This summer there has been no shortage of coral bleaching stories in the news. However, this video of coral bleaching in Bali Indonesia hits home as we visited the same reef at Menjangan Island December 2015.
This video posted by Coral Reef Ecology and SCUBA Diving, chronicles changes witnessed in one year on the coral reefs of Bali Barat National Park, NW Bali (2015- 2016), most notably the sacred island of Menjangan. Several factors contributed to the widespread bleaching including a freak July storm followed by a crown-of-thorns starfish outbreak.
The combination of high temperatures and continued degradation of the reef through blast fishing, anchor damage, and diver damage have led to the decline of coral reef around Menjangan Island. This year’s extremely high seawater temperatures created a tipping point in Bali, resulting in severe coral bleaching including both hard and soft corals.
Coral bleaching occurs when the host coral expels tiny photosynthetic algae symbionts, which results in the coral losing their color pigment. If the environmental conditions return to normal quickly enough, some corals may regain their algae and associated colour.
Scientists have long known that higher ocean temperatures cause corals to expel their symbiotic algae. However, for the first time, researchers in Australia have captured a time-lapse video of coral’s bleaching behaviour. The video shows a long tentacle plate coral, Heliofungia actiniformis, expelling algae from their oral opening, through pulsed inflation.
One of the most startling results was how quickly the coral began expelling algae. Within two hours of setting up the experiment, researchers began noticing the coral belching green clouds of symbiotic zooxanthellae. Once the algae are expelled corals are susceptible to disease and can quickly die.