[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA | International audience | The toxicity of dietary exposure to artificially aged TiO2 nanomaterial (T-Lite (TM)) used in sunscreen cream was studied on D. magna. Pseudokirchneriella subcapitata cultures were contaminated with TiO2-residues, obtained by artificial aging. Significant association of TiO2-residues on algae was detected by X-ray fluorescence spectromicroscopy. A D. magna dietary chronic exposure of these contaminated algae with TiO2-residues was performed. X-ray chemical imaging revealed that Ti was localized only in the digestive tract of the daphnia. Chronic exposure of daphnia to by-product of aged TiO2 nanoparticles brought by food induced low mortality but decreased growth and reproduction which can be partly related to the modification of the digestive physiology of daphnia. This study demonstrated that the assessment of the ecotoxicological impact of nanomaterials in aquatic environment should take into account the aging of these materials which can further influence their bioavailability for aquatic organisms.

The present study was undertaken to assess the impact of a candidate mosquito larvicide, spinosad (8, 17 and 33 μg L−1) on a field population of Daphnia magna under natural variations of water temperature and salinity, using Bti (0.16 and 0.50 μL L−1) as the reference larvicide. Microcosms (125 L) were placed in a shallow temporary marsh where D. magna was naturally present. The peak of salinity observed during the 21-day observation period may have been partly responsible for the decrease of daphnid population density in all the microcosms. It is also probably responsible for the absence of recovery in the microcosms treated with spinosad which caused a sharp decrease of D. magna abundance within the first two days following treatment whereas Bti had no effect. These results suggest that it may be difficult for a field population of daphnids to cope simultaneously with natural (water salinity and temperature) and anthropogenic (larvicides) stressors. Significant interaction between salinity and spinosad exposure impairs the recovery of a natural population of Daphnia magna