Genetics Could Help Protect Coral Reefs From Global Warming

Coral reefs are dying at an alarming rate as water temperatures rise worldwide as a result of global warming, pollution, and human activities. In the past three decades, half of Australia’s Great Barrier Reef has lost its coral cover.

A new Columbia University study provides more evidence that genetic sequencing may reveal evolutionary differences in reef-building corals that could one day help scientists identify which strains could adapt to the warmer seas.

The findings, published in Science On July 17, provide a window into genetic processes that allow some corals to withstand dramatic climate changes that could complement or enhance current conservation efforts.

“We need to use as many tools as possible to intervene, or we will continue to see coral reefs disappear,” said Zachary Fuller, a postdoctoral researcher in biology at Columbia and first author of the study. “The use of genomics can help identify which corals have the ability to live at higher temperatures and reveal genetic variants associated with climate resilience.”

Found throughout the world in tropical oceans, coral reefs are one of the most diverse and valuable ecosystems on Earth. They are actually important and living animal colonies for many reasons. Reefs provide a habitat for a wide variety of marine species; protect the coasts from storms, floods and erosion; and help support the fishing and tourism industries.

In the late 1990s, reefs around the world experienced their first wave of mass bleaching, which occurs when high water temperatures destroy the symbiotic relationship with the colorful algae of a colony, causing corals to become white. Loss effectively starves them, as corals rely on photosynthetic algae that live in their tissues for nutrients. Reefs can recover from bleaching, but prolonged periods of environmental stress can eventually kill them.

Columbia research predicts, to some degree, which corals can withstand unusually high temperatures and withstand bleaching events.

“Genomics allows us to examine genetic differences that could influence survival and bleaching tolerance, which helps us determine how we might support coral health,” said Molly Przeworski, professor in the Departments of Biological Sciences and Biology Systems at Columbia and lead author of the study.

To collect their genetic data, Fuller, Przeworski and their collaborators from the Australian Institute of Marine Sciences analyzed 237 samples collected at 12 locations along the Great Barrier Reef, generating the highest quality coral sequences to date. The sequence allowed the researchers to search for signatures in the genome where the adaptation occurred and find genetically distinct variations associated with tolerance to bleaching.

“What we discovered is that no single gene was responsible for differences in a coral’s response to bleaching, but that many genetic variants influence the trait,” said Fuller. “On their own, each has a very small effect, but when taken together we can use all of these variants to predict which corals can survive against the warmer seas.”

Fuller and Przeworski said the findings offer a way for coral biologists to search for more strains that can better cope with ocean warming and allow similar approaches that can be used in other species more exposed to climate change.

“The best opportunity we have to save what remains of the Earth’s coral reefs is to mitigate the effects of climate change by rapidly reducing greenhouse gas emissions,” said Fuller. “Meanwhile, genetic approaches can buy us time.”