Jellies play a big role in Earth's oceans
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Jellies live in every ocean, from the equator to the poles and from the surface to the depths. Whatever we do to the oceans also affects the world of the jellies.
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Our actions create classic problems
The Bering Sea is an extremely productive region, accounting for up to five percent of the world's total fishery production. During the 1990s, the number of sea nettles in the Bering Sea increased by 10 times—clogging fishing nets and the intake pipes of power plants. Scientists think overfishing and climate change caused the increase. With fewer fish to compete with for food, jellies bloom out of control.
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Jelly blooms can mean a system out of balance
Around 1980, warty comb jellies invaded the Black Sea, accidentally transported in the ballast water of ships. Today, the jellies devour most of the plankton in the Black Sea, leaving little food for native anchovies—a fish local people depend on. With no natural predators to keep them in check, comb jelly blooms sometimes number more than 300 comb jellies per square foot.
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Moon jellies have also hitched a ride in the ballast tanks of seafaring ships. Today, huge blooms of moon jellies compete with native animals by eating up their prey.
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Coastal runoff and habitat destruction
The upside-down jelly and box jellies live among the underwater roots of mangrove trees, in one of Earth's most threatened habitats—coastal mangrove forests. When people cut down mangroves to make room for buildings and fish farms, jellies—and countless other animals—lose their homes.
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