When corals experience stress, they are discolored forcefully expel the algae living in their tissues and turn white. Australian researchers first captured this phenomenon on video.
Corals and algae that live in them are in mutually beneficial relationships. The corals provide the algae with protection and a surface for reproduction and photosynthesis. Sugar produced by algae, satisfy the nutritional needs of corals.
When the algae leave the coral, the pigment goes with them, and the corals become white or transparent. Some of the corals are coming back to normal state and re-settle in the algae. Other never colonized by symbionts and die.
To make this remarkable video, a scientist Queensland University of technology (Australia) had to come up using a microscope, digital camera and tablet. The researchers put a single coral Heliofungia actiniformis in 10-liter aquariums and heated water. The corals started to use a process called pulsed inflation to get rid of algae in 2 hours. The researchers raised the temperature in the tanks from 26 to 32.2 degrees Celsius for 12 days and kept it 8 days.
H. actiniformis swelled to 340 % of its normal size and then suddenly and dramatically declined and threw symbionts through the oral opening (greenish jet in the video).
Mass coral bleaching is causing concern among scientists worldwide. Recent events on the Big Barrier reef highlight the threat of increased water temperature for the health of reef ecosystems.