image: Because they all appear as tiny round spheres with few features to tell them apart, the symbiotic microscopic algae of corals were once thought to belong to a single species found in all reef-building corals. These symbionts are now recognized to be a group that comprises hundreds and possibly thousands of species that can be sorted into at least 15 genera. view more
Credit: Todd C. LaJeunesse
KAUST, Saudi Arabia, Thursday August 9 -- 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, and offers a glimmer of hope that at least some are likely to survive modern-day global warming as well.
"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 Dr. Voolstra, co-author and Associate Professor of Marine Science in the Red Sea Research Center at King Abdullah University of Science and Technology.
"During their long existence, they have faced severe episodes of environmental change, but thanks to their biological characteristics have managed to bounce back after each."
According to Voolstra, the micro-algae, known commonly 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 for habitat.
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, along with 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 are published online in the scientific journal Current Biology, August 9, 2018.
"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, USA.
"Accurate taxonomy [the identification and naming of species] 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."
Voolstra noted that 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.
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Other authors on the paper include; Todd LaJeunesse, Pennsylvania State University, USA; John Parkinson, Oregon State University, USA; Paul Gabrielson, University of North Carolina-Chapel Hill, USA; Hae Jin Jeong, Seoul National University, Republic of Korea; Scott Santos, Auburn University, USA; 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 King Abdullah University of Science and Technology.
Journal
Current Biology