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Effects of polypropylene and polyethylene on the antioxidant system of the marine rotifer Brachionus koreanus
Summary
Exposing the marine rotifer Brachionus koreanus to polypropylene fragments and polyethylene beads showed that PP fragments increased intracellular reactive oxygen species and elevated antioxidant enzyme activity in a size- and concentration-dependent manner, while PE beads produced distinct oxidative stress profiles, with polymer type governing gene expression direction. The polymer- and shape-dependent oxidative toxicity in marine zooplankton highlights how different plastics pose distinct biological threats to the base of marine food webs, complicating broad ecological risk assessments.
Microplastic (MP) pollution is a global environmental concern due to their high production and improper management. Polypropylene (PP) and polyethylene (PE) are the most abundant MPs found in the coastal areas of South Korea. However, little information is available on the toxic effects of these environmentally relevant MPs on marine zooplankton. This study aimed to investigate the size- and shape-dependent toxicity of MPs in a marine rotifer. In this study, intracellular reactive oxygen species (ROS) content and antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT; and glutathione S-transferase, GST) were measured in the marine rotifer Brachionus koreanus after 24 h of exposure to small- and large-sized PP fragments and PE beads. Additionally, the transcriptional modulation of antioxidant enzyme-coding genes was examined using quantitative real-time polymerase chain reaction (qRT-PCR). Intracellular ROS level significantly increased with PP fragment in a size- and concentration-dependent manner, while it decreased with PE beads. Activities of SOD, CAT, and GST were elevated in most MP-exposed groups. PP fragments downregulated the mRNA expression of most antioxidant enzyme-coding genes, whereas PE beads upregulated their expression. These findings suggest that PP and PE can induce oxidative stress and exert size- and shape-dependent effects on antioxidant systems. This study will enhance our understanding of molecular mechanisms through which environmentally relevant MPs impact marine zooplankton.