While coral reefs around the world are dying from the effects of ocean acidification and global warming, one little section of the world, Kāne’ohe Bay off the windward side of Oahu, Hawaii, is defying that trend, as certain species of the corals in the bay are actually thriving.
Researchers with the University of Hawaii at Manoa are calling these corals super corals, because not only are they thriving in warm and acidic waters, the corals survived a massive sewage spill in the bay around 30 years ago. They hope that the corals offer a study for reef resilience.
“We won’t save every coral or every reef — many are already gone — but neither is it inevitable that we are going to lose all of them,” Christopher Jury, a marine biologist at the University of Hawaii, told DiscoverMagazine.com. “If we seriously reduce the rate of climate change and the intensity of local stressors, we can still give the survivors a chance.” Jury is the lead author of the study that describes how these corals are surviving one of the most heavily used and popular bays in Hawaii.
The bay suffered from dredging, coastal development and the dumping of sewage from 1930 to 1970, killing 95 percent of the bay’s corals. In 1978, the sewage outlets were relocated and the corals began to thrive again, according to the study. Between 50 percent and 95 percent of the corals recovered by 1998, in what Jury said was in waters that are warmer and more acidic than neighboring bodies of water.
“I began to realize that the temperature and chemistry conditions in Kāne’ohe Bay are very similar to the conditions that many people predict will kill corals off globally, yet the reefs in the bay seem to be thriving, making the area incredibly valuable as a possible window into the future,” Jury told DiscoverMagazine.com.
The researchers collected frags from the three dominant coral species in Kāne’ohe Bay and neighboring Waimānalo Bay: Montipora capitata, Pocillopora acuta and Porites compressa. While the bays are just 11 miles from each other, Waimānalo Bay has better reef water exchange with offshore waters than does Kāne’ohe Bay. And you would expect Waimānalo Bay corals to fare better, but in the research lab, they did not.
The coral frags were then brought into a laboratory where they were assessed for pH and temperature tolerance. The Kāne’ohe Bay corals Poc. acuta and M. capitata were more tolerant of the higher temperatures than the same species from Waimānalo Bay while Por. compressa, didn’t show any difference between the locations. Ph didn’t factor into the survival of any of the species.
The researchers also noted that the corals from Kāne’ohe Bay not only tolerated the warming water temperatures and the more acidic water of the bay, but they also grew faster than the frags taken from Waimānalo Bay.
“In contrast with many projections, we find that at least these corals do in fact harbor a lot of individual variation for temperature and chemistry tolerance and that the hardy members of the population were able to drive rapid reef recovery in Kāne’ohe Bay in spite of the warmer, more acidic conditions found there,” Jury said.
The complete paper “Adaptive responses and local stressor mitigation drive coral resilience in warmer, more acidic oceans” can be read on the Royal Society Publishing website.