The coral, in return, provides the algae with a home, nitrogen, and phosphorous. The algae depends on nitrogen and phosphorous for its survival. It is for these reasons that corals thrive in warm, clear water. The causes of death for coral are varied. Predation by parrotfishes, butterflyfishes, and sea stars is one of nature s ways of controlling the coral population.
Corals can also die due to natural disasters.
For example, a change in sea level would cause the death of corals. If sea level drops, the corals are exposed. If sea level rises, it will decrease the amount of sunlight that is able to reach the corals. Human interaction, unfortunately, also causes the death of corals. Human interaction in the form of ocean pollution causes corals to die.