Influence of temperature on the regulation and toxicity of zinc in Folsomia candida (Collembola).
To generate reproducible and reliable results, most protocols for standardized toxicity tests prescribe strict limits for test conditions such as temperature and relative humidity. In the field, however, variability of climate can influence the functioning of organisms and induce changes in sensitivity. To evaluate the influence of temperature on the ecotoxicity of zinc, the springtail Folsomia candida was exposed to zinc-contaminated soil at different temperatures. In one experiment, the toxicity of ZnCl2 was determined at a constant temperature and under alternating temperature conditions. Although control performance of F. candida was influenced by the temperature treatment, effect concentrations for reproduction were not significantly different between treatments. Levels of internal zinc regulation were higher in animals exposed to alternating temperatures. Based on the observed influence of temperature on the accumulation of zinc, a second experiment was performed to determine the sensitivity of F. candida to zinc at four different exposure temperatures. A decrease in temperature led to an increase in sensitivity when sublethal parameters such as growth and reproduction were considered. However, animals were less sensitive at lower temperatures where mortality was concerned. Internal zinc concentrations in the animals increased with decreasing temperatures, and when the effect on reproduction was based on internal zinc levels, differences between temperature treatments were not significant. From the results of this study it is concluded that for F. candida, constant temperature conditions form a good basis for the extrapolation of toxicity levels to fluctuating temperature conditions. Since the average exposure temperature can alter the sensitivity of F. candida for zinc, and changes in sensitivity are parameter dependent, exposure temperature should be chosen carefully.
Smit
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Department of Ecology and Ecotoxicology, Vrije Universiteit, Amsterdam, The Netherlands. smit@bio.vu.nl
Van Gestel
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D000818:Animals; D003080:Cold Temperature; D006358:Hot Temperature; D007313:Insecta / Q000187:drug effects*; D012098:Reproduction / Q000187:drug effects; D012989:Soil Pollutants / Q000633:toxicity; D016019:Survival Analysis; D018675:Toxicity Tests; D015032:Zinc / Q000633:toxicity*
D012989:Soil Pollutants; D015032:Zinc