This research will evaluate the role of micro-organisms in the scavenging and removal of Mn in the vicinity of extended hydrothermal vent plumes. Field experiments in the northeast Pacific are planned to detect mechanisms for packaging Mn into particles and mechanisms for transporting these particles to the sediments. The sampling will be based on the conceptual model that capsuled marine bacteria package the Mn into parti- cles and that zooplankton graze the particles and repackage them in large fecal pellets that sediment rapidly to the sea floor. The biotic and abiotic Mn-removal mechanisms will be differentiated by the use of metabolic inhibitors. This work will enhance our understanding of the removal of transition- metals from seawater, our understanding of the role of biolo- gical processes in chemical transformations in seawater, and our understanding of the role of hydrothermal vents in geochemical metal cycling.
