A New Approach to Estimating Coccolithophore Calcification Rates From Space

Abstract

The production and ultimate fate of calcium carbonate in the global ocean has implications for the efficiency of the biological carbon and alkalinity pumps. Historically, sediment trap flux data and/or mass balance equations have been used to estimate the rate of particulate inorganic carbon production in the ocean. More recently, satellite data have been used to provide a more comprehensive global overview of this important biogeochemical process based on relationships determined from multilinear regression of measured calcification rates against a number of measurable variables. Here we describe a simple model to estimate calcification rate based around elements of coccolithophore physiology that can be easily parametrized with satellite ocean color data. The model output conforms to our understanding of the spatial and temporal distribution of coccolithophores and performs relatively well at reproducing global rates that are of the correct order of magnitude, while capturing the variability in such a complex, natural process when compared to field calcification rate measurements (slope = 0.98; R2 = 0.28; p < 0.05; RMSE = 0.53 mg C · m−3 · day−1). Average, global, euphotic zone depth-integrated calcification rate is estimated to be 1.42 ± 1.69 Pg particulate inorganic carbon/year with the oceanic gyres contributing the greatest influence.