Team of researchers sequenced and analysed the genomes of 15 different species of coral to better understand how its genetic make-up enables it to survive warmer oceans as a result of climate change.
Researchers from the Marine Genomics Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), the University of Tokyo, and Seikai National Fisheries worked together to gain insight on whether Acropora corals are genetically equipped to handle a warmer ocean.
Alongside Professor Satoh and Dr. Shinzato, the research team also included Dr. Konstantin Khalturin, Dr. Jun Inoue, Dr. Yuna Zayazu, Dr. Miyuki Kanda, and Ms. Mayumi Kawamitsu from OIST, Mr. Yuki Yoshioka from the University of Tokyo, and Dr. Hiroshi Yamashita and Dr. Go Suzuki from the Seikai National Fisheries Research Institute.
“Acropora corals are especially susceptible to bleaching and are expected to decline in the future,” said Professor Noriyuki Satoh, from the Marine Genomics Unit at the Okinawa Institute of Science and Technology Graduate University (OIST).
“This is an issue because Acropora corals are very important. They grow quickly compared to other corals, which helps with reef growth, island formation, and coastal protection. And they also provide a habitat for more than a million species of marine organisms.”
Analysis of the genomes of 15 species of Acropora coral, together with three species outside of this genus, the scientists could shed light on its genetic ancestry and understand when these organisms evolved and when they split from close relatives to form new species. This study, published in Molecular Biology and Evolution, has revealed the evolutionary history of Acropora corals, with some surprising results.
“We found that the Acropora ancestor diverged from other corals around 120 million years ago,” Professor Satoh explained. “And the diversification of Acropora corals, when we start to see a lot of different species appear, occurred 25 to 60 million years ago. For both events, this is much earlier than previously thought.”
This key finding showed that Acropora diversified when the world’s oceans were much warmer than today. It was able to survive through other harsher climate change events such as the ice age, pointing that its genetic make-up allows it to withstand drastic changes in temperature.
Lead author Dr. Chuya Shinzato, a former staff scientist at OIST and now an Associate Professor at the University of Tokyo, analyzed the genomes and found that these 15 species could be divided into four groups. Dr. Shinzato and the group then compared in detail which genes had been conserved and which genes were lost.
It was revealed that before this coral genus diversified, several mutations occurred which saw it gain 28 additional gene families. These genes likely contributed to this diversification and its success in spreading across the globe, together with its ability to handle a range of temperatures.
"There were three notable additions from this time period, which could allow these corals to withstand high-stress environments," Professor Satoh said. "Two of these have been identified before and are associated with responding to environmental stress, usually heat."
This study also revealed for the first time through genome analysis, the presence of the gene that encodes DMSP lyase in Acropora corals. This gene allows the corals to produce a compound, dimethyl sulphide, in the water that, when transferred into the air, aids in the formation of clouds. This suggests that when temperatures get too high, the Acropora corals might be able to create small cloud umbrellas, which can protect them by providing shade and filtering out the light.
Professor Satoh, however emphasized that importance of understanding that despite the current research bringing insight to the evolutionary history of the Acropora coral, it is still far from concluding whether it is able to survive predicted rising ocean temperatures and coral bleaching events in the future.