title: Fast algal eco-toxicity assessment: Influence of light intensity and exposure time on Chlorella vulgaris inhibition by atrazine and DCMU.
abstract: In order to develop a rapid assay suitable for algal eco-toxicity assessments under conditions representative of natural ecosystems, this study evaluated the short-term (<1h) response of algae exposed to atrazine and DCMU using oxygen productivity measurements. When Chlorella vulgaris was exposed to these herbicides under 'standard' low light intensity (as prescribed by OECD201 guideline), the 20min-EC50values recorded via oxygen productivity (atrazine: 1.32±0.07μM; DCMU: 0.31±0.005μM) were similar the 96-h EC50recorded via algal growth (atrazine: 0.56μM; DCMU: 0.41μM), and within the range of values reported in the literature. 20min-EC50 values increased by factors of 3.0 and 2.1 for atrazine and DCMU, respectively, when light intensity increased from 60 to 1400μmolm-2s-1of photosynthetically active radiation, or PAR. Further investigation showed that exposure time significantly also impacted the sensitivity of C. vulgaris under high light intensity (>840μmolm-2s-1as PAR) as the EC50for atrazine and DCMU decreased by up to 6.2 and 2.1 folds, respectively, after 50min of exposure at a light irradiance of 1400μmolm-2s-1as PAR. This decrease was particularly marked at high light intensities and low algae concentrations and is explained by the herbicide disruption of the electron transfer chain triggering photo-inhibition at high light intensities. Eco-toxicity assessments aiming to understand the potential impact of toxic compounds on natural ecosystems should therefore be performed over sufficient exposure times (>20min for C. vulgaris) and under light intensities relevant to these ecosystems.
authors.affiliation: School of Engineering and Advanced Technology, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Camuel
authors.affiliation: School of Engineering and Advanced Technology, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand. Electronic address: B.J.Guieysse@massey.ac.nz.
authors.forename: Benoit
authors.initials: B
authors.lastname: Guieysse
authors.affiliation: School of Engineering and Advanced Technology, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand; Department of Chemical Engineering and Environmental Technology, Valladolid University, Spain.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Alcántara
authors.affiliation: School of Engineering and Advanced Technology, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand; INRIA BIOCORE, BP 93 06902 Sophia Antipolis Cedex, France.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Béchet
mesh_terms: D001280:Atrazine / Q000633:toxicity*; D048408:Chlorella vulgaris / Q000187:drug effects* / Q000528:radiation effects; D004237:Diuron / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D054750:Ecotoxicology; D004784:Environmental Monitoring / Q000379:methods*; D008027:Light; D010100:Oxygen / Q000032:analysis*; D010788:Photosynthesis / Q000187:drug effects; D013997:Time Factors; D018675:Toxicity Tests / Q000379:methods; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D004237:Diuron; D001280:Atrazine; D010100:Oxygen
keywords: Eco-toxicity; Herbicide; Micro-algae; Photoinhibition; Photosynthesis