<p>In the Anthropocene, amphibians must not only cope with natural stressors but also a suite of human-made stressors that have been experienced relatively recently within their evolutionary history. Because it has become increasingly common for natural and anthropogenic stressors to co-occur in aquatic ecosystems, the study of their separate and combined effects on ecosystems and their component species is increasingly necessary. This is especially important for amphibians, which have experienced global declines and can be highly sensitive to both natural and anthropogenic stressors. Pesticides and parasites are two commonly co-occurring stressors that can have complex individual and synergistic detrimental effects in amphibian populations. Here, I conducted three studies to broadly assess the separate and interactive effects of pesticides and parasites on amphibians. More specifically, I explored: 1) the underlying physiological mechanism allowing amphibians to induce increased tolerance to a pesticide within a single generation, 2) the effects of exposure timing to two functionally similar cryptic parasite species on infection outcomes, and 3) population-level variation in susceptibility to parasites and whether prior exposure to pesticides influenced the outcome of host-parasite interactions. First, to test the hypothesis that induced pesticide tolerance is the result of a generalized stress response, I exposed tadpoles to an anthropogenic stressor (sublethal pesticide dose), a natural stressor (cues from a caged predator), or a simulated stressor via exogenous exposure to the stress hormone corticosterone (CORT). I then exposed the larvae to a lethal carbaryl treatment to assess how the stressor exposures influenced survival. I found that prior exposure to exogenous CORT and predator cues induced tolerance to a lethal concentration of carbaryl, providing evidence that pesticide tolerance can be induced by a generalized stress response both in the presence and absence (exogenous CORT) of specific cues. Second, I explored how the timing of host exposure to two co-occurring cryptic echinostome species influences infection outcomes. I found that echinostome infection success in larval anurans can differ significantly based on the parasite species makeup, density, and exposure timing. I also found that priority effects can occur even between functionally similar cryptic species, with an early exposure to <i>Echinoparyphium </i>lineage 3 reducing the infection success of <i>Echinostoma trivolvis </i>three days later. Finally, I assessed the influence of pesticide exposure on host-parasite interactions and population-level variation in these responses. This was accomplished by exposing wood frog larvae from eight populations to one of two treatments (a sublethal carbaryl concentration or a pesticide-free control) followed by controlled parasite exposures to either echinostome trematodes or ranavirus. Then, I assessed how pesticide exposure influenced infection loads, infection prevalence, and survival in each population. I found significant population-level variation in infection outcomes. Interestingly, however, I found no significant effects of pesticide exposure on disease outcomes. Together, these three studies demonstrate the wide-ranging and surprising outcomes that can result from interactions among and between natural and anthropogenic stressors.</p>

A process for disposing of pesticide rinsewater generated from the rinsing of application equipment is being developed at Virginia Polytechnic Institute and State University. This process involves the sorption of pesticides onto an organic matrix followed by degradation in a composting environment. We are now evaluating the hazards that might be associated with land-applying composted pesticide waste. Diazinon was the first pesticide selected for evaluation, which consisted of two studies. The first used the earthworm species Eisenia foetida to evaluate the toxicity of soil amended with composted diazinon waste. The second study determined the bioavailability of delta-2-14C-diazinon and its degradation products to E. foetida in soil amended with composted delta-2-14C-diazinon. Results from the first study indicate that uncomposted diazinon sorbent and 30-day composted diazinon sorbent were toxic to E. foetida at sublethal and lethal levels. However, E. foetida exposed 60-day composted diazinon sorbent did not experience mortality or demostrate sublethal effects commonly associated with acetylcholinesterase inhibition. Earthworms exposed to diazinon that was uncomposted or composted for 30 days in the radiolabelled study experienced higher mortality than in the field study. After 30 and 60 days of composting 14C-diazinon became unextractably incorporated into organic matter and very little was mineralized. Earthworms were shown to accumulate radioactivity when exposed to soil amended with 60- day composted delta-2-14C-diazinon. The majority of this radioactivity was unextractably bound to earthworm tissue and that which was extractable contained only trace levels of delta-2-14C-diazinon. Based on the absence of toxicity in the field study and the low levels of 14C-diazinon present in earthworm tissues, 60 days of composting appears to greatly reduce the hazard that diazinon rinsate poses to E. foetida. / Master of Science

Las angiospermas marinas son organismos esenciales para los ecosistemas costeros de zonas templadas. Sostienen una amplia diversidad biológica, regulan la dinámica sedimentaria costera y capturan grandes cantidades de carbono atmosférico. Sin embargo, a pesar de los servicios ecosistémicos que proporcionan, se encuentran amenazadas por actividades humanas y, especialmente, por la contaminación marina. Para conservar las praderas de angiospermas marinas es necesario desarrollar herramientas de seguimiento a todos los niveles de organización biológica que permitan detectar el estrés fisiológico para prevenir la regresión de estos valiosos hábitats, o de determinar la magnitud de estos procesos a gran escala. Es por ello que se plantea esta tesis con el objetivo de determinar el grado de afección de los vertidos de salmuera procedente de plantas desaladoras, además de su interacción con otros estresores ambientales, desde la escala molecular (expresión de genes) hasta la poblacional (cobertura de las praderas). Estos análisis podrán permitir la selección de biomarcadores específicos que sirvan como indicadores de alerta temprana de estrés y puedan permitir la toma de medidas de gestión para conservar. Los capítulos 2 y 3 de la tesis mostraron, por un lado, una estabilidad general de las praderas someras de la angiosperma marina Posidonia oceanica en la provincia de Alicante y, por otro, una grave regresión de la pradera en la bahía de la ciudad de Alicante. Esto se debe a la coexistencia de diversos impactos ambientales en esa zona que son responsables de esta pérdida de cobertura (619 hectáreas desde 1984), a pesar de la estabilidad general de estas praderas a mayor escala. De esta forma se puede determinar que los procesos de declive de estos ecosistemas no se produce de forma global y generalizada sino a escala local y, por tanto, las herramientas de gestión deben enfocarse en una menor escala espacial y atendiendo a los estresores específicos de cada zona. En el capítulo 4 se sometió a la angiosperma marina Zostera chilensis (endémica del Pacífico sudamericano) a incrementos de salinidad (+3 y +6 practical salinity units, psu) con sales artificiales para determinar su respuesta y tolerancia a potencial vertido de salmuera. La planta mostró una reducción fotoquímica una producción de peróxido de hidrógeno y una sobreexpresón de genes relativos a la osmorregulación y el estrés oxidativo. La respuesta etabólica fue similar a ambos incrementos de salinidad, pero la mayor producción de peróxido y de enfriamiento no fotoquímico a +6 psu parecen indicar que esta salinidad está por encima del umbral de tolerancia de la planta, y por tanto que podría ser vulnerable a un in. En los capítulos 5, 6 y 7 se aplicaron distintos incrementos de salinidad a P. oceanica (desde +2 hasta +6 psu) con salmuera real de una planta desaladora, tanto en condiciones de laboratorio como de terreno (frente a vertido de una planta desaladora) y midiendo respuestas metabólicas tanto en hojas como en meristemos apicales. La salmuera mostró incrementar ciertos indicadores de estrés comparado con sales artificiales y la producción de peróxido de hidrógeno, la peroxidación de lípidos y la expresión de genes relacionados con el estrés osmótico y oxidativo fueron superiores en condiciones naturales (terreno). Además las respuestas fueron más claras en los meristemos apicales en comparación con las hojas. Todos estos resultados indican que los vertidos de salmuera en interacción con los factores naturales ambientales pueden genera un mayor estrés metabólico y fisiológico, que además se puede medir más claramente en los meritemos que en las hojas. El uso de biomarcadores moleculares y bioquímicos en praderas expuestas a vertidos de salmuera, puede permitir la detección temprana de estrés y la potencial interacción con otros factores ambientales (naturales o antrópicos) que puedan comprometer la fisiología y la supervivencia de la planta. Por tanto estos indicadores tienen el potencial de usarse, en combinación con indicadores fenológicos o poblacionales, en planes de seguimiento para medir el grado de afección de un estresor. En esta tesis se proponen una serie de biomarcadores específicos al estrés generado por la salmuera con el fin de desarrollar medidas de gestión costera específicas a escala local que puedan detectar el impacto ambiental y prevenir la degradación de estos ecosistemas marinos. / Tesis financiada por la convocatoria UAFPU98 del programa propio del Vicerrectorado de Investigación de la Universidad de Alicante.

No description available.

Annually, it is estimated that 82 million tons of global plastic waste is either mismanaged or littered, bypassing waste management practices. This mismanagement causes the permeation of plastic debris into the environment, which then undergoes natural degradation processes. These degradation processes result in the proliferation of miniscule plastic particles known as microplastics. Due to the inherent proximity to sources of anthropogenic waste, concerns of microplastic pollution and its impact on freshwater ecosystems have recently increased. Until recently, microplastic research has primarily been focused on the toxicological affects felt by an individual organism rather than the intricate interactions that occur between taxa. Only focusing on the individual toxicological impact turns a blind eye on the communities that maintain ecosystem health and stability. To that end, our experiment was unique as it will be the first study assessing the impact of a freshwater symbiosis, as symbioses in the scope of toxicokinetic studies have primarily been dominated by that of terrestrial and marine relationships. This knowledge gap is a serious concern as its argued freshwater systems are more contaminated, than that of other aquatic habitats. To address this knowledge gap, we conducted mesocosm-based exposure-response assays, exposing the crayfish-branchiobdellidan symbiosis to microplastics of fibrous, microsphere, and tire wear particle morphologies while varying symbiont densities. We used the crayfish-branchiobdellidan model system in our study due to its amenability to laboratory monitoring and manipulation. The crayfish C. appalachiensis, common in the Virginia New River Basin, served as hosts to obligate ectosymbiotic annelids in the order Branchiobdellida. Previous research, using the crayfish-branchiobdellidan symbiosis demonstrated that the interaction is a cleaning symbiosis, where hosts benefit from reduced gill fouling while symbionts benefit from increased resource availability. We observed the physical and behavioral changes of the crayfish-branchiobdellidan symbiosis over a 172-day chronic exposure assay. Our results show, crayfish hosts with higher symbiont densities experienced decreased physical growth when exposed to microplastics compared to the control. This alteration in host growth was the result of increased antagonistic symbiont behavior in the form of gill tissue consumption. Our results suggest microplastics caused a reduction in epibiont abundance, thus decreasing symbiotic resource availability. This reduction in resources resulted in a shift of context dependency, thus increasing parasitic symbiont behavior. This study demonstrates microplastics have the capability to shift symbiotic context from a mutualism to a parasitism. / Master of Science / Every year, due to improper waste management, approximately 82 million tons of global plastic waste ends up in the environment. Once in the environment, this plastic waste naturally breaks down into tiny particles known as microplastics. Recently, there's been growing concern about how these microplastics affect freshwater habitats. One particular worry is the impact that this contaminant can have on the relationships between different organisms living in freshwater environments. Currently, multiple scientific experiments have studied the effects of microplastics on marine and land-based organismal relationships, however, none have studied the effect of microplastics on freshwater organismal relationships. To explore this, we used the relationship of crayfish and a type of worm called Branchiobdellida, due to their close, prolonged relationship commonly found in nature. These Branchiobdellida worms live on the outside of crayfish and keep the gills of the crayfish clean by consuming any matter that has grown or lodged itself on the gill filaments. As such, the worms rely on the crayfish as a home and means of collecting food. Depending on food availability, this relationship can be mutually beneficial for both the crayfish and worm. Due to the worm's reliance of the crayfish and the mutually beneficial relationship they facilitate, the crayfish-branchiobdellidan relationship is known as a symbiosis. To best understand how microplastics affect the crayfish-branchiobdellidan symbiosis, we conducted experiments where we exposed crayfish with varying numbers of worms to a controlled dosage of microplastics for a prolonged period of time within artificial environments called mesocosms. Each microplastic dosage contained different types of microplastics, that mimicked the type and amount commonly found in nature. We found that crayfish with higher worm densities grew less when exposed to microplastics compared to those not exposed to microplastics. We also noticed that when microplastics were present, the worms exhibited more aggressive behavior, like consuming the gills of the crayfish. Based on assays which measured the number of resources accessible to the symbionts, our findings suggest that microplastics reduce the resource availability to the worms, which then triggers a change in their relationship with the crayfish host. Instead of being helpful, the worms start behaving more like parasites when exposed to microplastic. Ultimately, this study shows that microplastics can change the way different organisms interact, turning a beneficial symbiosis into a harmful one.

Freshwater streams in the developed world are becoming increasingly dominated by treated wastewater. Continually discharged into most surface waters, these effluents contain a suite of bioactive man-made chemicals, including steroid and non-steroid oestrogens, which have been found to feminise male fish, skew sex ratios, and cause reproductive failure. However, the consequences of reproductive disruption remain poorly explored at the population level. This thesis was initiated to evaluate how oestrogenic contaminants might influence the population ecology of a common cyprinid, the roach (Rutilus rutilus). An investigation encompassing population structure, multigenerational exposure and the role of additional drivers of fish population dynamics was undertaken to contextualise the effects of oestrogenic effluents on wild fish populations. Population genetic analysis of UK roach found they exhibit moderately high levels of genetic diversity and significant intra-river genetic structure. Genetically differentiated local subpopulations indicate little interbreeding and limited gene flow, consistent with a typical metapopulation that has not been homogenised by restocking. Similarly, my thesis demonstrates no significant relationship between effluent exposure and Ne (effective population size) or genetic diversity of roach populations, albeit a 65% reduction in Ne is possible at highly polluted sites. River stretches contaminated with high levels of effluent can support breeding populations, which recruit successfully with minimal immigration from less contaminated sites. Multigenerational effects of effluent exposure on roach were also evaluated experimentally using reproductive success from breeding adults over three generations. Lifelong exposure to 100% treated effluent resulted in feminised phenotypes (ovarian cavities and intersex condition) in males but no observable effect on females. Additionally, despite gonadal disruption in males and effluent exposure of their mothers, I found no detrimental effect on their ability to compete with control fish. Instead, reproductive success was primarily determined by body size. A novel approach considering additional fish population drivers suggests that genetic diversity and species diversity decline in parallel with an increasing presence of disturbed land, when combined with geographical isolation. In conclusion, group assemblage and genetic structure of fish populations appears multi-causal and cannot be disaggregated, such that a single environmental characteristic can be shown to drive patterns of population success.

Metals and radionuclides are environmentally relevant contaminants, yet their potential impacts on marine organisms have not been adequately evaluated. This is especially true for exposures of longer duration and/or lower contaminant concentration (i.e. chronic) which are often more representative of real world scenarios. In this context, a suite of biomarkers at different levels of biological organisation were investigated in an ecologically relevant bivalve species, Mytilus galloprovin- cialis after exposure to nickel (a metal), zinc pyrithione (an organometal) and tritiated water (a radionuclide). These contaminants were chosen based on their differing properties, and hence, mechanisms of action. All three contaminants produced genotoxicity (DNA strand breaks, as measured by the comet assay, and induction of micronuclei [MN]). For nickel (> 1800 µg L −1 ) and tritiated water (15 MBq L−1 ), biomarkers at lower levels of biological organisation (i.e. DNA strand breaks, MN, changes in the expression of key stress response genes) were more sensitive than those at higher levels (i.e. clearance rate, attachment, tolerance of anoxia). In particular, exposure to tritiated water for 14 days resulted in DNA damage and molecular alterations without affecting higher level responses. As environmental contaminants could interact with other physical or chemical stressors in a complex environment, further exploration of biological responses revealed modulation by hyperthermia with concomitant changes in the transcriptional ex- pression of key defence genes (hsp70, hsp90, mt20, p53 and rad51). In contrast to nickel and tritiated water, exposure to both 0.2 and 2.0 µM zinc pyrithione caused significant deviation from concurrent controls for every biomarker examined, suggesting that further investigation of the environmental impacts of this contaminant is particularly necessary. Variation in biological responses induced by different contaminants suggests that potential links between levels of organisa- tion should be evaluated on a contaminant-specific basis. The integrated, multiple biomarker approach used in the current study provides a robust methodology for such studies, which could be translated to other ecologically relevant species for proper evaluation of risks to both environmental and human health.

Manufactured nanomaterials (MNMs) from the rapidly increasing number of consumer products that contain MNMs are being discharged into waste streams. Increasing evidence suggests that several classes of MNMs may accumulate in sludge derived from wastewater treatment and ultimately in soil following land application as biosolids. Little research has been conducted to evaluate the impact of MNMs on terrestrial ecosystems, despite the fact that land application of biosolids from wastewater treatment will be a major pathway for the introduction of MNMs to the environment. To begin addressing this knowledge gap, we have conducted a series of experiments designed to test how bioavailable MNMs are to terrestrial ecoreceptors when exposed through a variety of pathways. First, we used the model organisms Nicotiana tabacum L. cv Xanthi (tobacco) and Triticum aestivum (wheat) to investigate plant uptake of 10, 30 and 50 nm diameter gold (Au) MNMs coated with either tannate (T-MNMs) or citrate (C-MNMs). Both C-MNMs and T-MNMs of each size treatment bioaccumulated in tobacco, but no bioaccumulation of MNMs was observed for any treatment in wheat. In a second exposure, we investigated the potential for bioaccumulation of MNMs from contaminated plant surfaces by a terrestrial secondary consumer, tobacco hornworm (Manduca sexta). We found that hornworms bioaccumulate Au MNMs, but that the assimilation efficiency of bioaccumulation was low. Hornworms eliminate ingested Au MNMs rapidly from 0-24 h, but very slowly from 1 d to 7 d. Finally, we used the model organisms tobacco and tobacco hornworm to investigate the potential for trophic transfer of Au MNMs. Biomagnification of Au MNMs was observed in the hornworms. We have demonstrated that MNMs of a wide range of size and with different surface chemistries are bioavailable to plants, that MNMs resuspended by wind, rain, biota, and mechanical disturbance from soil onto plant surfaces are bioavailable to terrestrial consumers, and that trophic transfer and biomagnification of plant accumulated MNMs can occur. These results have important implications for risks associated with nanotechnology, including the potential for human exposure.

PCBs are among the most problematic marine contaminants. Converging towards the oceans via the rivers and the atmosphere, they concentrate in sediments where they become a permanent threat to organisms living at their contact. PCBs are extremely resistant, bioaccumulated and some congeners are considered as highly toxic. The North Sea is considered as a highly contaminated area ; however little information is available regarding the impact of PCBs on key benthic organisms of this region. Ubiquist, abundant and generally recognized as a good bioindicator species, the common NE Atlantic sea star Asterias rubens (L.) is an ecosystem-structuring species in the North Sea and was chosen as an experimental model. The present study focused on the characterization of PCB bioaccumulation in A. rubens exposed through different routes (seawater, food, sediments) and on subsequent biological responses, at immune and sucellular levels. The considered responses were respectively (i) the production of reactive oxyggen species (ROS) by sea stars amoebocytes, which constitutes the main line of defence of echinoderms against pathogenic challenges and (ii) the induction of a cytochrome P450 immunopositive protein (CYP1A IPP) which, in vertebrates, is involved in PCB detoxification. Experimental exposures carried out have shown that A. rubens efficiently accumulates PCBs. Exposure concentrations were always adjusted to match those encountered in the field. PCB concentrations reached in sea stars during the experiments matched the values reported in field studies ; therefore our experimental protocol was found to accurately simulate actual field situations. Uptake kinetics were related to the planar conformation of the considered congeners : non-coplanar PCB uptake was described using saturation models, whereas coplanar PCBs (c-PCBs) were bioaccumulated according to bell-shaped kinetics. Non-coplanar congeners generally reached saturation concentrations whithin a few days or a few weeks, which means that sea stars can be used to pinpoint PCB contamination shortly after occurrence. On the other hand, c-PCB concentrations reached a peak followed by a sudden drop, indicating the probable occurrence of c-PCB-targeted metabolization processes in sea stars. Our experimental studies also demonstrated that seawater was by far the most efficient route for PCB uptake in sea stars and that even if PCB levels in seawater are extremely low compared to sediment-associated concentrations, seawater constitutes a non-negligible route for PCB uptake in marine invertebrates. Among the different body compartments, bodywall displayed the highest bioaccumulative potency and can therefore be considered as particularly interesting for field biomonitoring applications. Rectal caeca, which play a central role in digestion and excretion processes in sea stars, have also rised particular interest as results suggest these organs could be involved in the elimination of PCB 77 degradation products. The field work carried out during the present study showed that PCB concentrations measured in A. rubens tissues reflect environmental levels of certain congeners. As it was the case in experimental conditions, A. rubens differentially accumulated PCB congeners according to their planarity. Strong relationships were found between concentrations measured in sediments and those determined in sea stars body wall for certain non-coplanar congeners (e.g. 118 and 138), thus allowing to consider A. rubens as a suitable bioindicator species for medium-chlorinated PCB congeners. On the other hand, sea stars appeared to be able to regulate -to a certain extent- their content in coplanar PCBs. This implies that (i) A. rubens cannot be strictly considered as an indicator organism for c-PCBs and (ii) c-PCBs probably affect essential aspects of sea star biology, potentially leading to deleterious effects. The present study addressed effects of PCB exposure on A. rubens biology, in both experimental and field conditions. In experimental conditions, PCBs were found to significantly alter ROS production by sea stars amoebocytes. This alteration also occurred in a congener-specific way : c-PCBs were found to significantly affect, and probably impair sea stars immune system, whereas non-coplanar congeners had no effect. In the field, the PCB contribution to immunotoxicity could not be determined because none of our studies considered ROS production along with c-PCB concentration measurements. However, the levels of ROS production by sea stars amoebocytes measured in field and experimental conditions were found to potentially lead to altered immunity, and therefore to impair sea stars defence against pathogenic agents. A specially designed ELISA was used to measure CYP1A IPP in experimental and field conditions. Experimental work has shown that the induction of this protein was related to PCB exposure in a congener-specific fashion : c-PCBs alone were found to strongly induce the production of CYP1A IPP according to a dose-dependent relationship. These results have highlighted many similarities between the dioxin-like responsiveness of CYP1A IPP induction in sea stars and that occurring in vertebrates. This strongly suggests similarities in the toxicity-triggering mechanism of dioxins and c-PCBs. In the field, CYP1A IPP induction was found to be significantly related to PCB levels determined in bottom sediments. It can thus be considered as a valuable biomarker. Further research is however needed to better characterize the influence of physico-chemical and physiological parameters on CYP1A induction to refine the interpretation of the information gathered via this biomarker. Results obtained in our study have lead to questionning international regulations applying to PCB biomonitoring in the marine environment. For instance, we strongly suggest that the selection of congeners to be systematically considered should be revised to include c-PCBs. Indeed, in our experiments PCB toxicity was almost always attributable to the sole c-congeners. Historically, determination of c-PCB concentrations was extremely difficult due to analytical limitations ; however, nowadays, these problems have been overcome and do no more justify their exclusion from monitoring studies. Although A. rubens appeared to be quite resistant to PCB contamination, levels measured in sea stars from the southern North Sea can possibly affect their immune and endocrine systems in a subtle way, but with relatively low risk for this species at the short-term. However, this does not mean that other species in this region undergo similarly low risks, or that sea star-structured ecosystems may not become affected in the long-term

Spilled heavy fuel oil (HFO) sinks within the water column and accumulates in sediments, affecting aquatic organisms that are not typically exposed to oils that float. Previously, the 3-4 ring alkyl substituted polycyclic aromatic hydrocarbons (PAHs) have been identified as the major toxic components in crude oil. Since HFO is comprised of higher concentrations of 3-4 ringed alkyl PAH and an abundance of 5-6 ringed PAH relative to crude oil, it is predicted to be more toxic to the early life stages of fish. An effects-driven chemical fractionation (EDCF) of HFO 7102 was undertaken to establish the toxicity relative to crude oil, and to identify the compounds that are bioavailable and chronically toxic to the early life stages of fish. In this EDCF, the complex HFO 7102 mixture was separated by low temperature vacuum distillation into three distinct fractions, 2, 3 and 4. Each fraction was assessed using a chronic bioassay to determine whether it contained components that caused toxicity to rainbow trout embryos similar to that of the whole oil. Acute bioassays with juvenile trout demonstrated the presence of compounds that induce cytochrome P450 enzymes, an indicator of exposure to PAH. Fraction 3, the fraction more toxic than the parent mixture, was further separated by cold acetone extraction into fraction 3-1 (PAH-rich extract) and fraction 3-2 (wax residue), and assessed with the same bioassays. Simultaneous chemical analysis with bioassays guided the fractionation, and identified compounds abundant and consistently present in toxic fractions. Due to resistance to dispersion of HFO, a chemical dispersant was used with vigorous mixing to drive the maximum amount of oil into solution to minimize the potential for false negatives and the volume of test material used. The potency of HFO 7102 and its fractions were also measured using water accommodated fractions (WAFs) produced by a continuous flow system of water flowing through oil coated gravel. Both exposure methods traced the toxicity from whole oil into fractions containing higher concentrations of 3-4 ring alkyl PAH, similar to crude oil. This research is the first toxicological assessment of HFO 7102, which is essential for determining the risk of spills of HFO to fish, and whether the risk of oils can be predicted from their alkyl PAH composition. / Thesis (Master, Biology) -- Queen's University, 2013-01-24 14:14:16.278