Coral bleaching happens when stressed corals lose or expel much of the symbiotic algae living in their tissues. Because those algae provide color and a major share of the coral's energy, the underlying white skeleton becomes visible through the transparent tissue.
What the science says
High ocean temperature is the leading cause of mass bleaching, although extreme light, pollution, freshwater exposure and other stresses can contribute. Heat disrupts the photosynthetic partnership and can generate cellular stress that makes continued symbiosis harmful.
How the process works
A bleached coral is not automatically dead. If stressful conditions ease soon enough, algae can repopulate the tissue and the coral may recover. Prolonged or severe bleaching, however, reduces energy reserves, increases disease risk and can lead to mortality.
What scientists measure
Bleaching severity varies among species, locations and individual colonies. Local conditions such as water flow, shading and prior temperature history can influence sensitivity, while repeated marine heat waves can leave less time for recovery.
Limits and open questions
Scientists monitor sea-surface temperature, heat stress and reef condition to identify risk and document impacts. Because bleaching is a physiological stress response, the long-term outcome depends on what happens after the coral turns white.
Why this topic matters
Understanding What Is Coral Bleaching helps connect individual observations to the larger scientific framework. Reliable explanations separate measured evidence from speculation, make uncertainty visible, and give readers a basis for interpreting new research as it appears.
