Life-cycle parameters of Tisbe battagliai (Copepoda: harpacticoida) as indicators of chronic toxicity
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There is growing concern about the fate and biological effects of chemical contaminants in the marine environment. In the United Kingdom, the present ability to detect the potential long-term effects of contaminants is limited by the lack of suitable laboratory methods for measuring chronic toxicity. The harpacticoid copepod Tisbe battagliai was selected as a candidate test organism and a suite of chronic toxicity test methods was developed for measuring the effect of chemical contaminants on individual copepods (postembryonic development, reproduction and life-table analysis) and populations of T. battagliai. The development of chronic test methods proceeded alongside investigations of the influence of key environmental variables (temperature and food availability) on the biology of this species. These investigations provided a valuable insight into the potential importance of these environmental factors for influencing the development of populations of T. battagliai in the field, and helped to define the optimum conditions for the culture and chronic toxicity testing of this species in the laboratory. The methods were further evaluated using pentachlorophenol (PCP) as a reference toxicant and the aim was to investigate the potential interaction between toxicant (PCP), environmental factors (temperature and food availability), and their effects on the population dynamics of T. battagliai. In summary, results showed that temperature, and food quantity and quality, were important determinants of population dynamics. There were significant interactions between the chosen environmental variables (e.g. temperature), PCP, and subsequent biological effects on Tisbe battagliai, and results highlighted some important differences in toxicity testing approaches based on the measurement of individuals and populations of copepods. Established laboratory toxicity test procedures do not take account of the degree of complexity in the natural environment and this underlines the difficulty in extrapolating from laboratory. results to the field situation. In conclusion, the project was successful in its primary objective of developing a suite of techniques that can be used to measure the potential chronic toxicity of chemical contaminants in the marine environment. The methods using Tisbe battagliai are relatively simple to perform, are amenable to standardisation and provide relatively cost-effective measurements of chronic toxicity. The test methods can be used to provide chronic toxicity data but, more importantly, they can be used to address some of the current limitations associated with single species laboratory tests. For example, used in conjunction with key environmental variables, the methods provide a greater understanding of the potential interaction between contaminants and abiotic variables, thereby, improving the extrapolation of laboratory results to the field situation. The ability to carry out measurements on individual and populations of T. battagliai provides a valuable insight into the predictive links between effects at different levels of biological organisation.
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