Adjustments in response to natural stress

The shape of individual reefs and coral cays is a response to prevailing winds, waves, currents and the relict topography. Storm damage creates greater diversity in reefs, even though in the short term the reefs are damaged. If high water temperatures, fresh water, nutrient overload or sediment blanketing stresses a coral polyp, it usually expels the zooxanthellae and dies. This is called coral bleaching and the cause is not always natural. Furthermore, there is great debate on whether infestations by the poisonous crown-of-thorns starfish are naturally reoccurring phenomena or not. And whether the Great Barrier Reef has adjusted to these natural stresses.