Sometimes nature surprises you. That’s what happened when a massive marine heatwave took hold in the waters around Moorea, French Polynesia, in late 2018. Fortunately, UC Santa Barbara researchers turned this event into an opportunity to investigate coral bleaching.

Scientists surveyed coral around the island during and after the heatwave, recording which colonies survived and which succumbed to the heat. They found that high ocean temperatures hit the largest coral hardest, an alarming result since the biggest colonies are most fertile. What’s more, the heatwave also decimated baby corals. These trends, detailed in Global Change Biology(link is external), suggest that heatwaves could entirely restructure the size distribution of corals on reefs.

“We had this big marine heatwave event, and we found that it kills the corals that make the babies — the biggest corals — and it kills the corals that are the babies — the ones that have just settled on the reef,” said senior author Deron Burkepile(link is external), a professor in UC Santa Barbara’s Department of Ecology, Evolution and Marine Biology. These groups of corals are disproportionately responsible for reef recovery.