Isotopic composition in ancient algae confirms atmospheric cooling 6 million years ago

An interesting article in the journal Nature  by H.M Stoll and C Bolton of the University of Oviedo, Spain,   publishes their findings on the discovery of  low levels of CO2  in ancient algae in the late Miocene period and discusses the implications for climate change and ocean ecology. Coccolithophores are unique in that they use carbon for both photosynthesis and calcification.  They develop a new inverse model of carbon allocation in the cell, driven by the isotopic composition of carbon in the calcite and organic matter, and show that when carbon dioxide levels are low, coccolithophorids in culture reallocate HCO3- from photosynthesis to calcification.  This provides the first evidence that competition between photosynthesis and calcification is widespread and occurs in several different species. 

This adaptation arose in the latest Miocene in response to the crossing of a critical threshold in dissolved CO2 in the ocean, which they infer to result from decreasing atmospheric CO2.  Such a decrease is consistent with widespread evidence for cooling over that time interval.

Nu Instruments’ Perspective IRMS with Nu Carb automated carbonate device were used for this research. 

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