Researchers from Queensland University of Technology captured how a coral reacts to heat stress. As seen in their video uploaded on YouTube, the coral called Heliofungia actiniformis expelled Symbiodinium, tiny algae cells that give corals their colors, quickly and violently, as a reaction to high water temperature.
The research team placed the coral into a 10-liter aquarium and increased the water temperature from 26 degrees Celsius to 32 degrees Celsius to replicate increasing sea surface temperature. To document how the Heliofungia actiniformis reacts to this environment, they used microscope, digital camera and smart tablet to capture time-lapse videos of the coral’s physical reaction.
Within the first two hours of their eight-day experiment, the coral inflated itself up to 340 times its size before ejecting its symbionts. According to Brett Lewis, a researcher from QUT’s marine facility in the School of Earth, this demonstrates that this coral species is actually vulnerable to coral bleaching. For many years, researchers incorrectly assumed that Heliofungia actiniformis is resilient to this phenomenon since it is one of the few coral species that did not experience bleaching like its neighboring species did.
“Our observations suggest this resilience could be due to the rapid expulsion of the coral’s algal symbionts during thermal stress, and could very well increase H. actiniformis’s chance of survival during abnormally high sea temperatures,” adds Lewis.
When the Symbiodinium, which produces sugar that feeds the corals, gets expelled, it usually returns to normal quickly enough when the environmental conditions improve. However, if the algae do not return quickly, the corals can die.
The research team adds that their discovery highlights mass coral bleaching around the world, including that of the Great Barrier Reef. Unfortunately, the Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies reports that 35 percent of the Great Barrier Reef is dead.