Effects of Protozoan Grazers on the Cycling of Polychlorinated Biphenyls (PCBs) in Marine Systems

摘要

The goal of this thesis was to understand how microbially-mediated recycling processes affect chiorobiphenyl (CB) cycling in marine systems by monitoring CB dynamics among organic carbon pools represented by dissolved organic matter, bacterial prey and phagotrophic protozoan grazers. When grazing and non-grazing protozoa were equilibrated with aqueous polychlorinated biphenyls (PCBs); no difference in equilibration time was observed, indicating that diffusion was the primary uptake pathway. The transition size of an organism where rates of diffusive and ingested uptake are equivalent was determined. Enhanced CB diffusive fluxes across the diffusive boundary layer were observed due to CB-DOC complex disassociation within this layer. Temporal dynamics of DOC, surfactants, lipo-polysaccharides and cells were monitored in protozoan cultures as a function of protozoan species and prey growth substrate. Production of surface-active material in ciliate cultures was significantly higher than in flagellate cultures, and all protozoan cultures were higher than the bacterial control. Affinities of protozoan and bacterial culture filtrates (<0.2 micrometers) for PCBs were compared relative to a seawater control.