Diverse family of algae could help corals survive warming seas

Scientists finnd that some algae that associate with corals are much more diverse and much older than previously thought

Some corals stand a chance of surviving the current rise in global sea temperatures, a team of scientists recently reported, thanks to the diversity of their algal counterparts.

They found that the alliance with algae that underpins corals’ ability to form reefs stretches back much further than previously thought, said Todd LaJeunesse, a biologist at Pennsylvania State University and the paper’s lead author.

“Our research indicates that modern corals and their algal partners have been entwined with each other for much longer — since the time of the dinosaurs, approximately 160 million years ago,” LaJeunesse said in a statement. “During their long existence, they have faced severe episodes of environmental change, but have managed to bounce back after each one.”

LaJeunesse and scientists from the U.S., Saudi Arabia and South Korea sequenced the DNA and compared the genomes of algae called dinoflagellates that live inside corals and provide them with sustenance as they harvest sunlight to make food. The team also examined the morphological differences between members of the family using high-powered microscopes in concert with computer modeling. The specific family they looked at is called Symbiodiniaceae.

The researchers concluded that this family was much older and more diverse than previously thought.

“Presently, numerous algal lineages, called clades, are lumped into just one genus,” John Parkinson, a coral reef ecologist at Oregon State University and a co-author of the paper, said in the statement. “Using genetic techniques, we provide evidence that the family actually comprises at least 15 genera, including hundreds and possibly thousands of species worldwide.”

This diversity, combined with the family’s age, likely helped corals to begin constructing reefs on a grand scale.

“The fossil record shows that today’s reef-building corals exploded in diversity around 160 million years ago,” LaJeunesse said. “Finding that the origin of the algal symbionts corresponds to major increases in the abundance and diversity of reef-building corals implies that the partnership with Symbiodiniaceae was one of the major reasons for the success of modern corals.”

As a result of their findings, the scientists are proposing a new naming scheme for Symbiodiniaceae algae.

“Accurate taxonomy (the identification and naming of species) is a critical step in any biological research,” Parkinson said. “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.”

He pointed out that stress affected corals in different ways, and the algal species they associated with could determine their chances of bouncing back.

“[When] many corals are exposed to high temperatures they lose their symbiotic algae and die,” Parkinson said. “Others are far more tolerant of heat, and some of this resilience is based on the species of algae they have.”

Banner image of fish above a coral reef by Susann Rossbach.

Citation

LaJeunesse, T. C., Parkinson, J. E., Gabrielson, P. W., Jeong, H. J., Reimer, J. D., Voolstra, C. R., & Santos, S. R. (2018). Systematic Revision of Symbiodiniaceae Highlights the Antiquity and Diversity of Coral Endosymbionts. Current Biology.

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