StarFish , Sea Urchins , Anemones StarFish , Sea Urchins , Anemones StarFish , Sea Urchins , Anemones edit--That is incorrect. I know that only because sea urchins are actuallly primary consumers. I don't know about the rest of the answers.
The kelp uses the sea urchins to keep it in check, from growing too much. However, the sea urchins eat kelp, so they destroy kelp growth. Also, sea otters eat urchins, and they live in the kelp forest.
Sea urchins eat very slowly but like many other animals, they eat on a daily basis. A sea urchin's diet consists of things like algae and seaweed. If this food is not available, they will eat things like dead animals and sponges.