Reef corals have endured since the 'age of dinosaurs' and may survive global warming

This image showcases a reef ecosystem in the Red Sea. Photo by Susann Rossbach.

The relationship between corals and the micro-algae that enable them to build reefs is considerably older and more diverse than previously assumed, according to an international team of scientists.

The team's research suggests that coral-algal partnerships have endured numerous climate change events in their long history. It also offers a glimmer of hope that at least some are likely to survive modern-day global warming.

"Our research indicates that modern corals and their algal partners have been entwined with each other since the time of the dinosaurs, approximately 160 million years ago—100 million years earlier than previously thought," said Christian Voolstra, study co-author and a KAUST associate professor of marine science in the University's Red Sea Research Center. "During their long existence, they have faced severe episodes of environmental change, but—thanks to their biological characteristics—they have managed to bounce back after each [of these]."

According to Voolstra, the micro-algae, which are commonly known as zooxanthellae, live inside the cells of corals, allowing them to acquire energy from sunlight and to build the massive, economically valuable reef formations upon which countless marine organisms rely on for a habitat.

Reef corals comprise thousands to millions of genetically identical polyps produced by clonal division. They remain attached to each other and create massive colonies, like this Orbicella. Photo by Robin T. Smith.

The team used genetic evidence including DNA sequences, phylogenetic analyses and genome comparisons to calculate the micro-algae's approximate age of origin. They also used classical morphological techniques in which they compared visual characteristics of these symbionts using light and electron microscopy, computer modeling and other methods to discover that, in addition to being older, the algae family is far more diverse than previously perceived. The results were published online in the scientific journal Current Biology (August 9).

"Using genetic techniques, we have developed an updated naming scheme that provides a new framework to identify different micro-algal symbionts," said lead author Dr. Todd LaJeunesse, associate professor of biology at Pennsylvania State University, U.S.

"Accurate taxonomy is a critical step in any biological research. This is especially true for studies attempting to understand how the partnership between reef corals and their micro-algae—which are needed for survival and growth—may adapt to climate change," LaJeunesse continued.

Voolstra noted the team has been working for close to a decade to modernize coral symbiont taxonomy in order to improve communication among scientists and advance future research on reef corals. He emphasized that discoveries like this do not change the fact that coral reefs are facing an existential threat unless action is taken to avoid climate change, but the new knowledge will enhance conservation efforts.

Other authors on the paper include: John Parkinson, Oregon State University, U.S.; Paul Gabrielson, University of North Carolina at Chapel Hill, U.S.; Hae Jin Jeong, Seoul National University, Republic of Korea; Scott Santos, Auburn University, U.S.; and James Davis Reimer, University of the Ryukyus, Japan.

This research was supported by the U.S. National Science Foundation, Pennsylvania State University, the IOC-UNESCO-World Bank, the Republic of Korea and KAUST.