in late 2005, water temperature was elevated for several months and it was found that S. trenchii, a symbiont not normally abundant, took up residence in many corals in which it had not previously been observed. Those corals did not bleach. Two years later, it had largely been replaced as a symbiont by the species normally found in the Caribbean.

Symbiodinium thermophilum was recently found to make up the bulk of the algal population inside the corals of the Persian Gulf. It is also present in the