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How do carbon isotopes help scientists determine the age of coral reef samples?

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coral reef The Great Barrier Reef, off the coast of Queensland, Australia, is the world's largest coral reef.

Scientists determine the age of coral reef samples by analyzing the isotopic composition of their skeletons, specifically through the measurement of carbon isotopes.1

This process relies on the principles of carbon-14 dating, a method used to estimate the age of organic materials. Because corals incorporate carbon from their environment into their calcium carbonate skeletons, they become part of the global carbon cycle. While a coral is alive, it continuously absorbs carbon, including the radioactive isotope carbon-14. Once the organism dies, it stops absorbing carbon, and the amount of carbon-14 in its tissues begins to decrease at a constant, predictable rate due to radioactive decay. By measuring the residual amount of this isotope in a sample, scientists can calculate how much time has passed since the coral died.23

It is important to note that environmental factors, such as the upwelling of deep ocean water, can sometimes influence the carbon-14 levels in marine organisms, which may require calibration to ensure accurate dating.3