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To see what defense the coral has already had against warm water, Meibom and his colleagues wanted to learn how much heat the coral and their complex network, called the holobiont, can withstand. It equates to testing the strength of a rubber: how long can you stretch it before it breaks? And how long does it take to return to normal shape?
Karine Kleinhaus, who studies corals at Stony Brook University, says it is essential to understand how these corals work at the cellular level. “These amazing corals will be the last to survive” XXI. Until the end of the century, he says. “We have to figure out what they’re doing, what’s going on, how they’re doing it.”
In their experiment, the researchers grew S. pistillata in several aquariums it was named the Red Sea Simulator. Each aquarium could be customized to replicate specific water conditions and show corals, algae, and bacteria at different temperatures for different periods of time. The researchers then looked at what state the coral indicated in the gene normally, how it changed as the temperature rose, and when the temperature decreased, that gene activity returned to normal.
All three organisms found that they were able to change which genes they used as the water heated up. Corals, for example, promoted the use of genes involved in the development of undeveloped proteins to detect environmental stress. save homeostasis gelaxkan; in other studies, it has been described as coral first line of defense against the heat. Meanwhile, algae denied the activation of genes associated with photosynthesis. In general, Red Sea species were able to survive until the temperature warmed to more than 5 degrees. And after scientists lowered the temperature in the tanks, the entire holobiont returned to normal, even in hot conditions for a week. . Meibom equates his endurance with an excellent athlete who is able to recover quickly and be ready for another challenge after training.
“The paper does a good job and sheds light on the early stages of the heat stress response in thermally tolerant corals,” says Andréa Grottoli, a professor at the Ohio State University School of Earth Sciences who studies coral and climate change. he noted that this approach has some limitations. Activating genes does not mean that corals will eventually produce new proteins. It indicates that the coral responds to the environment, but it’s not the whole story. also want to know exactly what biochemical changes it was making to adapt, and how these physically alter the coral.
Grottoli also noted that the longest exposures in the study, up to seven days, are shorter than many real-life heat waves. “Most natural bleaching events last two months,” he says.
Meibom agrees that his research does not explain how these newly activated genes can help the coral survive, but he says that identifying them is the step to take. “It gives advice on what to do.”
It is also not clear why these corals have this resistance to heat but others do not. Maybe it’s not because they’ve evolved in the hot climate of the Red Sea, but because they’ve come even hotter from some places. Meibom theorizes that about 20,000 years ago in the ice age it may have been related to what species they populated during the last ice age. The water around the equator evaporated and eventually froze in heavy frosts. With all this water trapped in the ice, sea levels dropped, cutting the Red Sea off the Arabian Sea, essentially turning it into a lake. The water level dropped and salt accumulated, making it the perfect atmosphere. But when the glaciers melted and the connection to the rest of the ocean was repaired, new forms of water and life overflowed. This included corals living in the Arabian Sea, which slowly rose from the warmer waters of the south. Only these heat-adapted species were healthy enough to send their larvae north to repopulate the Gulf of Aqaba. “They were chosen. It’s like a filter, ”Meibom says.
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