That’s not coral bleaching

Although some areas of Sulawesi have experienced coral bleaching, Gorontalo has not. Those diving here sometimes see white on coral and think something is wrong. Coral bleaching is generally associated with water temperatures that are too hot for the symbiotic bacteria that provides both color and food supplements to hard corals. As a result of the hot water

, bacteria dies, leaving the corals white in color and lacking sufficient food. If temperatures do not drop quickly enough for bacteria to return and provide needed nutrition, the corals will die. This phenomena hits many or all corals in a particular area, leaving the reef looking ghostly white.
Divers in Gorontalo marvel at the highly dense and diverse coral reefs here. But they also notice corals with white edges, particularly Acropora table corals. This is not bleaching, but an indication of healthy and rapid growth. Acropora corals always expand and grow along the edges. So in Gorontalo many edges are white since bacteria have not had time to develop inside this new growth.
Notice the white new growth in this photo of the edge of healthily Acropora table coral. The white coral polyps, looking like hairs, are out feeding in the current.