A common resident found in kelp beds, rocky shores, and coral reefs is the sea urchin. It has a healthy appetite for organic material and feeds on kelp as pieces drift by. Sea urchins like this Purple Sea Urchin (Strongylocentrotus purpuratus) can be harmful to kelp forests and can destroy reefs when their populations multiply rapidly and overpopulate an area. They damage kelp forests by chewing through kelp holdfasts in search of food. (photo: Laura Francis)