Browsing by Author "Keough, MJ"

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    Experimental design and statistical analysis in aquatic live animal radiotracing studies: a systematic review
    (Taylor & Francis, 2021-03-18) McDonald, S; Cresswell, T; Hassell, K; Keough, MJ
    Live animal gamma radioisotope tracing enables the monitoring of real-time contaminant uptake and retention in individual animals. It has been employed by ecotoxicologists to understand how animals respond to a variety of aquatic stressors. The use of the technique increases the complexity of the experimental design, resulting in the production of highly detailed and robust longitudinal data of individual animals. The greater complexity of the statistical models that underpin this data create risks from data being treated incorrectly. A systematic review of the literature was undertaken to comprehensively evaluate the experimental design and statistical approaches employed by current aquatic live animal radiotracing studies. The experimental design of current studies was categorized into one of five design “families”. Each experimental design could be described by at least one statistical model, which in turn informs a specific statistical approach. Collectively, 7% of studies provided insufficient information to determine the experimental design used, and 24% of studies undertook no formal statistical analysis of results. When the statistical approaches used in current studies were examined, in most cases the correct approach was undertaken, with only 18% of studies using a statistical approach that did not match the chosen experimental design. This review provides clear guidance on the analysis and interpretation of data collected from each experimental design and explains the advantages and disadvantages of each. Additionally, this paper identifies four key suggestions for future researchers, and provides commentary on the ethical, logistical and cost considerations associated with undertaking experiments that use live animal radiotracing. © 2021 Taylor & Francis Group.
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    Metal forms and dynamics in urban stormwater runoff: new insights from diffusive gradients in thin-films (DGT) measurements
    (Elsevier, 2022-02-01) McDonald, S; Holland, A; Simpson, SL; Gadd, JB; Bennett, WW; Walker, GW; Keough, MJ; Cresswell, T; Hassell, KL
    Stormwater runoff typically contains significant quantities of metal contaminants that enter urban waterways over short durations and represent a potential risk to water quality. The origin of metals within the catchment and processes that occur over the storm can control the partitioning of metals between a range of different forms. Understanding the fraction of metals present in a form that is potentially bioavailable to aquatic organisms is useful for environmental risk assessment. To help provide this information, the forms and dynamics of metal contaminants in an urban system were assessed across a storm. Temporal patterns in the concentration of metals in dissolved and particulate (total suspended solids; TSS) forms were assessed from water samples, and diffusive gradients in thin-films (DGTs) were deployed to measure the DGT-labile time-integrated metal concentration. Results indicate that the concentrations of dissolved and TSS-associated metals increased during the storm, with the metals Al, Cd, Co, Cu, Pb and Zn representing the greatest concern relative to water quality guideline values (GVs). The portion of labile metal as measured by DGT devices indicated that during the storm a substantial fraction (∼98%) of metals were complexed and pose a lower risk of acute toxicity to aquatic organisms. Comparison of DGT results to GVs indicate that current GVs are likely quite conservative when assessing stormwater pollution risks with regards to metal contaminants. This study provides valuable insight into the forms and dynamics of metals in an urban system receiving stormwater inputs and assists with the development of improved approaches for the assessment of short-term, intermittent discharge events. © 2021 Elsevier Ltd.