A purple urchin at the Bodega Marine Lab. Tens of millions have already chomped through towering underwater kelp forests in California. (AP)
A destroyed kelp forest is filled with purple sea urchins off the Oregon coast. (AP)
Steven Rumrill, a shellfish expert, places his hand next to the shells of red sea urchins to show how big they can grow. (AP)
Karl Menard checks tubs of purple urchins harvested in California and now fed to make them big enough to sell for food. (AP)
The inside of the sea urchin (called roe, or uni) is the part people can pull out and cook for food. (AP)
Oh no! The ocean floor is changing colors. It has a carpet of round purple critters.
They creep on the sand. They eat up kelp. Seaweed is gone. The sea floor is empty.
Purple sea urchins have taken over.