Sources, sinks, and cycling of dissolved organic copper binding ligands in the ocean

Abstract

AbstractOrganic Cu-binding ligands have a fundamental influence on Cu distributions in the global ocean and they complex >99% of the dissolved Cu in seawater. Cu-binding ligands however, represent a large diversity of compounds with distinct sources, sinks and chemical properties. This heterogeneity makes the organic Cu-binding ligand pool difficult to study at the global scale. In this review, we provide an overview of the diversity of compounds that compose the marine Cu-ligand pool, and their dominant sources and sinks. We also summarize the most common analytical methods to measure ligands in marine water column samples. Generally, ligands are classified according to their conditional binding strength to Cu. However, the lack of a common definition for Cu ligand categories has previously complicated data intercomparison. To address this, we provide a general classification for Cu-binding ligands according to their binding strength and discuss emerging patterns in organic Cu-binding ligand distributions in the ocean according to this classification. To date, there is no global biogeochemical model that explicitly represents Cu ligands. We provide estimates of organic Cu-binding ligand fluxes at key interfaces as first order estimates and a first step for future modeling efforts focused on Cu and Cu-binding ligands.