxygen. T ere will be no forest to provide a hiding place for young fi sh and other animals. Fortunately, a solution swims by. It’s not

another seal. It’s an otter. With whiskered faces and thick, sleek fur, sea otters keep kelp forests healthy by eating sea urchins. T ey don’t consume all of the urchins, but

enough so that the urchins can’t form large herds. T ese otters are a keystone species for the kelp forest ecosystem. Just as a keystone rock in an arch supports all the other stones, sea otters support all the other species in a kelp forest. Without the keystone, everything can fall apart. You watch the sea otter grab a rock and head

for the holdfast. It uses the rock as a crowbar to pry up two of the urchins. Aſt er placing the rock beneath its leſt armpit, it seizes an urchin in each furry paw, and heads for the surface.

An otter wraps itself in kelp to anchor itself in the water.

Return to the Surface Your oxygen tanks are almost empty. So you signal to your dive partner, and you both begin your ascent. Once topside, you hail your boat. Both of you heave yourselves aboard. While removing your gear, you spot the sea

otter. He has broken apart the urchins and is eating them. T e two other scientists climb aboard. By the time they have their gear off , the otter has wrapped himself in some kelp to stop him from fl oating away. He’s sound asleep! Your mission is complete. It’s good that

you took such careful notes. You know your research today will help the kelp in Monterey Bay. And you look forward to your next dive into the underwater forest.

WORDWISE consumer: a living thing that eats other

living things for food

decomposer: a living thing that breaks down wastes and remains of other organisms

ecosystem: all living and nonliving things in an environment and how they interact

keystone species: a species on which other species in an ecosystem depend

photosynthesis: the process of living things using sunlight to make food

producer: a living thing that makes its own food


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