Measurement of Complexing Materials Excreted from Algae and Their Ability to Ameliorate Copper Toxicity

Abstract

The complexing capacities of three algal exudates and the conditional stability constants of their copper complexes have been determined by an ion exchange method. Their ability to ameliorate copper toxicity towards the primary production of Chlorella vulgaris is related to the conditional stability constants, which regulate the ionic copper concentration. Anabaena cylindrica, Navicula pelliculosa, and Scenedesmus quadricauda excreted 6.73, 2.86, and 0.66 μmol/L of complexing ligands, respectively, with conditional stability constants of 10 7.7 , 10 8.1 , and 10 8.6 , respectively, for their corresponding copper complexes. When these constants were applied in calculations, a free copper ion concentration of 10 −10.3 mol/L was found in each exudate. Key words: algal exudates, free copper ion concentration, complexing capacity, copper ion toxicity, primary productivity