The effect of protozoan grazers on the cycling of polychlorinated biphenyls (PCBs) in marine systems
Kujawinski, Elizabeth B.
MetadataShow full item record
LocationVineyard Sound, MA
Processes affecting organic carbon distribution and composition can control the speciation of organic contaminants such as polychlorinated biphenyls (PCBs) and ultimately determine their residence time in a particular environment. In marine systems, the microbial loop influences organic carbon dynamics by recycling a significant fraction of dissolved and particulate organic matter. The goal of this thesis was to understand how these recycling processes affect chlorobiphenyl (CB) cycling in marine systems by monitoring CB dynamics among organic carbon pools represented by dissolved organic matter, bacterial prey and phagotrophic protozoan grazers. Initially, I studied the extent to which a protozoan grazer (Uronema sp. - 10μm ciliate) equilibrated with aqueous PCBs within 2-3 hours. Initial calculations predicted rapid equilibration via passive diffusion. Experimentally, no difference in equilibration time was noted between grazing and non-grazing protozoa, indicating that diffusion was the primary uptake pathway for these organisms. The results were extended to determine the transition size of an organism where the rates of diffusive and ingested uptake are equivalent (100-500μm). Disassociation rate constants were estimated for complexes of CB congeners and dissolved organic carbon (DOC). CB-DOC complexes enhanced the diffusive uptake rate constant for Tenax resin and, by inference, protozoan grazers. In the second phase of this work, concentrations of surfactants, organic carbon and cells were monitored over time in protozoan cultures. The effects of bacterial growth substrate and protozoan species were examined. Surfactants increased during protozoan exponential growth while total DOC concentrations decreased. 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. Common headspace vessels were then used to compare and contrast the affinity of protozoan and bacterial culture filtrates (<0.2μm) for PCBs relative to a seawater control. Affinities were normalized to bulk DOC and surfactant concentrations to determine underlying relationships among these parameters. Values of equilibrium partition coefficients (Koc) ranged from 1046 in Vineyard Sound seawater to 105.4 and 105.5 in protist cultures, indicating that "grazer-enhanced" DOM was a better sorbent for PCBs than DOM in bacterial controls and Vineyard Sound seawater.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2000
Showing items related by title, author, creator and subject.
Involvement of Cytochrome P450 1A in the toxicity of aryl hydrocarbon receptor agonists : alteration arachidonic acid metabolism and production of reactive oxygen species Schlezinger, Jennifer J. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1998-08)Two cytochrome P4501A-dependent mechanisms of aryl hydrocarbon receptor (AhR) agonist toxicity were examined in the marine teleost scup (Stenotomus chrysops), alteration of arachidonic acid (AA) metabolism and production ...
Brownawell, Bruce J. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1986-04)Polychlorinated biphenyls (PCBs) were used as model hydrophobic organic compounds (HOC) to study physical~chemical processes which affect the speciation and fate of HOC in coastal environments. The focus of this study ...
Model of PAH and PCB bioaccumulation in Mya arenaria and application for site assessment in conjunction with sediment quality screening criteria Levine, Rachel H. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1999-06)A review of six methods for deriving sediment quality criteria SQC was conducted. Each approach was analyzed according to cost, difficulty, applicability and reliability. Results of this analysis led to the recommendation ...