1,721,031 research outputs found
The use of non-targeted proteomics and in vitro bioassays as a non-destructive approach towards the development of biomarkers of contaminant exposure in threatened marine wildlife
No full textBiomarkers of chemical exposure and effect are an important tool for monitoring the
health of threatened species that are vulnerable to the adverse effects of prolonged
contaminant exposure. However, there are many challenges that have limited the
discovery of new biomarkers of chemical exposure in protected species, particularly the
constraint on the use of destructive methods such as in vivo experimentation. This thesis
first examines the current methods of biomarker discovery as reported in the literature
to identify what methods future research in this field should focus on. A systematic
quantitative review of methods of non-destructive biomarker discovery in wildlife
highlighted the hinderance of these limitations on current research as well as the paucity
of studies harnessing in vitro techniques (Chapter 2). The use of in vitro bioassays is not
uncommon in ecotoxicology, however, these assays are largely targeted at one or
several known markers. Non-targeted proteomics analyses allow for the discovery of
new biomarkers, which is important considering wildlife may continually be exposed to
new compounds and mixtures. Therefore the application of in vitro and in vivo nontargeted
proteomic analysis as a tool for biomarker discovery was examined. To do so,
sea turtles were used as a model species due to their priority conservation status and
their susceptibility to the adverse effects of contaminant exposure. Cell lines derived
from sea turtles exposed in vitro to environmentally relevant contaminants were used as
a model for the in vitro analyses. Firstly, experimental sources of variation on protein
expression (time, concentration and contaminant type) were explored (Chapter 3)
revealing a strong effect of exposure time on observed proteomic changes and little
effect from concentration. Furthermore, potential candidate biomarkers were discovered
and the relevance of this method to in vivo molecular responses was demonstrated with
the observation of known in vivo markers of exposure dysregulated in response to
chemical exposure. Then, the influence of biological sources of variation (tissue type) were examined with cells derived from several tissue types exposed in vitro to
contaminants (Chapter 4). Different tissue types showed a different response to
contaminant exposure and known in vivo biomarkers of exposure were again observed.
Furthermore, potential new biomarker candidates were identified that would be
beneficial for future research in this field to explore. Finally, non-targeted proteome
profiling was applied to biological samples of wild-caught animals to examine its
potential in biomarker discovery (Chapter 5). The proteome of the blood plasma of three
Southeast Queensland sea turtle populations exposed to different chemical profiles were
compared, and distinct differences in population protein expression were observed.
These differences indicated altered immune states between populations, which could be
caused by contaminant and/or pathogen exposure. In conclusion, this novel method of
non-targeted proteomic analysis of both in vitro and in vivo samples provides a wealth
of information about how contaminants affect sea turtles at the cellular and whole
organism level and is a promising avenue to enhance wildlife toxicology. However, it
was discovered that it is challenging to draw correlations between in vivo and in vitro
global protein expression, and furthermore that sources of experimental variation can
greatly influence the outcomes. Therefore, it is vital that future studies on this area focus
on reproducibility of these sensitive methods before fully utilising them for directing
wildlife toxicology research.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Environment and ScScience, Environment, Engineering and TechnologyFull Tex
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Assessing the impact of chemical exposure on the health of endangered sea turtles through toxicokinetics and toxicodynamics
No full textThe green sea turtle, Chelonia mydas, spends a considerable part of its life in coastal waters foraging on seagrass and/or algae, which brings it close to anthropogenic pollutant sources. Elevated concentrations of chemical contaminants from urban, industrial and agricultural run-off accumulate in coastal environments. These pollutants have the potential to cause serious harm to C. mydas populations. However, exposure and toxicity data are challenging to obtain for free-ranging, protected wildlife species like C. mydas. Furthermore, a lack of quantitative tools linking long-term external contaminant exposure, the uptake and tissue distribution of chemicals (toxicokinetics), and the biological pathway perturbations related to adverse health outcomes (toxicodynamics) hamper efforts by scientists and policymakers to quantify the risk of pollutants adversely affecting C. mydas
health. Changes in C. mydas population abundance, in turn, may affect the marine seagrass ecosystems, which, by extension, could potentially also impact human health and animals that rely on seagrass habitats.
The present thesis provided the means to research the hypothesis that land-based contaminants adversely impact the health of Australia’s resident green turtle populations. The following chapters in this thesis investigate the validity of this hypothesis. Valuable experimental toxicokinetic and toxicodynamic data are collected and described in Chapters 2 and 3. Chapter 4 used data from Chapter 3 to develop tools to confirm the initial hypothesis. Overall, this thesis describes the development of tools to aid risk assessors and policymakers in setting safe chemical exposure levels for green sea populations.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Environment and ScScience, Environment, Engineering and TechnologyFull Tex
Shell walls: A new hope. Using barnacle shell isotopes as a conservation tool for understanding the movement ecology of threatened sea turtles
No full textUnderstanding the geographic distribution of sea turtles within their sub-populations could enhance conservation and management, especially for sub-populations that are the most threatened. Isotope techniques have been used for this purpose and have become popular in the past decade, with an increasing year-to-year trend in published studies. Via systematic literature review of all studies using isotopes to understand sea turtle ecology, this thesis first presents a robust understanding of the current state of the science, identifying knowledge gaps and priorities for future sea turtle conservation research (Chapter 2). This identified that very few stable isotope studies aimed at understanding foraging distributions have been completed on threatened sub-populations of sea turtles, whereas those considered of least concern by the IUCN have been the focus of many. I aimed to address this mismatch between stable isotope studies and conservation needs by developing, validating, and applying a novel isotope technique to understand the foraging distribution of critically endangered South Pacific loggerhead turtles (Caretta caretta), and in doing so identifying critical habitats for priority management. The technique presented uses isotope ratios from commensal barnacle shells, which vary with temperature (SST) and salinity (SSS) rather than turtle diet. Barnacle shells are formed sequentially, storing chemical information about of the surrounding conditions at the time of formation. This makes it possible to assign a date to samples, and compare isotope ratios with the spatial and temporal distribution of sea water parameters (SST and SSS), if the growth of the animal is well understood. Thus, in this thesis I tested the applicability of using barnacles to understand sea turtle foraging distribution by quantifying barnacle growth rates (Chapter 3), regional relationships between barnacle isotopes (C and O) and SST & SSS (Chapter 5), and discriminating between foraging areas based on time dependent isoscapes for barnacle shell (Chapter 4, 5). Finally, the technique is applied to predict the home area of loggerhead turtles that nest in southern Queensland, Australia, identifying hotspots and relationships between nesting and foraging habitats (Chapter 6). This thesis demonstrates that isotopes from barnacle shells can be used to identify the origin and migration distances of host turtles at varying spatial scales, depending on water chemistry gradients present at the time and location of shell formation. In eastern Australia is it possible to assign turtles to home areas with >86% accuracy when areas are separated by at least 400 km (Chapter 4). Globally, many coastal areas are likely to offer similar or better resolution to this, while pelagic waters will typically offer lower resolution. This thesis also shows that estuarine habitats are important foraging habitats for adult loggerhead turtles, probably more so for southern foragers, while marine habitats are clearly important in northern Australia. Future research should focus on developing isoscapes for barnacle shell in other regions, and combining barnacle analyses with other methods to improve the achievable resolution. I also expect that this technique can be applied widely to other taxa and objects that carry commensal barnacles throughout marine journeys.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Environment and ScScience, Environment, Engineering and TechnologyFull Tex
Development, validation and application of an in vitro toxicological model for sea turtles
No full textChemical contaminants accumulate in marine megafauna globally, including sea turtles. Logistical and ethical constraints around exposure experiments using large, long-lived, and often threatened species, has limited our understanding of how these pollutants may affect wildlife. The knowledge gaps are outlined in a systematic quantitative literature review (Chapter 2), which found that in vitro bioassays offer an ethical, reproducible, and cost-effective alternative for investigating the effects of contaminants. The development of an in vitro toxicological model can provide important information for conservation and management. This thesis aimed to develop, validate and demonstrate the applicability of an in vitro model for sea turtles. Cell cultures were established from skin and internal organs of green sea turtles including heart, small intestine, ovary and liver. Important questions concerning individual variation (Chapter 3) and variation between tissue types (Chapter 4) were addressed to select an ideal cell culture for further testing and validation. Variation in cytotoxic response was generally low between cell cultures established from different individuals. This suggests that one cell line can be used representatively. However the results highlight the importance of preliminary analysis in order to select a cell culture with an average response and this chapter provides a framework for doing so. Variation in cytotoxic response between tissue types was also generally low, though a clear pattern in organ sensitivity was apparent. This pattern identified skin as the most sensitive tissue type. This is particularly useful for future research, as skin can more readily be obtained from live, healthy turtles. Based on the results from Chapter 3 and 4, an ideal cell culture was selected for continued use. The usefulness of the selected cell culture was validated in two additional bioassays measuring oxidative stress and genotoxicity to test the effects of 16 model compounds (Chapter 5). Oxidative stress was measured through the formation of reactive oxygen species and genotoxicity was measured through the formation of a micronucleus. The results from cytotoxicity (Chapter 4), oxidative stress and genotoxicity assays (Chapter 5) were used in a screening risk assessment for wild turtle populations based on contaminant accumulation data from the literature. These screening risk assessments identified a number of locations where turtles may be at risk from current contaminant concentrations. Finally, the applicability of the in vitro model to broader ecological questions was demonstrated (Chapter 6). Blood extracts of turtles from three different foraging grounds were used in the bioassays to examine differences in exposure. This data, along with chemical analysis of trace elements, was used to assess risk from chemical exposure to these populations. Blood extracts from Moreton Bay turtles caused significantly stronger responses in both the cytotoxicity assay and oxidative stress assay, both of which were important factors contributing to differences between foraging grounds when combined with trace element data. The measured effect concentrations for blood extracts from Moreton Bay turtles were approximately half the concentration found in blood, indicating a higher risk associated with chemicals in blood from turtles in Moreton Bay compared to the other sites monitored. These results illustrate that using in vitro bioassay data can provide unique information into exposure and effects in sea turtles, and this data can be used to identify and prioritise populations at risk. This thesis has demonstrated that species-specific in vitro methods are suitable and useful in identifying chemical risk to sea turtles. In vitro methods can be used to understand the molecular initiating events of chemicals in sea turtles, data from these studies can be used in screening risk assessments, and finally, in vitro models can be used with biological samples to assess current concentrations and mixtures of contaminants. Altogether, species-specific in vitro models offer a promising avenue for sea turtles and other marine megafauna as well.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Environment and ScScience, Environment, Engineering and TechnologyFull Tex
The combined and interactive effects of multiple stressors on Great Barrier Reef ecosystems
No full textCoastal ecosystems are under threat by an increasing number of natural and anthropogenic stressors. These stressors co-occur in countless combinations, raising questions in the scientific community about their combined and/or interactive effects on individuals, populations and ecosystems. Environmental management of multiple stressors is challenging, as the governance of stressors are still largely based on individual effects, despite growing evidence of interactive effects in coastal ecosystems. As a result, the field of multiple stressor research is rapidly expanding to better understand, predict and manage stressor interactions.
This thesis aims to address questions surrounding deteriorating water quality, as an indication of ecosystem health, of the Great Barrier Reef (GBR). Land-based runoff has been identified as the greatest contributor to poor water quality in inshore marine ecosystems, such as the GBR. The three main water quality pollutants common to the GBR include pesticides, excess nutrients and suspended sediments. These pollutants originate from coastal development and agricultural practices and are transported to receiving waters via flood plumes. Following high rainfall during the Queensland wet season, GBR ecosystems are simultaneously exposed to high concentrations of pesticides, nutrients and sediments. This thesis presents a collection of related chapters that assess the effects of these three water quality stressors on coastal ecosystems.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Environment and ScScience, Environment, Engineering and TechnologyFull Tex
Reproductive Toxicology of Sea Turtles
No full textMany sea turtle species are threatened or endangered because of human activities including habitat loss, bycatch, and pollution. Various studies from around the world have found that anthropogenic contaminants accumulate within sea turtle tissues. Sea turtles have high site fidelity to coastal habitats, which are often close to human development, and therefore, pollutant sources. However, limited research has been performed on the impacts of contaminants on sea turtle reproduction. These research gaps were addressed by conducting a quantitative literature review of reptile reproductive toxicology to inform sea turtle reproductive toxicology research (Chapter 2). Three research priorities for better understanding reproductive toxicology in sea turtles were identified. These included: assessing contaminant exposure and maternal transfer in nesting sea turtles of known foraging locations (Chapter 3), investigating impairment of sex hormone production and the prevalence of common endocrine disruptors in sea turtles at various foraging locations (Chapter 4), and exploring the potential for contaminants to influence the sex determination of sea turtle hatchlings (Chapter 5).
A chemical risk assessment of two loggerhead sea turtle (Caretta caretta) nesting beaches in eastern Australia revealed a direct link between nesting turtle foraging location and hatchling contaminant concentrations (Chapter 3). There were significant differences in contaminant exposure and maternal transfer between two nesting locations, and these differences were directly correlated with known turtle foraging locations. Particularly, nesting turtle foraging locations reflected many of the contaminant differences found. There were also correlations between maternal blood and egg contaminant concentrations for a number of trace elements. In addition, cytotoxicity in a sea turtle specific cell-based bioassay suggested that organic contaminant concentrations in the blood of turtles foraging in some locations may be high enough to cause cell damage in vitro. Overall, however, the risk of trace elements and organic contaminant exposure to hatchling health were considered low at both nesting beaches. Despite this, these data suggest that reducing contaminant exposure in foraging locations could translate to reductions in trace element concentrations in hatchling turtles.
Within the five green turtle foraging grounds investigated in Chapter 4, there was evidence of widespread exposure to ethinylestradiol (EE2) and nonylphenol (NP) in immature green turtles. EE2 and NP are known endocrine disruptors, and well-studied for their negative estrogenic effects on aquatic organisms. EE2 and NP have been found to alter sex determination and alter sex hormone production in reptiles including freshwater turtles. EE2 residues in immature green turtles were up to 10 times higher than persons taking EE2 medication. There is little research as to whether EE2 and NP can maternally transfer to offspring. Maternal transfer of these compounds may lead to feminization of offspring. This study demonstrated that EE2 and NP exposure was common across many foraging locations in Queensland, and that the effects of these compounds on reproductive endpoints need to be investigated further.
In Chapter 5, sixteen green turtle clutches that were part of a parallel study on the impacts of nest cooling on sex ratios were examined for their trace element and organic contaminant concentrations. The contaminants found were converted into three indices: the percent of hatchlings in a clutch with trace element concentrations over median (TEOM), the percent of hatchlings in a clutch with estrogenic trace element concentrations over median (EstroEOM), and a predicted 17β-estradiol equivalent activity (PEEQA) of estrogenic trace elements. Many of the clutches deviated from their predicted sex ratio based on temperature (hereby sex ratio deviation), with some clutches having 90% more females than expected. When excluding an outlier, sex ratio deviation had a significant positive relationship with cadmium, antimony, and EstroEOM. In addition, there were significant relationships between mean clutch concentrations of cobalt, lead, antimony, barium, PEEQA, TEOM, EstroEOM and sex ratio. While there were no specific contaminants found to definitively affect sex determination, overall contaminant trends suggested that contaminants may affect sea turtle hatchling sex determination.
This thesis contributes to the priorities of sea turtle reproductive toxicology research that were established in the literature review (Chapter 2). Overall, I found that that sea turtle foraging grounds can influence hatchling contaminant accumulation in nesting populations; immature turtles are exposed to endocrine disrupting compounds within their foraging grounds; and that the potential effects of contaminants on sea turtle hatchling sex determination should be the subject of future studies. These research outcomes support management and conservation of sea turtles, illustrating that reducing contaminant inputs at sea turtle foraging locations can help reduce the potential reproductive harm of anthropogenic activities, and therefore may reduce the risk hatchling feminization from contaminants.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Environment and ScScience, Environment, Engineering and TechnologyFull Tex
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