Voracious Purple Sea Urchins are ravaging Kelp Forests on the West Coast, the trouble started in 2013, when sea stars, an urchin predator, began to die off.

The coastal waters of northern California were once home to undulating forests of bull kelp, a type of seaweed that offers shelter to a host of sea creatures. But a series of adverse ecological events have jolted the region’s marine ecosystem out of whack. Populations of purple sea urchins, a voracious, kelp-eating species, have exploded. And now, according to a new study in Scientific Reports, more than 90 percent of bull kelp canopy along 217 miles of California’s coast is gone.

As is usually the case when part of an ecosystem collapses, the decimation of bull kelp forests has had a devastating ripple effect. According to the study, 96 percent of red abalone, a type of sea snail that feeds on bull kelp, have died from starvation. Red sea urchins, which are bigger and meatier than their purple relatives, are similarly declining from a lack of food. Last year, a recreational abalone fishery worth $44 million had to close. The north coast commercial red sea urchin fishery has collapsed.

https://www.smithsonianmag.com/smart-news/voracious-purple-sea-urchins-are-ravaging-kelp-forests-west-coast-180973412