“We are living in an aragonite sea”

Screen shot 2013-04-21 at 10.01.14 AMJennifer Apple

One of the benefits of conducting research at a world class facility such as Friday Harbor Labs is meeting visitors staying at the Whiteley Center. Advertised as a refuge for established scholars, it is a lovely retreat for those needing space to work. The benefit to the students is the opportunity to meet interesting people from many disciplines. While I have been here I have had the pleasure of dining with poets, writers, a philosopher and, today, a paleontologist from the University of Montana. George Stanley, Jr. is on sabbatical and is staying at the Whiteley Center for a week. He took the time out of his day to speak with our research team about sea chemistry changes and biotic consequences using ancient reef ecosystems as a model. He is the originator of the ‘naked coral hypothesis’ which states under acidic ocean conditions it may be possible for codrals to change and lose their skeleton and evolve to grow it again when the pH increases once more.

Our discussion went back in time 300 million years using the cycle of icehouse and greenhouse conditions and the changes in coral reef species due to changing the source of calcium carbonate – aragonite in icehouse conditions and calcite in greenhouse conditions. We are currently in an icehouse period and are living in an aragonite sea, according to George. Repeated patterns of perturbations in the ocean have caused coral eclipses with loss of major hypercalcifyers on reefs with delayed recovery of 1 to 10 million years. The research shows the type of calcifyer is not related to the mass extinctions, but is due to physio chemical changes in the ocean: the Ca/Mg ratio of seawater, the climate fluctuations, O2 concentrations, and the saturation state of calcium carbonate. The largest extinction event for corals occurred when the flood basalt from volcanic eruptions in the Central Atlantic magmatic province at the end-Triassic. This rapid increase in CO2 was the catalyst for these extirpations. While corals are adaptive to changes in sea chemistry and are able to evolve to form skeletons using differing forms of calcium carbonate, it was rapid changes in CO2 which lead to mass extinction events. The takeaway, for me, is that the current rise in CO2 is at an even more rapid rate than during the end-Triassic. The coral reefs are already gone in Jamaica and Florida’s will be gone by 2030. Within my children’s lifetime the coral reefs of the world may be gone, not to return for millions of years. How sad for those who come after us. Thank you, George, for an interesting discussion.


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