Closer Look: Dramatic 'Coral Bleaching' Captured on Video for the First Time
Early this year, massive coral bleaching has wiped off 93 percent of the iconic Great Barrier Reef, Australia's heritage site and the world's largest living ecosystem.
Coral bleaching, in which corals expel their algae and turn white, is a result of environmental stress. In an attempt to demonstrate how coral bleaching is happening up close, Australian researchers have captured this phenomenon on video for the first time.
For the study, researchers from Queensland University of Technology placed solitary corals, Heliofungia actiniformis, in a controlled 10-liter aquaria. They then raised the water temperature (from 26 degree Celsius to 32 degree Celsius over 12 hours, where it remained for up to eight days) to see how the corals would react.
The scientific behavior of the algae removal was captured using a microscope, digital camera, and tablet.
"What's really interesting is just how quickly and violently the coral forcefully evicted its resident symbionts," said Mr Lewis, from QUT's Science and Engineering Faculty in a press release.
"The H. actiniformis began ejecting the symbionts within the first two hours of us raising the water temperature of the system."
International Union for Conservation of Nature describes H. actiniformis as widespread and locally common throughout its range. This species is particularly susceptible to bleaching, disease and other threats. The study revealed H. actiniformis are used because of such resiliency.
According to National Oceanic and Atmospheric Administration (NOAA), the symbiotic relationship between the corals and algae breaks down as ocean temperatures rise.
It added that corals that are bleached do not necessarily mean they are dead. If the ocean temperature returns to normal quickly, the algae may return and the corals might return from its former shape. Otherwise, the prolonged stress may result to their eventual mortality.
"Our H. actiniformis used a pulsed inflation to expel Symbiodinium over time (seen as greenish plumes in the video) -- inflating their bodies to as much as 340 per cent of their normal size before suddenly and violently contracting and ejecting Symbiodinium through their oral openings over the four to to eight day duration of the experiments" Dr. Nothdurft said.
The timelapse was described in the journal Coral Reefs.
Understanding coral responses to thermal stress is important for predicting how corals will fare with elevated ocean temperatures.