A staggering 93 percent of the Great Barrier Reef is already suffering from coral bleaching, as a comprehensive reef survey confirmed this week. But not all may be lost, as there are still ways for corals to survive these dire events.
For the first time, researchers showed that some corals that survived bleaching can obtain and host new kinds of algae from the environment, making them more tolerant to heat and better geared for recovery.
According to lead researcher and Southern Cross University postgraduate student Nadine Boulotte, most corals were previously thought to acquire microalgae while they’re still young – and to harbor the same kinds of algae their whole lives.
“Our study shows for the first time that some adult corals can be promiscuous, and swap their algal partners later in life,” said Boulotte, who worked with a team of scientists from the University of Melbourne as well as other Australian and U.S. organizations.
The swapping activity could assist corals in getting more heat-tolerant microalgae and eventually adapting to global warming and bleaching situations.
Bleaching takes place once the microalgae found in coral polyps start to die off and leave the tissues of the dead white. The microalgae provide corals the energy they need to build reefs, survive, and stay in mutually beneficial relationships.
Using novel DNA sequencing, the team analyzed algal specimens from corals at Lord Howe Island in Australia during and post-bleaching events in 2010 and then 2011.
Tracking the patterns followed by microalgae in polyp tissues in two species of corals, they detected “an extraordinary range” of various microalgae types in the corals. The survivors seemed to have obtained new algae types from their environment, with one microalgae proliferating well and occupying around a third of the community in the sampled corals.
Contrary to previously thought, taking up new microalgae types happened not just in coral larvae and in the juvenile phase – offerings corals at different life stages a chance at coping with rising sea temperatures.
Co-author and Director of SCU's Marine Ecology Research Center Peter Harrison deemed the research timely in light of the severe coral bleaching currently afflicting the northern Great Barrier Reef. He called for expanding studies from subtropical areas to tropical reef regions, where a majority of coral reefs exist and bleaching severely affects the coral populations.,
Lord Howe Island corals have not been seen to bleach this year, but previous events demonstrated that even the world’s southernmost reef is not fully shielded from massive bleaching.
The findings were published in The ISME Journal.
The Great Barrier Reef’s massive bleaching is feared to bring about grave ecological and economic consequences. Even its world heritage status is in danger of being revoked – UNESCO decided in 2015 to exclude the reef from its “in danger list,” seeking an update from the Australian government on progress made in water and reef quality improvements.
Photo: NOAA National Ocean Service | Flickr
