Heat-tolerant algae could save coral reefs from warming seas

of 31C, which is 3-4C above what they normally experience and comparable to the water temperature during the Great Barrier Reef bleachings.

When the algae were reintroduced into coral larvae they were found to have adapted to become more tolerant of heat and were able to share this benefit with the coral.

‘‘We found that the heat tolerant microalgae are better at photosynthesis and improve the heat response of the coral animal,’’ Madeleine van Oppen, one of the authors, from the University of Melbourne, said. ‘‘These exciting findings show that the microalgae and the coral are in direct communication with each other.’’

The scientists believe that the process could be scaled up to produce large amounts of heattolerant algae, which could be introduced to reefs.

Patrick Buerger, another author of the study published in Science Advances, said: ‘‘We can grow these heat-evolved algae strains in very high quantities in aquaculture facilities. The benefit of this potential intervention is that even a few types of these heat-evolved algae can form a symbiosis with many different coral species.’’

However, he said that more research was needed to check for potential side-effects on adult coral and demonstrate that the symbiotic relationship between the adapted algae and the coral was maintained over time.

The Intergovernmental Panel on Climate Change warned last year that almost all coral reefs would decline even if the world met the objective of the Paris

Agreement to keep the increase in global average temperature below 2C.

Scientists are exploring methods to save coral reefs, including replanting them with corals grown in nurseries, using robots to spread coral larvae and genetically engineering coral to produce species that are more heat tolerant. More extreme options include using underwater fans to create upwellings of colder water and even shading reefs with manmade structures.

– The Times