Single and combined effects of Zn and Al on photosystem II of the green microalgae Raphidocelis subcapitata assessed by pulse-amplitude modulated (PAM) fluorometry

Author(s)

Gebara, Renan Castelhano ; Alho, Lays de Oliveira Gondalves ; Mansano, Adrislaine da Silva ; Rocha, Giseli Swerts ; Melao, Maria da Grada Gama

• Document type: Journal article
• Source: AQUATIC TOXICOLOGY; v. 254, p. 10-pg., 2022-12-08.

Abstract

Increasing metal concentrations in aquatic environments are mainly due to anthropogenic actions, which is a matter of concern for the biodiversity of aquatic biota. It is known that metals coexist in environments, however environmental risk assessments do not usually take into account the effects of these mixtures. We aimed to test Zn and Al mixtures on the photosynthetic apparatus of a green microalga, for the first time, using PAM fluorometry. After 72 h exposure, single concentrations from 0.08 to 0.46 mu M Zn and 22.24 to 37.06 mu M Al affected the photosynthetic parameters of Raphidocelis subcapitata. Metals affected the efficiency of the oxygen-evolving complex - OEC (F0/Fv), increasing it by 25% at 0.46 mu M Zn and by 82% at 37.06 mu M Al - concentrations where, 57% and 78% of growth inhibition occurred, respectively. We observed that the algal growth was more sensitive to infer Zn toxicity, while F0/Fv was more affected by Al. Regarding quenching, there was an increase in passive energy dissipation ((Y(NO)) at 0.46 mu M Zn, and we observed an increase in both regulated ((NPQ and Y(NPQ)) and non-regulated energy dissipation ((qN and (Y(NO)) at 37.06 mu M Al. Our results showed synergism and antagonism at different concentrations in mixtures, the antagonism prevailing at higher metal concentrations and, in some cases, synergism at lower concentrations of Zn and Al. Since we observe more than additive and less than additive effects, it is of the utmost importance to take mixture toxicity tests into account when performing risk assessments on green algae. (AU)

• FAPESP's process: 21/13583-0 - Ecotoxicological Effects of Nanoparticles of ZnWO4 and CuWO4 On a Freshwater Planktonic Foodchain: Evaluating Possible Environmental Impacts of Emerging Contaminants
• Grantee: Renan Castelhano Gebara
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 16/00753-7 - Toxic effects of emerging microcontaminants on planktonic food webs
• Grantee: Maria da Graça Gama Melão
• Support Opportunities: Regular Research Grants
• FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 14/14139-3 - Microbial processes and biodiversity in aquatic ecosystems
• Grantee: Hugo Miguel Preto de Morais Sarmento
• Support Opportunities: Research Grants - Young Investigators Grants