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When corals met algae 210,000,000 years ago.

The mutually beneficial relationship between algae and modern corals--which provides algae with shelter, gives coral reefs their colors, and supplies both organisms with nutrients--began more than 210,000,000 years ago, according to a study by an international team of scientists, including researchers from Princeton (N.J.) University.

That this symbiotic relationship arose during a time of massive worldwide coral-reef expansion suggests that the interconnection of algae and coral is crucial for the health of coral reefs, which provide habitat for roughly one-fourth of all marine life. Reefs are threatened by a trend in ocean warming that has caused corals to expel algae and turn white, a process called coral bleaching.

Published in Science Advances, the study found strong evidence of this coral-algae relationship in fossilized coral skeletons dating back to the late Triassic period, a time when the first dinosaurs appeared and Earth's continents were a single land mass known as Pangea. Although symbiosis is recognized to be important for the success of today's reefs, it was less clear that that was the case with ancient corals.

"It is important to know how far back in time symbiosis evolved because it gives insight into how important symbiosis is to the health of coral reefs," says Daniel Sigman, professor of geological and geophysical sciences and a member of the Princeton Environmental Institute. "It appears that the origin of symbiosis corresponds to the rise of coral reefs in general."

In addition to confirming that symbiosis dates back to the Triassic, the study found that the corals inhabited nutrient-poor marine environments --not unlike today's subtropical waters--where algae-coral symbiosis played a major role in driving reef development.

"The onset of symbiosis with algae was highly profitable for corals," explains lead author Jarosaw Stolarski, professor of biogeology at the Institute of Paleobiology at the Polish Academy of Sciences. "It allowed them to survive in very nutrientpoor waters, and at the same time grow and expand."

Algae belonging to 1he group known as dinoflagellates live inside the corals' tissues. The algae use photosynthesis to produce nutrients, many of which they pass to the corals' cells. The corals, in turn, emit waste products in the form of ammonium, which the algae consume as a nutrient.

This relationship keeps the nutrients recycling within the coral rather than drifting away in ocean currents and can greatly increase the coral's food supply. Symbiosis also helps build reefs--corals that host algae can deposit calcium carbonate, the hard skeleton that forms the reefs, up to 10 times faster than nonsymbiotic corals

Caption: A climate scientist takes core samples from an expired coral reef.

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Title Annotation:Triassic Period
Publication:USA Today (Magazine)
Geographic Code:1USA
Date:Jun 1, 2017
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