The Washington Post
Tiny algae may be helping coral reefs in tropical Pacific survive in warming seas, researchers say
Increased dominance of heattolerant symbionts creates resilient coral reefs in near-term ocean warming
Research published this month in the journal PNAS suggests that microscopic algae are helping reefs in the eastern tropical Pacific survive in a warming ocean.
This is good news given that coral reefs are home to a quarter of all marine species and that they protect coastal shorelines from erosion and provide essential fisheries around the world.
But these delicate reefs are also at particular threat from humancaused climate change. As the planet’s oceans have warmed, over half of its coral reefs have been damaged.
The PNAS study looked at data from the Uva Island coral reef in Panama. The reef has experienced — and bounced back from — multiple heat waves between 1980 and 2018.
The reefs of the eastern tropical Pacific along the coasts of Colombia, Costa Rica, Mexico and Panama are shallow, and most consist of Pocillopora, a type of stony coral that looks like cauliflower. They host tiny algae that pay them back in energy from photosynthesis, and when these algae die in warm waters, the corals bleach and eventually perish.
But reefs that hosted higher numbers of heat-tolerant Durusdinium glynnii algae withstood warmer waters better than those with lower numbers, the researchers found. In an example of a phenomenon called “symbiont shuffling,” the corals hosted higher numbers of heat-tolerant algae as the ocean warmed.
When researchers modeled future climate change scenarios, they found that the reefs hosting higher populations of D. glynnii were likelier to survive warming through the 2060s. In contrast, some studies suggest that the world’s reefs will survive until 2050 at best.
“This study shows that there are some unusual reefs that may be able to survive for several decades as a result of their ability to shuffle symbionts,” said Andrew Baker, a professor of marine biology and ecology at the University of Miami and the study’s senior author, in a news release. “While we don’t think that most reefs will be able to survive in this way, it does suggest that vestiges of our current reefs may persist for longer than we previously thought, although potentially with many fewer species.”
There’s still a chance to save coral reefs, the authors write: If humans managed to get their greenhouse gas emissions under control, the global warming outlook — and forecast for the world’s reefs — could improve.
If not, they suggest, the surprising resilience of the Eastern Pacific’s reefs will eventually give out, consigning its vibrant corals and the life they host to the same fate as other reefs.