Vertical distribution and potential sources of strong ligands for copper(II) in the North Pacific

Complexing ability of natural organic ligands in seawater was determined by an approach based on coordination chemistry, i.e., thermodynamic calculati ons of the conditional stability constants of remarkably stable copper(II) complexes of natural ligands, which were maintained against the ligand exch ange reaction with a large excess of ethylenedianlinetetraacetic acid. Ther e exist strong ligands with the conditional stability constant of log K-Cul (.) > 14 at pH 5.71 and 4 degrees C ubiquitously in non-living dissolved or ganic matter, concentrated from both coastal and oceanic regimes. This type of ligand was detected at most depths from surface to 1,000 m in the ocean ic regimes. The same appraoch was applied to a sample of marine organism (p hytoplankton) and the strong ligand class was found out in phytoplankton. I t is suggested that phytoplankton may be one of potential sources for the s trong ligand.