Temperature influence on silver nanoparticles inhibitory effect on photosystem II photochemistry in two green algae, Chlorella vulgaris and Dunaliella tertiolecta

Abstract

In this study, the effect of silver nanoparticles (AgNPs) on the photosynthetic performance of two green algae, Chlorella vulgaris and Dunaliella tertiolecta, was investigated at 25°C and 31°C. To induce AgNPs effect, algal cells were exposed for 24 h to concentrations varying from 0 to 10 mg/L. The polyphasic OJIP fluorescence transient was used to evaluate photosystem II (PSII). We show that growth media and temperature had different effects in AgNPs agglomerates formation and Zeta potential. When temperature conditions change, inhibitory effect of AgNPs also undergoes changes. Increase of temperature induced higher altering effects to PSII quantum yield, primary photosynthetic electron transport, and consequently higher decrease of total photosynthetic performance if compared to AgNPs effect alone. AgNPs has a negative effect on D. tertiolecta compared to C. vulgaris. We conclude that temperature tends to enhance the toxic effects on aquatic alga and these alterations might have serious consequences on ecosystem equilibrium and aquatic plant communities.