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Nanoplastics and their combined effects with sulphamethoxazole on the free-floating aquatic plant Lemna major
Summary
Researchers examined the combined effects of nanoplastics and the antibiotic sulphamethoxazole on free-floating algae, assessing whether nanoplastics alter antibiotic toxicity. The co-exposure produced greater inhibitory effects on algal growth than either substance alone.
The exponential growth of plastic production has led to a diffuse contamination of ecosystems. Plastic debris is continuously released into the aquatic environment and it gradually degrades into micro- (1 to 5,000 μm) and nano-scaled (¡ 1 μm) particles. Owing to the large surface area per unit mass, nanoplastics (NPs) show a considerably higher adsorption capacity than the original bulk material, thus acting as vectors for harmful organic contaminants, with unknown ecotoxicological effects on aquatic biota. The widespread of pharmaceuticals, including antibiotics (ABs), is another urgent issue that requires immediate attention. Therefore, the combined ecotoxicity of NPs and ABs can have significant and largely disregarded implications for environmental health. In this context, this study focused on the ecotoxicity of polystyrene NPs and the antibiotic sulfamethoxazole (SMX, commonly used for urinary and respiratory infections) on an aquatic common plant. Different concentrations of NPs and SMX (from 100 to 5 mg/L) were tested to assess their ecotoxicological effects on Lemna major (ISO 20227:2017), a free-floating aquatic plant with well-known contaminant accumulation and purifying capabilities. EC50 values and chlorophyll content in plants were determined for each contaminant and mixture. The Flow cytometry was used for NPs quantification and characterization and for assessing microbial cell abundance in a mineral growth media. The results showed a correlation between the concentration of the contaminants (NPs and SMX) and their combined effects on plant growth. Higher concentrations had more pronounced negative effects, indicating that both, dosage and exposure time, represent critical ecotoxicological factors. Moreover, NPs tended to aggregate over the incubation time, suggesting different plant responses to aggregated NPs than to their dispersed forms. Finally, the combined toxicity of NPs and SMX was likely higher than their individual effects, leading to a more severe impairment of plant health and growth. Also see: https://micro2024.sciencesconf.org/558872/document