Algae response to engineered nanoparticles: current understanding, mechanisms and implications

The growing application of nanotechnology causes the release of engineered nanoparticles (NPs) into aquatic environments. With increasing concerns over the potential effect of NPs on aquatic organisms, investigations on NP toxicity to algae are rising. To date, the overall algal response to cope with NP toxicity is still uncertain. In this review, a meta-analysis was conducted to quantitatively assess the toxicity mechanisms dominated by oxidative stress. The reactive oxygen species elevated by 90% caused retarded algal growth by reduction (38%) in cell density, and NP toxicity was strongly dependent on the NP type and dose. Specifically, the mechanisms of NP toxicity were discussed in different omics levels. Further, we summarized the current knowledge and mechanisms of defense strategies, including formation of a protective bio-barrier and adjustment in intracellular processes (internalization, transformation and compartmentation) to decrease cellular NP concentrations. Based on the response patterns of algae to NPs, we addressed the possibility of NP application for algal bloom control. A systematic understanding of algal response mechanisms to NPs will help develop safe and sustainable nanotechnology in aquatic ecosystems.