These reefs are among the most heat-tolerant on earth, and scientists are trying to work out why.
Coral bleaches when the water gets too warm: the algae living inside the coral leave, and without them the coral starves. Reefs across the Pacific and the Caribbean have lost enormous ground to it.
The northern Red Sea has largely not. The prevailing theory is a bottleneck: corals recolonised this sea after the last ice age by passing through the very warm southern strait, and only the heat-tolerant ones made it. Their descendants inherited a tolerance far above the temperatures they now experience.
That makes these reefs globally significant — possibly one of the last places coral will persist as oceans warm — and it makes local damage matter more, not less. What kills coral here is physical: fins, anchors, sunscreen chemicals and sediment from coastal building.
The prevailing theory is a bottleneck: corals recolonised this sea after the last ice age by passing through the very warm southern strait, and only the heat-tolerant ones made it.
Practically: never stand on coral, keep your fins up and away, use mineral sunscreen or a rash vest instead of chemical filters, and take nothing off the reef. A coral head the size of a football can be older than you are.
