Photosynthetic, morphological and biochemical biomarkers as tools to investigate copper oxide nanoparticle toxicity to a freshwater chlorophyceae

• Published in: Environmental pollution (1987) 2020-10, Vol.265, p.114856-114856, Article 114856
• Main Authors: Alho, Lays de Oliveira Gonçalves, Souza, Jaqueline Pérola, Rocha, Giseli Swerts, Mansano, Adrislaine da Silva, Lombardi, Ana Teresa, Sarmento, Hugo, Melão, Mariada Graça Gama
• Format: Article
• Language: English
• Subjects: Energy reserves; Lipid classes; Metallic nanoparticles; Photosynthetic activity; Raphidocelis subcapitata
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2020.114856

Copper oxide nanoparticles (CuO NP) have been produced on a large scale due to their economically interesting thermophysical properties. This heightens the concern about risks they may pose on their release into the environment, possibly affecting non-target organisms. Microalga are important organisms in ecotoxicological studies as they are at the base of the aquatic food chain, but information about their biochemical and photosynthetic changes in response CuO NP are still scarce. We studied the effects of CuO NP in Raphidocelis subcapitata using morphological, photosynthetic and biochemical biomarkers. Our results showed that the NP affected microalgal population growth with 0.70 mg Cu L−1 IC50–96 h (inhibition concentration). Based on predicted environmental concentrations of Cu NPs in aquatic environments, our results indicate potential risks of the NP to microalgae. Algal cell size, granularity and photosynthetic efficiencies were affected by the CuO NP at 0.97 and 11.74 mg Cu L−1. Furthermore, lipid metabolism was affected mostly at the highest NP concentration, but at environmentally relevant values (0.012 and 0.065 mg Cu L−1) the production of sterols (structural lipids) and triacylglycerols (reserve lipid) increased. Moreover, we found evidence of cell membrane impairment at the highest CuO NP concentration, and, as a photosynthetic response, the oxygen evolving complex was its main site of action. To the best of our knowledge, this is the first study to date to investigate microalgal lipid composition during CuO NP exposure, showing that it is a sensitive diagnostic tool. This research demonstrated that CuO NP may affect the physiology of R. subcapitata, and because they were observed in a primary producer, we foresee consequences to higher trophic levels in aquatic communities. [Display omitted] •CuO NP led to increased cell size and granularity of R. subcapitata.•High CuO NP concentrations impaired the photosynthetic activity in R. subcapitata.•Energy reserve compounds increased in response to CuO NP.•Increase in structural lipids suggests cell membrane reinforcement.•Ionic copper and CuO NP toxicity share common features in microalgae response. CuO NP damaged R. subcapitata cell division process impaired the photosynthetic activity and induced biochemical changes, particularly affecting lipid class composition.