Survival of the Fattest: Corals Adapt to Climate Change by Getting Fat

Forget "survival of the fittest;" it's survival of the fattest, in this case. Scientists have found that the future health of the world's coral reefs and the animals that depend on them relies on corals' ability to keep large fat reserves.

Corals are tiny, reef-forming animals that live symbiotically with algae. Yet corals have been under severe stress in the face of climate change and warming temperatures. In fact, they have been experiencing yearly bouts of heat stress which results in "bleaching." While some corals recover, others die off. Now, researchers have found out how these corals can survive these events.

During a bleaching even, corals essentially eject the algae living inside their cells. Algae are what give corals their brilliant brown, yellow and green hues, so the corals appear white after bleaching. These bleached corals can eventually recover by growing more algae or acquiring new algae once water temperatures return to normal. Yet corals' ability to switch the type of algae that they internally grow has a large effect on their recovery.

In order to better assess how corals adapt to bleaching, the researchers tested three corals from Puerto Morelos Reef National Park. In the end, they found that corals with lower fat reserves partnered with only one algal species and had a harder time recovering from bleaching. The coral with moderate fat reserves that could partner with six different algae could still recover, though its growth slowed. The coral with the highest fat reserves and which completely switched from one algal partner time to another, in contrast, maintained a healthy growth rate and recovered from bleaching.

The findings reveal that some species can adapt to climate change. That said, other species will be climate losers, which will mean that there will be less diversity on reefs. Even so, it shows that reefs likely won't fail completely.

"We're actually a bit optimistic, because we showed that there's acclimation in a one-year window, that it's possible," said Andrea Grottoli, one of the researchers, in a news release. "In two of our three coral species, we have recovery in six weeks. The paths they took to recovery are different, but they both got there."

The findings are published in the journal Global Change Biology.