Can Coral Reefs Adapt?

Picture of Coral reefs.
Coral reefs are made up of dense colonies of tiny invertebrate animals that secrete calcium carbonate to form a hard outer skeleton. Many rely on colorful, symbiotic algae that live inside their tissues for energy and nutrients.

What we know: climate change is collapsing coral reef ecosystems.

Heat stress bleaches vulnerable coral species, turning once vibrant reefs white as colorful symbiotic algae flee their coral partners. An April study by the Australian Research Council Centre of Excellence for Coral Reef Studies, published in Nature, reports that in 2016 alone, about 30 percent of the Great Barrier Reef’s corals were lost. An ocean heat wave in 2017 did yet more damage. The reef, scientists say, has changed forever.

Assistant Professor of Biological Sciences Hollie Putnam
Assistant Professor of Biological Sciences Hollie Putnam

Researchers like Assistant Professor of Biological Sciences Hollie Putnam are hoping to understand the science underlying coral resilience in the face of climate change, and why some corals seem to persist while others die. In her lab at URI, Putnam and her students are examining “assisted evolution,” specifically a form of environmental hardening that focuses on acclimation across generations. “I’m asking questions like, do offspring perform better because of their parents’ history in certain conditions, and if so, what are the mechanisms driving that?”

In a series of studies, Putnam exposed adult corals to increased temperature and acidification—both key products of climate change—and then exposed their offspring to the same conditions. “We found that there is potential for beneficial acclimatization,” she says. “There are greater survivorship and growth rates if the parents have been preconditioned.”How are the corals doing it? The answer may lie with the science of epigenetics, or changes in gene expression and function that do not involve changes in DNA. “I like to give the example that DNA is like the alphabet and some epigenetic marks are like punctuation,” Putnam says. “The gene expression—or to follow the punctuation example, the meaning of the genome—can change based on epigenetic factors.”

It’s thought that epigenetic expression may be able to cause hereditary changes in organisms, even though DNA remains unchanged, which is why Putnam’s research probes where in the coral genome the epigenetic changes take place and what this means for organism performance within a generation and across generations.

With four separate research grants taking Putnam from coral reefs in Bermuda to beaches near Seattle, and from Hawaii to French Polynesia, she’s exploring epigenetics and other forms of rapid adaptation that may help ecosystems respond to climate change. One line of inquiry focuses on West Coast geoduck clams, important marine calcifiers that seem to show more resilience if they’ve been previously exposed to short periods of adverse conditions. Another project in Hawaii examines the influence of the coral’s symbiotic algae and bacteria on epigenetics and each partner’s role in sensitivity to increased temperature and acidification.

She recognizes the urgency in her research: As questions about adaptation get answered, they will inform global conservation efforts and policy-making. “The most urgent issue is that we reduce emissions,” she says. “But if we can’t, then we need the science so that we can make hard decisions about where best to focus our limited resources for helping ecosystems persist and adapt.”