Contribution of Marine Phytoplankton and Bacteria to Alkalinity: An Uncharacterized Component

Abstract

The contributions of phytoplankton and bacteria cells to alkalinity (A(T)) were measured in seawater samples obtained from 205 locations including the East Sea, the North Pacific Ocean, the Bering Sea, the Chukchi Sea, and the Arctic Ocean. We attributed the differences in A(T) values measured for unfiltered versus filtered samples to A(T) components contributed by phytoplankton (retained on a 0.7 mu m filter) and by phytoplankton and bacteria combined (A(T-BIO); retained on a 0.45 mu m filter). The A(T-BIO) values reached 10-19 mu mol kg(-1) in the East Sea and the North Pacific Ocean, and progressively decreased to a level of 1 mu mol kg(-1) with distance toward the Arctic Ocean. The study shows that the A(T-BIO) values are non-negligible in coastal and open ocean environments and need to be considered when assessing the accuracy of carbon parameters calculated using the thermodynamic models that use measured A(T) as an input parameter.