Phytotoxicity of silver nanoparticles to aquatic plants, algae and micro-organisms

Silver nanoparticles (Ag NPs) can easily leak into the aquatic environment and, depending on the environmental conditions, readily transform. Since ionic silver is considered one of the most toxic ions for aquatic organisms, there is a growing concern about the effects of Ag NPs on the aquatic ecosystem. Aquatic organisms are very sensitive to pollutants, but the fate and concentrations of Ag NPs in water are still unknown. Data shows that even low concentrations of Ag NPs could affect aquatic photosynthetic organisms, and the size and shape of nanoparticles plays a central role in Ag NP toxicity. Ag NP toxicity is not fully attributable to released ions: many studies show that in photosynthetic organisms silver ions and Ag NPs caused similar effects, although silver ions were often active at lower concentrations. Toxicity of Ag NPs may be caused by a Trojan-horse type of mechanism, in which nanoparticles are internalized within cells where they can release silver ions. In photosynthetic aquatic organisms, one of the main targets of Ag NPs is the photosynthetic apparatus. AgNPs can also lead to an increase in oxidative stress through reactive oxygen species production. Ag NPs can modify the composition of a natural community of aquatic microorganisms, such as phytoplankton, and accumulate in the food chain, even if the potential for their biomagnification remains unclear.