Influence of Protozoan Grazing on the Marine Geochemistry of Particle Reactive Trace Metals.
Abstract
This thesis examines the effect of intracellular digestion by phagotrophic organisms (protozoan grazers) on the solid/liquid partitioning and speciation of strongly hydrolyzed, particle-reactive trace metals, including Fe and Th. A series of experiments was carried Out in model systems in order to determine the effect of grazer-mediated transformations on trace metals associated with cellular phases. Principle findings included mobilization of extracellular as well as intracellular trace metals by protists, apparent generation of metal-organic complexes, and decoupling of metal and carbon cycling. Studies of the effect of grazers on colloidal iron oxide (ferrihydrite) indicated that protozoan grazing can increase the dissolution rate of iron oxide phases through phagotrophic ingestion. As part of this work a novel tracer technique was 133 developed, based on the synthesis of colloidal ferrihydrite impregnated with Ba-133 as an inert tracer. This technique was shown to be a sensitive indicator for the extent of ferrihydrite dissolution/alteration by a variety of mechanisms. Using this technique, grazing by natural protistan assemblages was shown to enhance the dissolution rate of colloidal ferrihydrite over that in non-grazing controls. when integrated temporally over the euphotic zone, protozoan grazing may equal or exceed photoreduction as a pathway for iron oxide dissolution.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1998
- Accession Number
- ADA363730
Entities
People
- Katherine Barbeau
Organizations
- Woods Hole Oceanographic Institution