Dissolved copper, copper-binding ligands and dissolved organic carbon (DOC) in deep-sea pore waters of the Pacific Ocean

The bioavailability and thus toxicity of Cu is strongly influenced by its speciation which is dominated by organic ligand (L) complexation in seawater, with L-complexes being considered less bioavailable than free Cu2+. The presence of CuL-complexes in deep-sea sediments has, however, not been systematically studied in the context of deep-sea mining.

We thus analyzed the dissolved Cu concentration ([dCu]), Cu-binding L concentration ([L]) and DOC concentration in deep-sea pore waters of two polymetallic nodule provinces in the Pacific Ocean, the Peru Basin and the Clarion-Clipperton-Zone. We compared undisturbed sites with 26-year-old disturbance track sites and one 5-week-old site where a small sediment plume resettled.