Estimating the contribution of organic bases from microalgae to the titration alkalinity in coastal seawaters

This study reports the potential contribution of organic bases to the alkalinity of seawater samples. The con- centration of organic bases in these samples was inferred from the difference between the measured alkalinity and that calculated from a knowledge of pH and concentrations of the various inorganic acid-bases species such as total carbon, total boron, and so on. Significant concentrations of such organic bases were measured in cul- tures of the marine microalgae Rhodomonas sp. (800 µmol kg -1 ) and Isochrysis aff. Galbana (400 µmol kg -1 ), as well as in three marine environments (northern gulf of California, Mexico; San Quintin Bay, B.C., Mexico; and San Diego Bay). These three sites are characterized by significant biological activity and restricted mixing, and the organic bases were found at concentrations greater than 50 µmol kg -1 in each of these three locations.