Most species of coral have an intimate, symbiotic relationship with algae that live inside their cells (called zooxanthellae). This algae provides the coral with energy from photosynthesis in return for the coral providing a place to live.
However, when surrounding water gets too hot, corals become stressed and expel their symbiotic algae. This is called “bleaching” because the algae are what give coral most of their color, so corals that have expelled their algae become white. Corals can re-recruit symbiotic algae if conditions return to normal, but if the coral remains stressed for too long it will starve and die.
Luckily, scientists have now successfully roduced created lab-grown algae that can resist bleaching in warmer water conditions. Although this is still in the preliminary stages, it indicates that it may be possible to one day seed wild reefs with bleach-resistant symbiotic algae that would make coral more heat-tolerant.
