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<p>Metal discharges from anthropogenic activities are of great concern, and the effects of metallic mixtures in aquatic environments are still not fully understood. This study aimed to evaluate the effects of cadmium (Cd) and copper (Cu), isolated and combined, in the growth and photosynthesis – photosystem II (PSII) activity (Φ<sub>PSII</sub> = F<sub>v</sub>/F<sub>M</sub>), effective quantum yield, photochemical (qP) and non-photochemical quenching (qN and NPQ), and quenchings of regulated ((Y(NPQ)) and non-regulated ((Y(NO)) non-photochemical energy loss in photosystem II, in addition to the rapid light curves of the freshwater green microalga <i>Ankistrodesmus densus</i>. Both metals affected algal physiology and when combined most of the responses were antagonists, i.e., the observed effects were lower than those predicted for the mixture. The contaminants decreased the chlorophyll <i>a</i> production, photosynthetic activity, and increased heat dissipation, suggesting activation of the photoprotection mechanisms and with no evidence of photoprotection damage in the algae. Except for Y(NO), all evaluated photosynthetic parameters were sensitive indicators of the changes observed in microalgae under Cd and Cu exposure, isolated or combined. In addition, we suggest that algal protective mechanisms were efficient to decrease the impact of the combination of metals, reinforced by the increases in qN, NPQ and Y(NPQ), resulting mainly in antagonism in photosynthetic parameters.</p>

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Effects of copper and cadmium mixtures on photosynthetic parameters of the freshwater microalga Ankistrodesmus densus (Chlorophyceae)

  • 期刊论文

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  • 发表日期：

    2025年9月3日

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  • Giseli Swerts Rocha,
  • Ana Teresa Lombardi,
  • Evaldo L. G. Espíndola

摘要

Metal discharges from anthropogenic activities are of great concern, and the effects of metallic mixtures in aquatic environments are still not fully understood. This study aimed to evaluate the effects of cadmium (Cd) and copper (Cu), isolated and combined, in the growth and photosynthesis – photosystem II (PSII) activity (ΦPSII = Fv/FM), effective quantum yield, photochemical (qP) and non-photochemical quenching (qN and NPQ), and quenchings of regulated ((Y(NPQ)) and non-regulated ((Y(NO)) non-photochemical energy loss in photosystem II, in addition to the rapid light curves of the freshwater green microalga Ankistrodesmus densus. Both metals affected algal physiology and when combined most of the responses were antagonists, i.e., the observed effects were lower than those predicted for the mixture. The contaminants decreased the chlorophyll a production, photosynthetic activity, and increased heat dissipation, suggesting activation of the photoprotection mechanisms and with no evidence of photoprotection damage in the algae. Except for Y(NO), all evaluated photosynthetic parameters were sensitive indicators of the changes observed in microalgae under Cd and Cu exposure, isolated or combined. In addition, we suggest that algal protective mechanisms were efficient to decrease the impact of the combination of metals, reinforced by the increases in qN, NPQ and Y(NPQ), resulting mainly in antagonism in photosynthetic parameters.