In situ sulfide removal and CO2 fixation rates at deep-sea hydrothermal vents and the oxic/anoxic interface in Framvaren Fjord, Norway

We have developed a technique to reproducibly measure sulfide removal rates in situ in aquatic environments, even at remote locations such as deep-sea hydrothermal vents. The technique employs the monobromobimane method for d erivatizing thiols in situ which can then later be conveniently analyzed by HPLC. The method can be applied toward a wide variety of geochemical and m icrobiological studies of sulfur cycling in aquatic habitats. Sulfide remov al rates as high as 164 mu mol/l/day and 240 mu mol/l/day were measured for hydrothermal vents at the Juan de Fuca Ridge and at the oxic/anoxic interf ace in Framvaren Fjord, Norway, respectively. These are among the highest v alues reported within the water column of any aquatic habitat. In addition, we simultaneously measured rates of microbial CO2 fixation in situ at the Galapagos and Juan de Fuca hydrothermal vents and at the oxic:anoxic interf ace of Framvaren Fjord. Rates of CO2 fixation at these sites exceeded previ ous reports and may be the result of shorter incubation times that we emplo yed. The results establish new upper limits for the rates at which these pr ocesses occur within these environments and offer interesting comparisons o f the extent of microbially mediated sulfide removal and CO2 fixation betwe en different aquatic habitats. (C) 1999 Elsevier Science B.V. All rights re served.