Experimental assessment of microbial effects on chemical interactions between seafloor massive sulfides and seawater at 4ºc

To assess the effects of microbes on the exchange of Cu, Zn, and P between seafloor massive sulfide (SMS) deposits and seawater, we monitored the variation of the concentrations of Cu, Zn, and P in the artificial seawater of reaction systems that did or did not also include slabs and microbes originating from an SMS sample at 4ºC for 71 days. Dissolution of Cu and Zn from the slabs was observed when microbes were present or absent. Zinc from the slabs dissolved 1.4–2.3 fold more rapidly when microbes were present. In the presence of slabs and microbes, the rate of removal of P from the artificial seawater was the sum of the individual removal rates associated with the slabs and microbes. Six bacterial phylotypes including Halomonas and Marinobacter were present at the end of the experiment as shown by PCR-based analysis targeting 16S rRNA genes. These bacteria probably contribute to the release of Zn from the SMS slab and removal of P from the artificial seawater. Our results provide further insights into the role(s) of microbes on the geochemical interactions between SMS deposits and seawater.