ARSENIC CONCENTRATION AND SPECIATION IN THREE MID-ATLANTIC RIDGE HYDROTHERMAL VENT ORGANISMS

The fate of arsenic in marine environments is a topic of much discussion as this toxic metalloid is recognized to significantly bioaccumulate in aquatic organisms. In surface waters, inorganic arsenic in seawater is converted to arsenosugars by algae, which is then consumed and converted to non-toxic arsenobetaine by organisms higher in the food chain utilizing still generally unknown biosynthetic steps. However, in deep-sea hydrothermal vent environments, photosynthetic algae cannot survive—the first step of arsenic detoxification is removed. Thus these locations support ideal conditions for the study of the biosynthesis of organic arsenic compounds. In this study, we examine three species of hydrothermal vent organisms (Rimicaris exoculata, Bathymodiolus azoricus, and Branchipolynoe seepensis) for total arsenic concentration and arsenic speciation in order to further our understanding of arsenic processing and detoxification in marine systems. All three organisms have total arsenic concentrations ranging from 5-20 ppm, but their speciations are quite variable. R. exoculata contains a 2:1 mix of arsenobetaine to arsenate, while arsenic in B. azoricus and B. seepensis, both previously unstudied for arsenic concentration or speciation, is predominately arsenosugars. B. seepensis, a parasite of B. azoricus, demonstrates considerable bioaccumulation of certain organic arsenic forms. We conclude that these vent organisms are surprisingly similar in arsenic speciation to related surface water organisms, indicating that arsenic detoxification steps are common across environments with highly variable characteristics.