Estimation of demographic toxicity through the double bootstrap |
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Authors: | Grist Eric P M Crane Mark Jones Claire Whitehouse Paul |
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Affiliation: | School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK. |
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Abstract: | Toxicity to organisms is usually expressed in terms of an observable effect on individuals from which a summary endpoint (such as the NOEC or ECx) is derived for risk assessment and environmental quality standards. However, toxicity evaluated in terms of a demographic endpoint may be more relevant to such regulatory applications. In this paper the effect of toxicity on population growth rate r is explored in tandem with a 'double bootstrap' to incorporate uncertainty. Exemplifying the approach with a set of individualized life table response data obtained for Daphnia magna exposed to zinc sulphate solution, the influence of increasing concentrations is assessed. A demographic-based metric for r, the ErCx (effect on r concentration percentage), is defined to permit alternative population level estimation of a 'safe effect' concentration. |
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Keywords: | Life table Leslie Matrix Bootstrap Regression |
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