Until recently, giant seaweed called bull kelp formed lush underwater forests in northern California's coastal waters. These kelp forests have long provided critical habitat for many species like salmon, crabs, and jellyfish. But now a few patches of bull kelp remain. Warming waters and hungry urchins make it hard for these kelp forests to survive.

The study shows the destruction of the kelp forest was related to an explosion in the population of purple sea urchin, which eats it, and two warm water events that lasted from 2014 to 2016.

Similar to what has happened in B.C., tens of millions of voracious purple sea urchins have chomped their way through towering underwater kelp forests in California.

Giant kelp (Macrocystis pyrifera) is normally found in Prince William Sound and Kodiak Archipelago. However, it has recently appeared at the north end of Zachary Bay near Sand Point.