Simplify the following text for a Grade 7 native English-speaking person.
Original: The crown-of-thorns starfish has gained notoriety as a threat to the coral reef ecosystem , particularly in the Great Barrier Reef off the coast of Australia . Overpopulation of crown-of-thorns has been blamed for widespread reef destruction .
Simplified: However , when there are too many Crown-of-thorns , they can devastate a coral reef .