The effect of warming and acidifying oceans, caused by climate change, is already being felt on corals -- tiny stony-bodied animals that form reefs. Although coral reefs, which are formed as a result of a symbiotic relationship between corals and microscopic algae, cover less than 1 percent of the ocean floor, they support an estimated 25 percent of all marine life, making them delicate biodiversity hotspots.
Scientists have now found that certain corals are adapting to climate change and are becoming more tolerant to warmer ocean temperatures. Their findings, published Friday in the journal Science, could potentially provide a method to protect these vulnerable creatures from the mounting threat posed by global warming.
According to the study, it might be possible to save threatened coral populations by allowing them to spread their genes across oceans, particularly to areas that are likely to become hotter in future.
“Corals already have the genetic variance to adapt to changing temperature,” Mikhail Matz, an associate professor at the University of Texas at Austin and a co-author of the study, told the New York Times. “It’s just a matter of transporting these mutations from hot locations to locations that will be hot very soon because of global warming.”
To test if this heat-resistant trait is passed down genetically, scientists crossed corals from naturally warmer areas of the Great Barrier Reef in Australia with corals from a cooler latitude nearly 300 miles to the south. They found that larvae with parents from the north, where water was about 3.6 degrees Fahrenheit warmer, were more likely to survive heat stress, compared to those with parents from the south.
“We show an up to 10-fold increase in odds of survival of coral larvae under heat stress when their parents come from a warmer lower-latitude location,” the authors said in the study. “These results demonstrate that variation in coral thermal tolerance across latitudes has a strong genetic basis and could serve as raw material for natural selection.”
Corals worldwide have been badly damaged by rising sea surface temperatures, and ocean acidification, which is caused by the increased uptake of carbon dioxide from the atmosphere. This has resulted in widespread coral bleaching, wherein the symbiotic algae that corals depend on for food are wiped out or expelled.
“Our research found that corals do not have to wait for new mutations to appear. Averting coral extinction may start with something as simple as an exchange of coral immigrants to spread already existing genetic variants,” Matz said in a statement released Thursday.
While such crossbreeding would gradually occur naturally, Matz said that human intervention could speed up the process by up to 20 years.
“This is occasion for hope and optimism about coral reefs and the marine life that thrive there,” Matz said, referring to corals from species in the northern Pacific Ocean and the Caribbean Sea.