sentences:  This has a considerable impact on the microhabitat and may be beneficial for the urchin as it results in an increase in the growth of the algae and bacteria forming the film round the particles of sediment.The red heart urchin has few predators but is sometimes preyed on by stingrays and other fish, loggerhead turtles and the sea star "Oreaster reticulatus".It can emit a noxious yellow exudate which repels fish and may even kill them.