Abstract
Recently, the effects of nanoplastics (NPs) on aquatic organisms have attracted much attention; however, research on the toxicity of NPs to microalgae has been insufficient. In the present study, the effects of polystyrene nanoplastics (nano-PS, 50 nm) on growth inhibition, chlorophyll content, oxidative stress, and algal toxin production of the marine toxigenic dinoflagellate Amphidinium carterae Hulburt were investigated. Chlorophyll synthesis was promoted by nano-PS on day 2 but was inhibited on day 4; high concentrations of nano-PS (≥50 mg/L) significantly inhibited the growth of A. carterae. Moreover, despite the combined effect of superoxide dismutase (SOD) and glutathione (GSH), high reactive oxygen species (ROS) level and malondialdehyde (MDA) content were still induced by nano-PS (≥50 mg/L), indicating severe lipid peroxidation. In addition, the contents of extracellular and intracellular hemolytic toxins in nano-PS groups were significantly higher than those in control groups on days 2 and 8, except that those of extracellular hemolytic toxins in the 100 mg/L nano-PS group decreased on day 8 because of severe adsorption of hemolytic toxins to the nano-PS. Hence, the effects of nano-PS on A. carterae are closely linked to nano-PS concentration and surface properties and exposure time. These findings provide a deep understanding of the complex effects of NPs on toxigenic microalgae and present valuable data for assessing their environmental risks.
Highlights
Plastic pollution in aquatic environments has recently gained attention worldwide.With the in-depth study of microplastics (MPs), nanoplastics (NPs) have drawn public awareness [1]
Owing to the cell membrane damage caused by the high reactive oxygen species (ROS) level, the content microalgae could limit the transfer of energy and nutrients, and the motility of the algal of extracellular hemolytic toxin in the nano-PS groups (10–80 mg/L) increased [19]
This can be attributed to the stress reaction of algae in adverse environments, in which the oxidative stress of nano-PS enhances the expression of toxic genes [18,23,54,55]
Summary
Plastic pollution in aquatic environments has recently gained attention worldwide. With the in-depth study of microplastics (MPs), nanoplastics (NPs) have drawn public awareness [1]. Nanoplastics, defined as plastic materials with at least one dimension on the nanoscale, have been found in natural waters and their concentrations are expected to continuously increase because of the degradation of primary micro(nano)plastics [2,3,4,5] Owing to their small size and large surface area, the ecological effects of NPs on aquatic organisms differ from those of large plastic particles [6]. In addition to growth inhibition effects, polystyrene nanoplastics (nano-PS) can reduce chlorophyll content and accelerate ROS production in algal cells [13]. Current research on the effects of NPs on the toxin production of harmful algal bloom species is still insufficient and unclear; for example, PS (100 nm) has no significant effect on the growth and photosynthetic activity of Microcystis aeruginosa, and promotes microcystin production only after 48 h. This research forms the basis for a more comprehensive evaluation of the toxicity of NPs to marine harmful algal bloom species and for the assessment of their environmental risks
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