It turns out that some corals may survive bleaching events by being promiscuous. Scientists have found that corals can acquire and host new types of algae from their environment in order to outlast warmer temperatures.
Coral bleaching takes place when the microalgae living within coral polyps die off. This leaves the coral tissues "bleached" white. The microalgae themselves not only provide corals with their vibrant colors, but also give the corals the ability to photosynthesize. In other words, they help provide the corals with food.
In this latest study, the researchers used new DNA sequencing techniques to analyze thousands of algal symbionts from corals at a subtropical reef at Lord Howe Island during and after coral bleaching events that occurred in 2010 and 2011. More specifically, the researchers monitored the diversity and dominance patterns of the microalgae present in the coral tissues, and they found that there was an extraordinary range there. More interesting, though, was the fact that after bleaching events, the corals that survive actually picked up microalgae that were more resistant.
"This new study will cause a paradigm shift in our understanding of corals that build reefs," said Nadine Boulotte from Southern Cross University, one of the researchers involved in the new study. "Our study shows for the first time that some adult corals can be promiscuous, and swap their algal partners later in life. This algae partner-swapping could help corals to better adapt to climate change and survive bleaching events if they can acquire more heat-tolerant microalgae."
The findings are huge when it comes to better understanding how corals react to and recover from bleaching. More specifically, it shows that corals may do far better than first expected as they respond to climate change.
"Given the severe coral bleaching event on the northern Great Barrier Reef and some other regions around the world that is killing many corals, and the increasing threat of catastrophic bleaching events into the future as sea temperatures continue to warm, the research is timely," said Peter Harrison, director of SCU's Marine Ecology Research Center. "We need to expand this research from the subtropical region into tropical reef areas, where most coral reefs occur and where mass bleaching events are severely impacting coral communities, to see if other types of corals can select new algal symbionts."
The findings are published in the April 19 issue of the journal ISME Journal.