Globally enhanced calcification across the coccolithophore Gephyrocapsa complex during the Mid-Brunhes interval

Abstract

Abstract Evolutionary or adaptative changes in Noelaerhabdaceae coccolithophores occurred in parallel with major changes in carbonate export and burial during scenarios of low orbital eccentricity, with a ~ 400 kyr recurrence, during the Pleistocene. Coeval with these conditions of enhanced proliferation, here we report a globally enhanced calcification intensity of specimens across multiple species or morphotypes within the Gephyrocapsa complex during the Mid-Brunhes (MB) interval, 400 ka. Seawater alkalinity is proposed as the environmental trigger for the increased production of both the inorganic and organic carbon, possibly implemented by a coupled increase in nutrient delivery. The strong biological pump triggered by the enhanced proliferation of highly calcified Gephyrocapsa, together with respiration dissolution, would have contributed to the associated deep sea dissolution event at the ~ 400 kyr scale, limiting the removal of alkalinity by burial, and maintaining constant levels at this scale. This new perspective highlights, first, the role of orbital forcing in phytoplankton evolution or adaptation through changes in the seawater carbon chemistry. Second, the capacity of the Noelaerhabdaceae acmes to modify the typical behavior of carbonate compensation in the ocean. Our findings suggests that changes in coccolith calcification intensity may indicate changes in past ocean carbonate chemistry and the operation of the global carbon cycle under contrasting background conditions during the Cenozoic.