A novel macroinvertebrate biomonitor for metals in the freshwater environment

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Date
2022-08-24
Authors
O'Callaghan, Irene
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University College Cork
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Abstract
Clean water is vital to human and ecological health. Freshwaters are relied upon for drinking water abstraction and sanitation, and they are the foundation of many ecosystems. Nonetheless, freshwaters are threatened across the globe by increasing quantities and varieties of emerging contaminants. Our ability to identify and respond to freshwater contamination is limited by our comprehension of fundamental aquatic mechanisms, and the cost and sensitivity of quantitative analytical techniques. This thesis aims to address these issues, through the investigation of bioaccumulative amplification of environmental metal concentrations using benthic macroinvertebrates. Bioaccumulative amplification is an approach employing the natural bioaccumulation of environmental contaminants by benthic macroinvertebrates as an in-situ preparation step in the analytical process, thus relaxing the effective limits of detection. Field evaluation of the technique shows substantial improvement in method sensitivity over the direct quantification of contaminants in the water phase. Lab-based evaluation demonstrates the applicability of this technique to both bulk and nano-scale contaminants, and in both ex-situ and in-situ environments. A fundamental relationship between elemental thiophilicity and bioaccumulative potential is described herein, and is evaluated in both fieldinvestigation and meta-analysis of existing datasets. This relationship holds across varying taxa and environmental conditions, and in both marine and freshwater systems. The finding supports the hypothesis that metallothionein is responsible for the biological homeostasis of physiological metals and aids in the protection against metal toxicity. The thiophilic scale is thus presented as a tool for predicting the bioaccumulative potential and ecological risk of a given contaminant. To date, the process of bioaccumulation has been modelled as an input-only process. Ecdysis, or moulting, is presented as a process that leads to periodic removal of accumulated contaminants. This process is shown to have a significant impact on measured bioaccumulated concentrations. A resulting error is introduced into bioaccumulation studies that overlook this process; steps to minimise this error are also discussed.
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Bioaccumulation , Macroinvertebrate , Freshwater , Metal , Biomonitoring
Citation
O'Callaghan, I. 2022. A novel macroinvertebrate biomonitor for metals in the freshwater environment. PhD Thesis, University College Cork.