Purple sea urchins are usually kept in check by their main predator on California's North Coast: the sunflower sea star. It was also low in nutrients, stressing the kelp, and it lasted for several years.Īt the same time, a widespread disease was shifting the dynamics in the ecosystem. But in 2014, the ocean off California began warming.Ī mass of warm water in the Pacific Ocean, known as "the Blob," began expanding, raising temperatures high above normal. The towering seaweed reaches 30 to 60 feet tall.Īt its peak, kelp grows up to two feet per day in the West Coast's cold, rough waters, which are rich in nutrients.
They're a very bizarre animal."Īcross much of Northern California, purple urchins have little kelp left to eat, but still can survive.Ĭalifornia's kelp forests are not unlike redwood forests on land. "They can last for a long time without eating, and they can just live. "They're kind of like zombies," says Morgan Murphy-Cannella, kelp restoration coordinator with Reef Check California, a group of citizen scientist divers. Even now, with little food left, the urchins are still able to survive. Urchins are a normal part of the kelp forest, but a double whammy of ecological change has caused a population boom. The kelp's abrupt decline is being driven by warming waters, and it's a case of how climate change is helping push already-stressed ecosystems over the edge. Kelp forests provide a crucial ecosystem for a broad range of other marine life and animals, so their demise threatens the ecology across the entire stretch of California coast. Since 2014, 95 percent of the kelp have vanished across a large part of Northern California, most of it bull kelp. Purple sea urchins have exploded in recent years off California, covering the ocean floor in what divers describe as a "purple carpet." And they devour kelp: the once-lush forests of seaweed that hugged the coastline are disappearing. They're purple, spiky and voracious, and just off the West Coast, there are more of them than you can count. Purple sea urchins have boomed off Northern California, destroying kelp forests that provide a crucial ecosystem.
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