Amelioration of free copper by hydrothermal vent microbes as a response to high copper concentrations

Abstract

We examined the effect of increased copper concentrations (0–10 μM) on hydrothermal vent micro- organisms and the production of copper (Cu)-binding ligands as a response. Hydrothermal vent microbes originated from diffuse fluids at the Lilliput mussel field and the Irina II site in the Logatchev hydrothermal vent field, both on the Mid-Atlantic Ridge. Parallel studies were also conducted with amino acids supplemented to the incubations in order to verify whether dissolved amino acids, present in hydrothermal fluids, can buffer the bioavailable copper and reduce the active production of Cu-binding ligands. In all incubations, ligand concentrations increased with rising copper concentrations, but microbial cell numbers remained constant. This study shows that microbes were able to cope with as much as 10 μM dissolved copper by buffering the free copper concentration. The presence of amino acids had no significant influence on the active ligand production. Our results imply that mediation of chemical speciation by vent microbes may have an important impact on hydrothermal trace metal fluxes into the ocean.

Keywords:

• metal-binding ligands
• exudates
• voltammetry

Acknowledgements

We are grateful to captains and crews of R/V METEOR and R/V Maria S. Merian and to the ROV team of the IfM-Geomar (Kiel) for excellent cooperation and support on sea. Nicolas Rychlik is thanked for his assistance with lab work in the microbiology lab. The work was supported by grants from the Special Priority Program 1144 of the German Science Foundation titled ‘From Mantle to Ocean: Energy-, Material- and Life-cycles at Spreading Axes’. This is SPP publication no. 66. [SGS] received support via the ISAT Funding contract FRG-11-23.