Document Type


Publication Date




Publication Title

Global Biogeochemical Cycles






e2023GB007881 (1-18)


Hydrogen sulfide is produced by heterotrophic bacteria in anoxic waters and via carbonyl sulfide hydrolysis and phytoplankton emissions under oxic conditions. Apparent losses of dissolved cadmium (dCd) and zinc (dZn) in oxygen minimum zones (OMZs) of the Atlantic and Pacific Oceans have been attributed to metal-sulfide precipitation formed via dissimilatory sulfate reduction. It has also been argued that such a removal process could be a globally important sink for dCd and dZn. However, our studies from the North Pacific OMZ show that dissolved and particulate sulfide concentrations are insufficient to support the removal of dCd via precipitation. In contrast, apparent dCd and dZn deficits in the eastern tropical South Pacific OMZ do reside in the oxycline with particulate sulfide maxima, but they also coincide with the secondary fluorescence maxima, suggesting that removal via sulfide precipitation may be due to a combination of dissimilatory and assimilatory sulfate reduction. Notably, dCd loss via precipitation with sulfide from assimilatory reduction was found in upper oxic waters of the North Pacific. While dissimilatory sulfate reduction may explain local dCd and dZn losses in some OMZs, our evaluation of North Pacific OMZs demonstrates that dCd and dZn losses are unlikely to be a globally relevant sink. Nevertheless, metal sulfide losses due to assimilatory sulfate reduction in surface waters should be considered in future biogeochemical models of oceanic Cd (and perhaps Zn) cycling.


©2024. The Authors.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Data Availability

Article states: "Data used in this manuscript can be accessed from the Biological & Chemical Oceanography Data Management Office (BCO-DMO). GP16 particulate sulfide (, dissolved Zn and Cd (, thorium-234 ( and, and beryllium-7 ( GP15 total dissolved ( and and particulate sulfide ( and, dissolved Zn and Cd measured by USF (, thorium-234 (, and beryllium-7 ( Dissolved Zn and Cd data measured at TAMU will be available on BCO-DMO in the future but was not yet at the time of publication. Ocean Data View (Schlitzer, 2023) was used to produce Figures 2, 4, 9 and 10."

Original Publication Citation

Buckley, N. R., Black, E. E., Kenyon, J. A., Lanning, N. T., Sieber, M., Conway, T. M., Fitzsimmons, J. N., & Cutter, G. A. (2024). Re-evaluating hydrogen sulfide as a sink for cadmium and zinc in the oxic to suboxic upper water column of the Pacific Ocean. Global Biogeochemical Cycles, 38(3), 1-18, Article e2023GB007881.


0000-0002-1085-5833 (Buckley), 0000-0001-6744-6718 (Cutter)