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Effects of uranium on the energy budget and the population dynamics of Daphnia Magna

Sandrine Massarin, thesis defended on the 15th december 2010

Document type > *Mémoire/HDR/Thesis

Keywords >

Research Unit > IRSN/DEI/SECRE/LME

Authors > MASSARIN Sandrine

Publication Date > 15/12/2010


This work aimed to study effects of uranium on energy budget and population dynamics in Daphnia magna a representative microcrustacean of freshwater ecosystems. An experimental study of uranium toxicity on physiology (nutrition, respiration) and life history (survival, growth and reproduction) of D. magna was carried out, based on exposures over one, two or three successive generations (F0, F1 and F2) started with neonates from 1st or 5th brood, at 0, 10, 25 and 75 µgU.L-
. Results showed that toxic effects increased across generations (partially due to daphnid exposure during embryogenesis) and that individuals from 1st brood were more sensitive than individuals from 5th brood. Significant reductions in assimilation rates, measured using a radiotracing method with 14C-labelled food, allowed us to
identify an effect on assimilation as the mode of action for uranium, in agreement with important damages in the integrity of intestinal epithelium observed by optic microscopy. Integrating results in a dynamic energy budget model (DEBtox) yielded estimated no effect concentrations (NEC) of 9.37, 8.21 and 2.31 µgU.L-1 above which organism functions were altered in generations F0, F1 and F2, respectively. Combining DEBtox with matrix models allowed us to extrapolate consequences on asymptotic population growth rate (λ), a relevant endpoint in an ecological context. Simulations predicted an increase in uranium impact across generations with reduction of λ in F0 and population extinctions at 51-59 µgU.L-1 in F1 and 39-41 µgU.L-1 in F2. Simulations emphasized the importance of considering the most
sensitive individuals while determining population response.




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