Schijf, J. ., UMCES/Chesapeake Biological La, Solomons, MD, USA, schijf@cbl.umces.edu
Heyes, A. ., UMCES/Chesapeake Biological Laboratory, Solomons, MD, USA, heyes@cbl.umces.edu
Suzuki, M. T., UMCES/Chesapeake Biological Laboratory, Solomons, MD, USA, suzuki@cbl.umces.edu

EVIDENCE FOR BACTERIAL MERCURY METHYLATION AT THE OXIC/ANOXIC INTERFACE OF THE HYPERSALINE ORCA BASIN

A profile of suspended particulate matter was collected in June of 2003 across the oxic/anoxic interface of the Orca Basin, northern Gulf of Mexico. At each depth, as much as 1000-1500 L of seawater or brine was passed through an autonomous in-situ filtration device. Subsections of the frozen filters were digested for total particulate Hg analysis and extracted by distillation for particulate methyl-Hg analysis. Concentrations of these two Hg fractions, both measured by time-resolved ICP-MS, are substantially elevated at the oxic/anoxic interface. Bacterial sulfide production is confined to the same depth interval, hence most of the particulate Hg may derive from localized precipitation of Hg(II)S. Total particulate Hg concentrations within the brine are about an order of magnitude higher than in the overlying seawater. Particulate methyl-Hg concentrations are about 5% of total particulate Hg concentrations throughout the brine, whereas none could be detected in the overlying seawater. Selected filters will be analyzed for 16S rRNA genes and the presence of putative mercury-methylating bacteria. This appears to be the first report of active mercury methylation in a hypersaline anoxic environment.

Oral presentation

Presentation is given by student: No
Session #:187
Date: 03-07-2008
Time: 09:45