Trophic cascade: otters, urchins, and kelp balance
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Kelp forests are underwater ecosystems anchored by giant kelp. Sea urchins graze on kelp holdfasts. Sea otters are a keystone predator — they eat urchins, keeping populations in check. Without otters, urchins overgraze kelp, creating "urchin barrens." Warmer waters stress kelp and promote disease. This demonstrates a classic trophic cascade.