Molecular techniques explain how the corals of the Great Barrier Reef survived harsh conditions

In a groundbreaking new study, scientists used innovative molecular techniques to explain how corals on Australia’s east coast survived previous harsh conditions, allowing the Great Barrier Reef to become the vast coral reef it is today.

We sequenced the genomes of 150 individual colonies of the same coral species and used it to find out which genes are important for survival in coastal reefs.. “

Dr Ira Cooke, lead author of the study, James Cook University

“Genomes are like a time capsule containing an enormous wealth of historical information,” said co-author, Professor David Miller of the ARC Center of Excellence for Coral Reef Studies (Coral CoE).

‘In general, single genomes are really useful in coral studies, but hundreds of genomes for the same species are a goldmine of information,’ said Professor Miller.

The team delved into the ancient history of coral reefs, back around a million years, until the coastal corals of Magnetic Island first separated from their northern reef relatives.

Scientists mapped the rise and fall of these two coral populations on the Great Barrier Reef, tracking which genes evolved rapidly to withstand changing conditions, measuring the flow of genes between locations.

They say the findings are important for the current and future conservation of coral reefs.

Dr Cooke and his team already knew that corals on the coastal Great Barrier Reef were able to thrive despite a disruptive environment of high turbidity and highly variable salinity and temperature parameters. By looking at the variation between genomes, the team discovered exactly how corals achieved this feat.

Survival strategies used by coastal reef corals include a number of genes that have evolved rapidly over the past 10,000 years. This time period includes the floods after the last ice age. Another strategy includes the assimilation of special strains of symbiotic coralline algae. These have been found in coral reefs with some of the harshest conditions, often near rivers.

“These two strategies deserve special attention in future studies as possible keys to coral survival under similar conditions,” said Dr Cooke.

“The loss of these coral reefs is a future possibility as coral reefs currently undergo unprecedented, drastic and rapid changes due to human influence,” said Professor Miller.

“Coral reefs are threatened by climate change, overfishing and pollution.”

In addressing the latter, Dr. Cooke says it is very important to take care of reservoirs and water quality.

“As high-quality genomic assemblies derive from a wider range of corals and their symbionts, this and related approaches will become key tools,” said the authors.

“These bring us closer to understanding the interaction between past climatic conditions and the evolution of corals and coral reefs.”