Aquatic Toxicology 99 (2010) 309–319 Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox Effects of chronic uranium exposure on life history and physiology of Daphnia magna over three successive generations Sandrine Massarin a , Frédéric Alonzo a,∗ , Laurent Garcia-Sanchez a , Rodolphe Gilbin b , Jacqueline Garnier-Laplace c , Jean-Christophe Poggiale d a Laboratoire de Modélisation Environnementale, Institut de Radioprotection et de Sûreté Nucléaire, Cadarache, Bat 159, BP3, 13115 Saint-Paul-lez-Durance Cedex, France b Laboratoire de Radioécologie et d’Ecotoxicologie, Institut de Radioprotection et de Sûreté Nucléaire, Cadarache, Bat 186, BP3, 13115 Saint-Paul-lez-Durance Cedex, France c Service d’Etude du Comportement des Radionucléides dans les Ecosystèmes, Institut de Radioprotection et de Sûreté Nucléaire, Cadarache, Bat 159, BP3, 13115 Saint-Paul-lez-Durance Cedex, France d Laboratoire de Microbiologie, Géochimie et Ecologie Marines (UMR CNRS 6117), Centre d’Océanologie de Marseille, Université de la Méditerranée, Campus de Luminy, Case 901, Marseille Cedex 9, 13288, France article info Article history: Received 11 February 2010 Received in revised form 4 May 2010 Accepted 8 May 2010 Keywords: Daphnia magna Uranium Multigeneration Recovery Energy budget abstract Daphnia magna was exposed to waterborne uranium (U) at concentrations ranging from 10 to 75 gL -1 over three successive generations (F0, F1 and F2). Progeny was either exposed to the same concentration as mothers to test whether susceptibility to this radioelement might vary across generations or returned to a clean medium to examine their capacity to recover after parental exposure. Maximum body burdens of 17, 32 and 54 ng U daphnid -1 were measured in the different exposure conditions and converted to corresponding internal alpha dose rates. Low values of 5, 12 and 20 Gy h -1 suggested that radiotoxicity was negligible compared to chemotoxicity. An increasing sensitivity to toxi- city was shown across exposed generations with significant effects observed on life history traits and physiology as low as 10 gL -1 and a capacity to recover partially in a clean medium after parental exposure to ≤25 gL -1 . Using a 14 C-labelled food technique, the study showed that uranium affected carbon assimilation in F0 at concentrations of 25 and 75 gL -1 (34 and 80% reduction respectively) and as low as 10 gL -1 in F1 and F2 (40 and 36% reduction respectively). Consequences were strong for both somatic growth and reproduction and increased in severity across generations. Maximum size was reduced by 12% at 75 gL -1 in F0 and 23% at 25 gL -1 in F2. Reduction in 21-day fecundity ranged from 27 to 48% respectively at 25 and 75 gL -1 in F0 and from 43 to 71% respectively at 10 and 25 gL -1 in F2. Growth retardation caused a delay in deposition of first brood of 1.3 days at 75 gL -1 in F0, of 1.9 days at 25 gL -1 in F1 and of 5 days at 25 gL -1 in F2. Differences in respiration rates and egg dry mass between the control and exposed daphnids were mainly an indirect result of uranium effect on body size. The observed increase in toxic effects across generations indicated the necessity of carrying out multi- generation tests to assess environmental risk of uranium in daphnids. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Uranium (U), a naturally occurring radioactive metal, is present in freshwaters at trace concentrations from 0.02 to 6 gL -1 and may increase up to 2 mg L -1 in the vicinity of uraniferous sites (Bonin and Blanc, 2001; WHO, 2001). Anthropogenic activities mainly associated with the use of uranium as nuclear fuel (uranium mining, milling and refining as well as spent fuel reprocess- ing) contribute to uranium redistribution in freshwaters and may cause water concentrations to exceed background concentrations ∗ Corresponding author. Fax: +33 4 42 19 91 43. E-mail address: frederic.alonzo@irsn.fr (F. Alonzo). (Ragnarsdottir and Charlet, 2000). As a consequence, uranium has become of increasing concern for biota protection over the past decades (Environment Canada, 2003; Sheppard et al., 2005). In fact, natural uranium causes both a chemical and radiological hazard to aquatic ecosystems, because of its toxicity as a metal and as a mixture of three alpha-emitting radioisotopes along with their pro- genies ( 234 U, 235 U and 238 U, in relative abundance of 0.005, 0.720 and 99.275%; Weigel, 1986). To address these hazards, toxicity of uranium has been inten- sively studied in a wide range of freshwater species, including benthic and pelagic invertebrates as well as fish. Reported effects have covered many different endpoints which concern levels of bio- logical organisation from subcellular damages to perturbations in physiology and life history of organisms: reduced hepatic antiox- 0166-445X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2010.05.006