Production of Dissolved and Particulate Hydrogen Sulfide by Marine Phytoplankton

Hydrogen sulfide is a reactive gas that in its dissolved form can be found as dissociated ions and meta-sulfide complexes, or in the particulate state as insoluble metal-sulfides. In oxygenated surface seawater the source of this hydrogen sulfide is the hydrolysis of dissolved carbonyl sulfide, but also emissions from marine phytoplankton. In this way, the phytoplankton production of hydrogen sulfide can affect the cycling of dissolved trace metals such as zinc, copper, and mercury. To examine phytoplankton production of hydrogen sulfide, four different phytoplankton species were grown in batch cultures and the concentrations of dissolved (<0.4 um) and particulate sulfide (>0.4 um) monitored over time. The chlorophyte Dunaliella produced the most hydrogen sulfide (diss>part), followed by the diatom Skeletonema (part>diss), the chryptophyte Rhodomonas (diss>part), and finally the prymnesiophyte E. huxleyi. (part>diss). Thus, all of the phytoplankton cultured emitted hydrogen sulfide, and the fact that particulate sulfide was present demonstrated that it reacts with metals to form insoluble metal sulfides, thus affecting metal cycling.