Video of the violent spasms of a coral being bleached
We all know coral bleaching is dramatic – transforming wonderful, colourful reefs into sterile death zones. And now for the first time you can witness the awful moment when life actually flees from a coral in a unique film made by Australian researchers.
Scientists at Queensland University of Technology, Australia have recorded the gruesome response coral has as the water surrounding it is raised in temperature.
Scientists set up a controlled environment using Heliofungia actiniformis, a coral species, and symbiotic algae.
Over the first 12 hours they increased the water temperature in the controlled environment from 26°C to 32°C and left it at 32°C for eight days. Within two hours of the temperature increase the coral started to excrete the algae it was housing.
'What’s really interesting is just how quickly and violently the coral forcefully evicted its resident symbionts,' said Brett Lewis from the university.
This coral species has a high tolerance to rising water temperatures, increasing their resistance to permanent damage occurring from coral bleaching.
Brett Lewis continued: 'Our observations suggest this resilience could be due to the rapid expulsion of the coral’s algal symbionts during thermal stress'.
They observed as the coral continued to pulsate over the eight days until all the algae were expelled, resulting in the coral turning skeletal white. Their study was published in the journal Coral Reefs.
Luke Nothdurft from the team described the reaction: 'H. actiniformis used a pulsed inflation to expel symbiodinium over time – 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'.
Coral feeds off sugars deposited by algae’s photosynthetic process. If the water conditions that caused stress on the coral do not return to normal and algae cannot re-inhabit the coral, it will starve and die. If the conditions do return to normal relatively soon the coral will stay alive becoming colourful again.
By continuing research, scientists are hoping they will understand what is causing coral bleaching in more depth and prevent it happening. Some scientists are also looking at having a response process to the initial phases of coral bleaching.
Currently, 93 per cent of the Great Barrier Reef has been affected by coral bleaching; the majority of this is in the northern section. This year's bleaching, the worst on record, has been blamed on the impact of a strong El Nino effect on ocean temperatures accentuated by global warming. Researchers fear this could get worse if water temperatures continue to rise again next year .