1,721,011 research outputs found
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
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
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
