1,721,027 research outputs found
Extreme changes in salinity drive population dynamics of Catostylus mosaicus medusae in a modified estuary
No full textModifications to estuaries through the construction of barrages alter the natural dynamics of inhabitant species by controlling freshwater inputs into those systems. To understand the effects of modified freshwater flows on a native scyphozoan jellyfish, Catostylus mosaicus, and to identify the environmental drivers of medusa occurrence, we analysed a 20-year observational dataset composed of 11 environmental variables and medusa presence/absence from 15 sampling stations located below the Fitzroy Barrage, in the Fitzroy River, Queensland. Major decreases in salinity (minimum salinity 0) occurred approximately 16 times during the 20-year period and medusae disappeared from the estuary following every major freshwater flow event. Salinity was identified as the most influential variable contributing to variation in the number of upper estuary sites reporting jellyfish. We then ran two laboratory experiments to test the following hypotheses: (i) prolonged decreases in salinity impair survival, pulsation, and respiration rates of C. mosaicus medusae; and (ii) transient decreases temporarily impair pulsation and respiration but medusae recover when salinity returns to normal levels. Medusae were unable to survive extended periods at extreme low salinities, such that they would experience when a barrage opens fully, but had significantly higher survival and recovery rates following smaller, transient changes to salinity that might occur following a moderate rainfall event. This demonstrates for the first time that modification of freshwater flow by a barrage regulates the population dynamics of an estuarine jellyfish, and highlights the need for robust, long term datasets, and to firmly embed experimental approaches in realistic ecological contexts
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Management of Recycled Water Quality in the Urban Environment
No full textA rapid expansion in use of recycled water in urban Australia has occurred over the last decade, prompted mainly by a reduction in water supplies due to drought, increasing awareness of the impact of climate change on water resources and changes in government water recycling policies. This expansion has resulted in a 117% increase Australia wide in the reuse of effluent from wastewater treatment plants by major water authorities. This study describes the developments in recycled water quality, from 1999 to 2009, during its progress from ‘treated effluent’, to ‘reclaimed water’, to ‘recycled water’ and then to ‘purified recycled water’. The developments studied include changes in people’s concerns about recycled water quality, changes in the benchmarks of water quality, as described in water recycling guidelines and effluent discharge licences, and changes in recycled water quality during storage in open ponds. This study also describes preliminary investigations into a novel approach, of applying a microbial source tracking technique, to follow changes in water quality during conventional wastewater treatment processes and storage in open ponds.
Concerns about recycled water quality were examined by distributing a questionnaire in mid-2000 to providers and users of recycled water in Queensland. Four out of five respondents had concerns about aspects of recycled water quality including microbiological components (viruses, parasites and bacteria), salinity related components, aggregate components (pH and solids), nutrients and organic components (pesticides and endocrine disruptors). One in four respondents expressed concern about quality variability, particularly those from low population density areas. One in five users had observed quality changes during distribution to the point-of-use including nutrients, chlorine, suspended solids, colour and odour. Half of the providers and one in five users in 2000 proposed to expand their usage of recycled water in the near future and one third of the non-user respondents proposed to commence using recycled water in the following 5 years.
Guidelines for the use of recycled water were reviewed in 2003 and, at that time, the national, State and Territory guidelines contained similar recommendations, for hazard identification and risk assessment, using controls implemented through treatment and management practices. However, despite the framework provided by the national
guidelines, the State and Territory guidelines differed from them concerning sources of recycled water, reuse options, nominated quality criteria, monitoring frequencies, sampling and testing methods and accreditation. Legislation for effluent from wastewater treatment plants discharged to the environment varied between States and Territories and, in most cases, the licences were site specific. The general differences in discharge licences and reuse guidelines included the location of monitoring sites, nominated water quality criteria and compliance levels.
At the completion of this review, the authors proposed that establishment of recycled water schemes could be enhanced by standardisation of the water quality monitoring requirements for effluent discharge, particularly for indicator organisms, with those for effluent reuse through collaboration between licensing and guideline authorities. It was also proposed that a single point of contact for recycling scheme approval be established, in each State or Territory, and that the national guidelines for reclaimed water be better integrated with those for fresh and marine water. Developments in the years since the survey and review were undertaken have been summarised, including the usage, acceptance and quality of recycled water and the latest changes in recycled water guidelines.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of EnvironmentScience, Environment, Engineering and TechnologyFull Tex
Assessing Structural Complexity of Mangroves and its Implications for Ecosystem Services
No full textAs dominant ecosystems on protected tropical and subtropical shorelines, mangroves are globally important for essential ecosystem services such as acting as nursery habitat for juvenile nekton, land building and coastal protection. The structural complexity associated with the aerial roots of mangroves strongly underpins these services. However, due to the lack of a satisfactory method for measuring and quantifying this complexity, the relationship between complexity and mangrove ecosystem services is still obscure. The objectives of this study were (1) to find a low-cost method for realistically quantifying habitat complexity; and (2) to assess the importance of habitat structural complexity to the principal ecosystem services offered by mangroves, namely, supporting fish assemblage, flow attenuation and sediment trapping. An innovative, simple, and low-cost method based on an RGB_D scanning sensor (Kinect) and free and readily accessible software (Meshlab, Matlab, Qubicle Constructor and Voxeliser) was used to capture realistic 3D models of mangrove aerial roots. This low-cost approach provides a novel method to capture and measure structural complexity at a mesoscale in a full 3D approach, enabling an analysis of the relationship between habitat complexity and mangrove ecosystem services. The fractal dimension (FD) and AVR (area/volume ratio of the 3D model) indices were developed to quantify mangrove root structural complexity. The cube counting method was used for three-dimensional characterisation of FD of the space around aerial roots. To assess the apparent complexity of the structure to fish potentially using the roots, rectangular prisms with dimensions corresponding to the allometry of the fish were used to estimate the FD values.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Griffith School of EnvironmentScience, Environment, Engineering and TechnologyFull Tex
Ecosystem Engineering by Euastacus sulcatus (Decapoda: Parastacidae) in the Hinterland of the Gold Coast, Queensland, Australia
No full textIn the mountains of the Gold Coast Hinterland (Queensland, Australia), Euastacus sulcatus (Decapoda: Parastacidae) is the largest aquatic invertebrate, largest member of the aquatic shredder guild, and probably plays a key role in the area’s stream ecology. The objective of this study was to investigate the ecological effects of E. sulcatus in the streams of the Gold Coast Hinterland, but in particular to assess the species’ capacity to act as an effective ecosystem engineer, obtain measures of the ecosystem services provided by the species, and evaluate the likely impacts of the crayfish on downstream water quality. To achieve this objective, an estimate of the population size of E. sulcatus was obtained; a series of experiments measured the species’ capacity to liberate nutrients from leaf litter, reduce the particle-size of the leaf litter, and mobilise and redistribute organic and inorganic materials in a flowing stream environment. This information allowed estimation of the species’ ecological impact(s) per unit time as a measure of the ecosystem services provided by E. sulcatus in the headwater streams of the study area. During this study E. sulcatus was common and abundant with a within-stream density of ~0.5 crayfish m-2. The total population of E. sulcatus in the study area was estimated at >860,000 crayfish. Correction for strong seasonal variation in activity was required for ecological impact calculations, and the “ecologically effective” population was estimated at >570,000 crayfish (biomass ~12 tonnes wet weight (WWT)). Crayfish significantly liberated nitrogen and phosphorus from leaf litter into the water column via consuming leaf litter and excreting nutrients. The phosphorus dynamic was complex, however the overall effect of crayfish was to facilitate eventual “loss” of phosphorus from the system with binding/absorption to substrates, particularly leaf litter, evident as the mechanism. The ecologically effective population was estimated to liberate at least 140 kg of nitrogen, 1.5 kg of phosphorus, and facilitate the loss of around 0.15 kg of soluble phosphorus from leaf litter per annum. Crayfish consumed large amounts of leaf litter while significantly reducing its particle-size. The ecologically effective population consumed at least 14 tonnes WWT of whole leaf litter, producing ~4.5 tonnes WWT of fine particles (<1 mm), with a nett consumption of ~9 tonnes WWT leaf litter per annum. The day-to-day activities of crayfish led to significant mobilisation and downstream export of materials 1 mm diameter, with about half this material of organic origin. The ecologically effective population facilitated the mobilisation and downstream export of around 90 tonne-meters (dry weight) material per annum. Given this annual crayfish-export effect is dramatically overwhelmed by the periodic flood spates in the area, it is unlikely crayfish-mediated export of materials is negative for downstream water quality. In the field it is anticipated that the liberated nutrients will be stripped from the water column by other biota, and/or abiotic processes, and eventually recycled back into and retained in the headwater ecosystems. Similarly, crayfish-mediated particle-size reduction of leaf litter will facilitate further processing by other biota, and recycling and retention of this material in the headwater regions. In the typical baseflow conditions, the instream mobilisation of materials will be positive for maintaining the high quality of water flowing from the headwater streams, by maintaining streambed complexity and ecological processes such as enhanced decomposition of organic detritus. Euastacus sulcatus is a common, abundant and ecologically aggressive species, and the results of this study support a conclusion that this species is an effective ecosystem engineer. The population of E. sulcatus clearly provides a number of ecosystem services, and even lower bound estimates indicate the magnitude of these services are fairly substantial at a local scale, and must be of appreciable benefit in maintaining the function and health of the headwater stream ecosystems.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Griffith School of EnvironmentScience, Environment, Engineering and TechnologyFull Tex
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