title: The interactive effects of microcystin-LR and cylindrospermopsin on the growth rate of the freshwater algae Chlorella vulgaris.
abstract: Microcystin-LR (MC-LR) and cylindrospermopsin (CYN) are the most representative cyanobacterial cyanotoxins. They have been simultaneously detected in aquatic systems, but their combined ecotoxicological effects to aquatic organisms, especially microalgae, is unknown. In this study, we examined the effects of these cyanotoxins individually and as a binary mixture on the growth rate of the freshwater algae Chlorella vulgaris. Using the MIXTOX tool, the reference model concentration addition (CA) was selected to evaluate the combined effects of MC-LR and CYN on the growth of the freshwater green algae due to its conservative prediction of mixture effect for putative similar or dissimilar acting chemicals. Deviations from the CA model such as synergism/antagonism, dose-ratio and dose-level dependency were also assessed. In single exposures, our results demonstrated that MC-LR and CYN had different impacts on the growth rates of C. vulgaris at the highest tested concentrations, being CYN the most toxic. In the mixture exposure trial, MC-LR and CYN showed a synergistic deviation from the conceptual model CA as the best descriptive model. MC-LR individually was not toxic even at high concentrations (37 mg L(-1)); however, the presence of MC-LR at much lower concentrations (0.4-16.7 mg L(-1)) increased the CYN toxicity. From these results, the combined exposure of MC-LR and CYN should be considered for risk assessment of mixtures as the toxicity may be underestimated when looking only at the single cyanotoxins and not their combination. This study also represents an important step to understand the interactions among MC-LR and CYN detected previously in aquatic systems.
authors.affiliation: Departamento de Biologia & CESAM, Universidade de Aveiro, 3810-193, Aveiro, Portugal. carlos.pinheiro@ua.pt.|Centro Interdisciplinar de Investigação Marinha e Ambiental, CIIMAR/CIMAR, Rua dos Bragas 289, 4050-123, Porto, Portugal. carlos.pinheiro@ua.pt.
authors.forename: Carlos
authors.identifier: http://orcid.org/0000-0003-3170-9533
authors.initials: C
authors.lastname: Pinheiro
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental, CIIMAR/CIMAR, Rua dos Bragas 289, 4050-123, Porto, Portugal.|Escola Superior de Tecnologia da Saúde do Porto, Rua Valente Perfeito, 322, 440-330, Vila Nova de Gaia, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Azevedo
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental, CIIMAR/CIMAR, Rua dos Bragas 289, 4050-123, Porto, Portugal.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Campos
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental, CIIMAR/CIMAR, Rua dos Bragas 289, 4050-123, Porto, Portugal.|Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4069-007, Porto, Portugal.
authors.forename: Vítor
authors.initials: V
authors.lastname: Vasconcelos
authors.affiliation: Departamento de Biologia & CESAM, Universidade de Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: Susana
authors.initials: S
authors.lastname: Loureiro
mesh_terms: D000470:Alkaloids; D001427:Bacterial Toxins / Q000032:analysis / Q000633:toxicity*; D048408:Chlorella vulgaris / Q000187:drug effects / Q000254:growth & development*; D000087522:Cyanobacteria Toxins; D004784:Environmental Monitoring; D005618:Fresh Water; D008387:Marine Toxins; D052998:Microcystins / Q000032:analysis / Q000633:toxicity*; D014498:Uracil / Q000031:analogs & derivatives* / Q000032:analysis / Q000633:toxicity; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D000470:Alkaloids; D001427:Bacterial Toxins; D000087522:Cyanobacteria Toxins; D008387:Marine Toxins; D052998:Microcystins; D014874:Water Pollutants, Chemical; C089595:cylindrospermopsin; D014498:Uracil; C057862:cyanoginosin LR
keywords: Chlorella vulgaris; Concentration addition; Cyanotoxins; Cylindrospermopsin; Microcystin-LR; Synergism