A study reported encouraging news after monitoring thousands of corals at reefs in Leeward Maui from 2014 to 2021, charting growth and survival rates through two major bleaching events.
Scripps Institution of Oceanography researcher Orion McCarthy and University of Hawaiʻi researcher Morgan Pomeroy followed individual corals over the years by creating 3D models from underwater photos.
"We saw that for corals that survived the entire time series and survived both bleaching events, that there wasn't a difference for most of the species between corals that bleached and corals that didn't bleach in terms of how they grew," McCarthy said. "So that was really surprising."
He said they initially expected to observe lingering effects from the bleaching, such as reduced growth and partial mortality.
The findings are important for informing coral restoration efforts, the researchers said, because the focus has been thermally tolerant corals that can survive bleaching events.
"If you spend all that time and effort doing restoration, you obviously want it to be effective, and you don't want to lose all those corals to a future heat wave. But like anything in ecology, there can be trade-offs," McCarthy said.
A more thermally tolerant coral may not bleach, but it also may not grow as fast during non-bleaching years, inadvertently creating a less diverse and adaptable reef, he said.
"This study is showing how climate change is transforming reefs, is weeding out certain individuals and leaving behind a reef that might be a little bit more stable because it's composed of survivors, but it's lost something. It has less diversity. And we will continue studying that and tracking the impacts," McCarthy told HPR.
He recently returned to West Maui to gather data to monitor the possible effects of the August 2023 fires on the reef near Lahaina.
"From initial observations, the coral cover looked pretty comparable to that pre-existing baseline data we had access to, and the reefs didn't look any different, health-wise, from elsewhere in Maui," McCarthy said.
"That's encouraging, not to say that there is no impact, because it's definitely too early to say that definitively, but I think there has been no large-scale die-off that some people were fearing."
He said it is important to continue monitoring the area because some impacts could take years, if not decades, to manifest.
This story aired on The Conversation on Aug. 13, 2024. The Conversation airs weekdays at 11 a.m. on HPR-1.
