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Microalgae need a variety of nutrients for optimal growth and health. However, this rarely occurs in nature, and if nutrient proportions vary, biochemical changes can occur in phytoplankton community. This may result in modifications of zooplankton food quality, affecting aquatic food chains. Our aim was to investigate the toxicity of copper (Cu) to Selenastrum gracile , a common freshwater Chlorophyceae, at different physiological status induced by varying phosphorus (P) concentration in culture medium. Phosphorus was investigated at 2.3×10 −4 , 1.1×10 −4 , 2.3×10 −5 , 4.6×10 −6 and 2.3×10 −6 mol L −1 and Cu at six concentrations, ranging from 6.9×10 −9 mol L −1 to 1.0×10 −7 mol L −1 free Cu 2+ ions. To guarantee the cells would be in a physiological status that reflected the external P concentration, they were previously acclimated up to constant growth rate at each P concentration. Phosphorus acclimated cells were then exposed to Cu and toxicity was evaluated through population density, growth rates and chlorophyll a content. Free Cu 2+ ions concentrations were calculated through the chemical equilibrium model MINEQL + . The results showed that higher Cu toxicity was obtained in P-limited than in P-replete cells, and that chlorophyll a /cell was higher in P-limited cells and excess Cu than in P-replete cells. This confirms the importance of microalgae nutritional status to withstand the negative effects of the trace metal. [ABSTRACT FROM AUTHOR]

Abstract: The present study aimed to investigate the response of several life history parameters (body length and age of primipara, duration of embryonic development, maximum body length, reproduction and survival) of the zooplankton Ceriodaphnia silvestrii while exposed to copper contaminated algae Pseudokirchneriella subcapitata. In order to evaluate chronic exposure on the animal's life history, long-term experimental design was used. Cladocerans were fed with a dietary copper concentration ranging from 3 to 68fgCucell−1. Low waterborne copper exposure (around 10−10 molL−1 free Cu2+ ions) was kept in the experiments. The results showed that by exposure of cladocerans during 7 days to contaminated food with 68fgCucell−1, a significant reduction in neonate production, survival and body size were obtained. Inhibition on egg production of zooplankton at 38fgCucell−1 were observed in 36 days chronic dietary copper exposure. The importance of entire life cycle study to better evaluate cladoceran responses to chronic dietary metal exposure was demonstrated. [Copyright &y& Elsevier]