The answer is D. Global warming causes the ocean temperatures to rise and also its pH to decrease due to increased dissolved carbon dioxide in the waters. Due to the unfavorable temperatures and pH, the algae dissociate from the symbiotic relationship with coral polyps (as a survival mechanism) hence leaving the coral white (coral bleaching). The symbiotic relationship is key for the survival of the coral polyps hence most die following the dissociation. This upsets the reef ecosystem and affects all aquatic organisms that depend on the reef.
