Researchers have identified the genetic changes that cause corals to bleach when ocean temperatures increase. This insight gives researchers the possibility to genetically engineer corals to make them more resistant to bleaching. 

At normal temperatures, corals form a symbiotic relationship with microalgae, known as dinoflagellates. The algae provide their photosynthetic products to the coral so it can build its skeleton and the coral gives the algae CO2, inorganic nutrients and shelter from the waves. However, when sea temperatures increase the coral expels the algae in a process known as bleaching.

Coral bleaching events are becoming more common as climate change causes the ocean temperature to increase. Usually the bleaching is irreversible and permanently destroys the corals. Until recently, there was little understanding of the genetic changes that take place to cause bleaching, which could give scientists a possible mechanism for preventing it.

Scientists undertook transcriptomic analysis on the sea anemone Exaiptasia diaphana, both when it had symbiotic algae and when it did not. The analysis was investigated at a range of different temperatures.

It was revealed that temperature affected gene expression in both the sea anemone and its resident algae. Most gene expression changes impacted the symbiosome, which is the compartment inside the coral cell which hosts the algae.  Increasing temperatures affected the lysosome meditated degradation and transportation of carbohydrates through the symbiosome membrane. This could cause the symbiosis to become increasingly unstable at high temperatures.

This discovery could enable researchers to genetically engineer corals to be more resistant to bleaching. As both sea temperatures and acidity rise, researchers are expecting bleaching incidents to increase even more. This would have devastating effects on ocean ecosystems and on local communities.