Arsenic in marine hydrothermal fluids and associated vent biota

Arsenic (As) is a unique element, in terms of its chemical und physical characteristics and ubiquitously present in the terrestrial and marine environment. Despite its well-known toxicity, several biogeochemical aspects are so far only rarely investigated and often poorly understood. Concentrations in marine hydrothermal fluids can be greatly enriched compared to seawater with the most important factors being the tectonic setting with its different physicochemical parameters like temperature, controlling phase separation processes, pH affecting As species, mobility and leaching capacity, pressure as a function of depth, the redox conditions and different adsorption and desorption reactions, as well as input of magmatic volatiles. The highest concentrations were found in island-arc setting, followed by back-arc basins and mid-ocean ridge systems and for the first time, also the presence of thioarsenates in deep-water hydrothermal systems was proven.