Bleached brain coral
This large bleached brain coral has expelled its symbiotic algae. This algae provides the color to coral tissues, and it also provides the coral polyps with food by way of photosynthesis. Coral bleaching was the worst on record in 2016, when prolonged elevated water temperatures stressed corals to the point that they expelled their symbiotic algae. Once the algae has left the coral tissue, the stark white calcium carbonate skeleton is visible through the transparent coral tissue, giving it a "bleached" appearance. If the water temperatures stay too high for too long, and the corals do not re-recruit their algae, corals may starve and die. Fortunately this was not the case: the water temperature has decreased, and the corals have been able to re-recruit their symbiotic algae and recover. Another interesting feature visible in this area is the large amount of algae in the sand flat, which could also be a result of 2016's warm water conditions.