Sea Otter Heroes: The Predators That Saved an Ecosystem

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Marine biologist Brent Hughes didn't think sea otters and sea grass had much in common. But his research at Elkhorn Slough, an estuary on Monterey Bay in northern California, revealed a new and surprising connection between the two. The scientist expected this estuary to be overrun with algae due to the fertilizer runoff from surrounding fields. But it wasn't. Brett's answer: sea otters. The otters eat crabs, which prey on sea hares, a type of mollusk. Fewer crabs mean more sea hares. The sea hares consume algae, thereby allowing sea grass to thrive. This set of relationships within a food chain is known as a trophic cascade.