To improve our understanding of how environmental mercury (Hg) concentrations influence Hg in fish, I conducted a field experiment to quantify the relative contributions of dietary and aqueous exposure to Hg levels in fish. To further assess the importance of water as a source of Hg to fish, a long-term dataset from the Mercury Experiment to Assess Atmospheric Loading in Canada and the United States was used as input data for two Hg bioaccumulation models: OneFish (accumulation from food and water) and Wisconsin (accumulation from food). Both approaches used enriched stable isotopes of Hg. Yellow perch accumulated 10-21% of their Hg directly from water. Wisconsin model predictions were significantly lower than observed fish Hg concentrations and OneFish predictions. These results suggest that waterborne Hg is an important contributor to Hg in fish and that the exclusion of water in bioaccumulation models may produce underestimates of fish Hg concentrations.

To improve our understanding of how environmental mercury (Hg) concentrations influence Hg in fish, I conducted a field experiment to quantify the relative contributions of dietary and aqueous exposure to Hg levels in fish. To further assess the importance of water as a source of Hg to fish, a long-term dataset from the Mercury Experiment to Assess Atmospheric Loading in Canada and the United States was used as input data for two Hg bioaccumulation models: OneFish (accumulation from food and water) and Wisconsin (accumulation from food). Both approaches used enriched stable isotopes of Hg. Yellow perch accumulated 10-21% of their Hg directly from water. Wisconsin model predictions were significantly lower than observed fish Hg concentrations and OneFish predictions. These results suggest that waterborne Hg is an important contributor to Hg in fish and that the exclusion of water in bioaccumulation models may produce underestimates of fish Hg concentrations.

The cyanobacterially synthesized non-canonical amino acid β-N-methylamino-ʟ-alanine (BMAA) has been proposed to be a causative agent in the development of sporadic neurodegenerative diseases. This neurotoxin bioaccumulates and biomagnifies with increasing trophic levels in ecosystems by associating with proteins. It has been suggested that these associations with host proteins also serve as a reservoir from where BMAA is slowly released with normal protein catabolism, resulting in a continuous low level exposure. However, the nature of these associations remains poorly defined. The widely accepted hypothesis regarding the nature of these associations is that BMAA associates with proteins through primary incorporation into proteins with specific replacement of serine. In addition to excitotoxicity, BMAA misincorporation has been proposed as a potential mechanism of toxicity because of its link to protein tangle diseases. Interactions between BMAA and proteins that are not the result of misincorporation, have also been observed. However, the nature of these non-primary associations has not been investigated. This study focussed on establishing whether BMAA is misincorporated into host proteins with consequent toxicity, and on elucidating the nature of the BMAA-protein associations not linked to primary incorporation. In comparative studies between BMAA and canavanine, an arginine analogue known to misincorporate, exposure to BMAA did not result in any toxicity in prokaryotes or in an undifferentiated eukaryotic mammalian cell line, in contrast to what was observed upon canavanine exposure. Differentiation of the cell line with nerve growth factor to express glutamate receptors resulted in marked toxicity upon BMAA exposure, highlighting excitoxicity as the main mechanism of BMAA toxicity. Furthermore, it was demonstrated that BMAA interacts with free amino acids and proteins in the absence of de novo protein synthesis, causing enzyme inhibition and protein misfolding. It was concluded that BMAA does not interact with proteins through primary incorporation and that the observed associations are the result of an interaction between BMAA and amino acid side chains to form covalent bonds.

No description available.

The "equilibrium partitioning theory" is one of the most widely used models to evaluate the bioavailability of sediment-associated, nonpolar, organic contaminants and it makes specific assumptions regarding the factors that influence this bioavailability. The objective of this research was to test two assumptions of this theory: (1) that benthic organisms are exposed to a constant, equilibrium-predicted concentration of a contaminant in interstitial water, regardless of the behavior of the organism; and (2) that exposure to interstitial water in a sediment exposure system is equivalent to the exposure in a water-only exposure system. The effect of behavior on the exposure to sediment-associated phenanthrene was tested by exposing three marine amphipod species (with different burrowing behaviors) to the polycyclic aromatic hydrocarbon (PAH) phenanthrene under two exposure conditions, one with spiked sediment and clean overlying water and the other with spiked sediment and contaminated overlying water. This was done to evaluate the extent to which the burrow irrigating behavior and the different tube or burrow building behavior exhibited by the amphipod species could effect the accumulation of sediment-associated phenanthrene. The assumption of equivalent exposure between sediment and water systems was tested by exposing the amphipods to the same concentration of phenanthrene in a water-only versus sediment exposure system. In both series of experiments, the bioaccumulation of phenanthrene by the amphipods was followed over 72 hours and bioaccumulation kinetics calculated for each species and exposure treatment. The results indicated that the burrow irrigating behavior of benthic marine amphipods can significantly affect the exposure of these amphipods to sediment-associated contaminants by diluting the concentration of contaminant in the interstitial water surrounding the organisms with overlying water. Additionally, there was a species dependent decrease in exposure based upon the tube or burrow building strategy used by the amphipod species. The results also indicated that exposure in a sediment system was not equivalent to exposure in a water-only system. The bioaccumulation of phenanthrene was significantly higher for all three species in water versus sediment. However, the interpretation of the results from this second series of experiments was complicated by the degradation of phenanthrene in the sediment-only exposure. / Graduation date: 1998

The active synthetic constituent of oral contraceptives 17α- ethinylestradiol (EE2) and its natural steroidal estrogen analogues are being released into the aquatic environment mainly via wastewater treatment plants (WWTPs). Although steroidal estrogens have been frequently reported in very low concentrations in the environment, they have been placed at the top of the list of endocrine disrupting chemicals (EDCs) for their high estrogenic activity in non-target aquatic species like fish and frogs. Almost 30 years worth of intensive research has moved the problem of endocrine disruption in the aquatic environment from being a hypothesis to a well-known cause-and-effect story. However, the fate and effects of many pharmaceuticals, including EE2, remain poorly understood. Thus, the main objective of this thesis was to investigate EE2 bioaccumulation in fish by field and laboratory studies. An optimized sample preparation and analytical method protocol was achieved to detect EE2 in its biologically active form in whole fish tissue at trace levels (ng/g). Shorthead redhorse suckers (ShRHS) (Moxostoma macrolepidotum) collected in proximity to a WWTP in the St. Clair River have significantly accumulated EE2 with an average of 1.5 ng/g. EE2 bioaccumulation was limited to fish exhibiting intersex and with induced vitellogenin (VTG). EE2 was absent in fish from a reference site. Positive correlations between EE2 and lipid content as well as "15N supported the hypothesis of EE2 bioaccumulation in wild ShRHSs. A wider survey was carried out to explore patterns of EE2 bioaccumulation in the pelagic and benthic food-wed of the St. Clair IV River, Ontario. In the WWTP effluents and nearby surface waters, EE2 levels were extremely low and below our method detection limits. All of the seven sampled species from different trophic levels and the sediment samples collected from the impacted sites and the reference sites did not have any measurable EE2 concentrations. A laboratory controlled study where male goldfish (Carassius auratus) were exposed to EE2 via water versus food demonstrated that fish can rapidly accumulate EE2 by both routes of exposure. The uptake constant for water was 45 h-1 and the bioconcentration factor for EE2 in fish was 377. The fast uptake rate of EE2 via water coincided with a much slower elimination rate constant of 0.0786 h-1. The assimilation efficiency of 0.106 for EE2 by goldfish was determined by EE2 dietary exposure, which was used to predict EE2 accumulation under different exposure scenarios. The work presented here was the first demonstration of EE2 bioaccumulation in wild fish and the first to model EE2 bioaccumulation from water and dietary exposure in laboratory-exposed fish.

The active synthetic constituent of oral contraceptives 17α- ethinylestradiol (EE2) and its natural steroidal estrogen analogues are being released into the aquatic environment mainly via wastewater treatment plants (WWTPs). Although steroidal estrogens have been frequently reported in very low concentrations in the environment, they have been placed at the top of the list of endocrine disrupting chemicals (EDCs) for their high estrogenic activity in non-target aquatic species like fish and frogs. Almost 30 years worth of intensive research has moved the problem of endocrine disruption in the aquatic environment from being a hypothesis to a well-known cause-and-effect story. However, the fate and effects of many pharmaceuticals, including EE2, remain poorly understood. Thus, the main objective of this thesis was to investigate EE2 bioaccumulation in fish by field and laboratory studies. An optimized sample preparation and analytical method protocol was achieved to detect EE2 in its biologically active form in whole fish tissue at trace levels (ng/g). Shorthead redhorse suckers (ShRHS) (Moxostoma macrolepidotum) collected in proximity to a WWTP in the St. Clair River have significantly accumulated EE2 with an average of 1.5 ng/g. EE2 bioaccumulation was limited to fish exhibiting intersex and with induced vitellogenin (VTG). EE2 was absent in fish from a reference site. Positive correlations between EE2 and lipid content as well as "15N supported the hypothesis of EE2 bioaccumulation in wild ShRHSs. A wider survey was carried out to explore patterns of EE2 bioaccumulation in the pelagic and benthic food-wed of the St. Clair IV River, Ontario. In the WWTP effluents and nearby surface waters, EE2 levels were extremely low and below our method detection limits. All of the seven sampled species from different trophic levels and the sediment samples collected from the impacted sites and the reference sites did not have any measurable EE2 concentrations. A laboratory controlled study where male goldfish (Carassius auratus) were exposed to EE2 via water versus food demonstrated that fish can rapidly accumulate EE2 by both routes of exposure. The uptake constant for water was 45 h-1 and the bioconcentration factor for EE2 in fish was 377. The fast uptake rate of EE2 via water coincided with a much slower elimination rate constant of 0.0786 h-1. The assimilation efficiency of 0.106 for EE2 by goldfish was determined by EE2 dietary exposure, which was used to predict EE2 accumulation under different exposure scenarios. The work presented here was the first demonstration of EE2 bioaccumulation in wild fish and the first to model EE2 bioaccumulation from water and dietary exposure in laboratory-exposed fish.

This thesis describes studies and research conducted as part of the development, standardization, and validation of a new laboratory protocol for measuring the bioaccumulation of sediment-associated contaminants in freshwater organisms. The test species used in this method are the oligochaete Lumbriculus variegatus, the mayfly nymph Hexagenia spp., and the juvenile fathead minnow Pimephales promelas. Bioaccumulation methods in the literature were critically reviewed to properly guide the development and standardization of methods. This enabled data gaps to be addressed and the conditions and exposure techniques of the new method to be standardized, properly justified, and based on experimental evidence. Method development included the investigation of the effect of the density of organisms on bioaccumulation in the three test species. The importance of standardizing loading density to total organic carbon (TOC) in sediment was demonstrated, as was the appropriateness of using a ratio of TOC to organism dry weight of 27:1 as a standard loading density for the different test species. To validate the new method and assess the relative effectiveness of the three test species for accumulating different contaminants, a variety of field-contaminated sediments were tested, representing a range of contaminants, levels of contamination, and physical properties of sediment. It was observed that differences in bioaccumulation between the three species may, but do not always, exist, and can vary with contaminant and sediment type. It was also demonstrated that estimates of bioaccumulation, such as biota-sediment accumulation factors (BSAFs), can be species- and site-specific, supporting the need and use of standardized bioaccumulation methods and test species to facilitate comparisons across sites or over time. Comparisons of laboratory- and field-based estimates of bioaccumulation further validated the new laboratory method. Good agreement was observed between laboratory and field estimates for fish, while bioaccumulation was higher in laboratory-exposed invertebrates compared to mussels caged in situ. The laboratory method generally overestimated the relative bioavailability of contaminants compared to the field, but provides a conservative estimate of bioaccumulation. A kinetic study investigated the uptake and elimination of PCBs in the three test species and demonstrated that a 28-d test duration was a sufficient standard for both invertebrate species to reach steady-state concentrations. There was conflicting evidence of whether steady-state concentrations were truly reached in the fish and uncertainty remains as to the appropriateness of a 28-d test for these organisms, for which additional testing is necessary.

The active synthetic constituent of oral contraceptives 17α- ethinylestradiol (EE2) and its natural steroidal estrogen analogues are being released into the aquatic environment mainly via wastewater treatment plants (WWTPs). Although steroidal estrogens have been frequently reported in very low concentrations in the environment, they have been placed at the top of the list of endocrine disrupting chemicals (EDCs) for their high estrogenic activity in non-target aquatic species like fish and frogs. Almost 30 years worth of intensive research has moved the problem of endocrine disruption in the aquatic environment from being a hypothesis to a well-known cause-and-effect story. However, the fate and effects of many pharmaceuticals, including EE2, remain poorly understood. Thus, the main objective of this thesis was to investigate EE2 bioaccumulation in fish by field and laboratory studies. An optimized sample preparation and analytical method protocol was achieved to detect EE2 in its biologically active form in whole fish tissue at trace levels (ng/g). Shorthead redhorse suckers (ShRHS) (Moxostoma macrolepidotum) collected in proximity to a WWTP in the St. Clair River have significantly accumulated EE2 with an average of 1.5 ng/g. EE2 bioaccumulation was limited to fish exhibiting intersex and with induced vitellogenin (VTG). EE2 was absent in fish from a reference site. Positive correlations between EE2 and lipid content as well as "15N supported the hypothesis of EE2 bioaccumulation in wild ShRHSs. A wider survey was carried out to explore patterns of EE2 bioaccumulation in the pelagic and benthic food-wed of the St. Clair IV River, Ontario. In the WWTP effluents and nearby surface waters, EE2 levels were extremely low and below our method detection limits. All of the seven sampled species from different trophic levels and the sediment samples collected from the impacted sites and the reference sites did not have any measurable EE2 concentrations. A laboratory controlled study where male goldfish (Carassius auratus) were exposed to EE2 via water versus food demonstrated that fish can rapidly accumulate EE2 by both routes of exposure. The uptake constant for water was 45 h-1 and the bioconcentration factor for EE2 in fish was 377. The fast uptake rate of EE2 via water coincided with a much slower elimination rate constant of 0.0786 h-1. The assimilation efficiency of 0.106 for EE2 by goldfish was determined by EE2 dietary exposure, which was used to predict EE2 accumulation under different exposure scenarios. The work presented here was the first demonstration of EE2 bioaccumulation in wild fish and the first to model EE2 bioaccumulation from water and dietary exposure in laboratory-exposed fish.

Traditional assessments of contaminated sites require the collection and analysis of field media. Specifically, sediment analysis is used to determine type of contaminant as well as total contaminant concentrations (TCC). Although TCC can be used to determine if a site is contaminated, it is unable to adequately predict exposure and bioaccumulation in organisms. Biota-sediment accumulation factors were originally introduced to calculate and predict expected exposure to organisms based on sediment TCC. As they have been shown to be unreliable with field sediments, their use is limited. Alternatively, Tenax has been examined as a tool for measuring exposure to hydrophobic organic contaminants, where the Tenax extractable concentration is related to the bioaccumulated organism concentration. Although this relationship has been demonstrated in multiple studies, few have actually related the data from multiple sites to develop a standard model of Tenax accumulation. This research had two specific goals: Develop a literature based model of Tenax accumulation of polychlorinated biphenyl congeners (PCBs) and test it's applicability to field collected sediments from the Ottawa River (OR, Toledo OH, Chapter 2) and verify the use of the model in a highly-disturbed, post-dredge system, as well as the use of Tenax as an indicator of changes in bioavailability after dredging (Chapter 3). The literature-based complete Tenax model (TM) provided a strong model for the prediction of bioaccumulation in Lumbriculus variegatus (r2=0.91). When compared to the pre-dredge data from the OR, 95% of the data were encompassed by the CTM. No bias of the model was observed across homologue groups. Subsequently, the model was used with sediments collected after remediation via dredging from the OR. In this study, the CTM encompassed 73% of the data. Although all sites along the river were considered disturbed by the dredging, resuspension, and drift of sediments, data from sites that were less disturbed were better described by the model (86% versus 64% of dredged data). Overall, the CTM is recommended for use in the prediction of exposure and accumulation of PCBs in field sediments.