title: Interactive effects of copper oxide nanoparticles and light to green alga Chlamydomonas reinhardtii.
abstract: The present study explores the effect of light with different spectral composition on the stability of CuO-nanoparticle (CuO-NP) dispersions and their effects to green alga Chlamydomonas reinhardtii. The results showed that simulated natural light (SNL) and light with enhanced UVB radiation (UVR*) do not affect the dissolution of CuO-NPs as compared to light irradiation conditions typically used in laboratory incubator (INC). Comparable values of ζ-potential and hydrodynamic size during 24h were found under all studied conditions. Concentrations of CuO-NPs below 1mgL(-1) do not attenuate the light penetration in the algal suspensions in comparison with NP-free system. Exposure to a combination of 8μgL(-1) or 0.8mgL(-1) CuO-NPs and INC or SNL has no significant effect on the algal growth inhibition, algal fluorescence and membrane integrity under short-term exposure. However, an enhancement of the percentage of cells experiencing oxidative stress was observed upon exposure to 0.8mgL(-1) CuO-NPs and SNL for 4 and 8h. Combination of UVR* and 0.8mgL(-1) CuO-NPs resulted in synergistic effects for all biological endpoints. Despite the photocatalytic properties of CuO-NPs no significant increase in abiotic reactive oxygen species (ROS) production under simulated solar radiation was observed suggesting that the synergistic effect observed might be correlated to other factors than CuO-NP-mediated ROS photoproduction. Tests performed with CuSO4 confirmed the important role of dissolution as toxicity driving force for lower CuO-NP concentration. However, they failed to clarify the contribution of dissolved Cu on the combined effects at 0.8mgL(-1) CuO-NPs. The results point out the necessity of taking into account the possible interactions between ENPs and changing light conditions when evaluating the potential effects of ENPs to phytoplankton in natural waters.
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, 10 route de Suisse, CH-1290 Versoix, Switzerland.
authors.forename: Giulia
authors.initials: G
authors.lastname: Cheloni
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, 10 route de Suisse, CH-1290 Versoix, Switzerland.
authors.forename: Elodie
authors.initials: E
authors.lastname: Marti
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, 10 route de Suisse, CH-1290 Versoix, Switzerland. Electronic address: vera.slaveykova@unige.ch.
authors.forename: Vera I
authors.initials: VI
authors.lastname: Slaveykova
mesh_terms: D002463:Cell Membrane Permeability / Q000187:drug effects; D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D003300:Copper / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects* / Q000528:radiation effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity*
chemical_list: D017382:Reactive Oxygen Species; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D003300:Copper; C000520:cuprous oxide
keywords: Abiotic ROS; Combined stress; Copper oxide nanoparticles; Light irradiation; Oxidative stress; Shading