Humans, sea otters, and many more sea creatures eat sea urchins
They eat algae, mussels, small fish, brittle stars, sponges, and crinoids.
The purple sea urchin eats kelp and is getting to be something of a scourge.
They have a mouth on the bottom of them. As they move along they eat algae & other detritus off the surface of rocks, coral etc. They have surprisingly strong mouth parts that chew out trails as...
Humans gut them out, and eat their insides. Talk about gross!!
because its their food, they usually eat shellfish and fish