Fragment-Shaped Microplastics Induce Size- and Polymer-Dependent Physiological and Gut Microbial Responses in Mytilus edulis
Polystyrene microplastics can induce oxidative stress and alter gut microbiota in Mytilus edulis, highlighting potential ecological risks.
Where it sits
this study against the rest of the glutathione (gsh) corpusSummary and findings
This study investigated the physiological and gut microbial responses of Mytilus edulis to fragment-shaped microplastics of varying sizes and polymers. The mussels exhibited rapid ingestion of microplastics, with specific peak abundances reported. Physiological stress markers and gut microbiota shifts were observed following exposure to polystyrene microplastics.
Abstract
<title>Abstract</title> <p> Microplastics (MPs) are pervasive pollutants in marine ecosystems and pose risks to aquatic organisms. The blue mussel ( <italic>Mytilus edulis</italic> ) is widely used as a sentinel species for microplastic studies. This study investigated the accumulation of fragment-shaped microplastics of different polymers—polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC)—and sizes (100–200 µm, 200–300 µm, 300–500 µm) in mussels, and assessed physiological and gut microbial responses to 300–500 µm PS MPs. Short-term exposure revealed rapid ingestion of all microplastic types, with peak abundances at 2 hours for PET (0.7–1.87 items/g) and PVC (0.55–1.5 items/g), and at days 4–5 for PS (2.92–6.63 items/g). Smaller fragments (100–200 µm) were ingested more readily but excreted efficiently, whereas larger fragments (300–500 µm) were retained longer. PS microplastics induced oxidative stress: superoxide dismutase (SOD) and catalase (CAT) peaked at 87.3 U/mg and 62.5 U/mg on day 7, while reduced glutathione (GSH) decreased to 3.2 µmol/g. Digestive enzymes were affected: α-amylase increased to 48.6 U/mg, while trypsin and pepsin decreased to 12.5 U/mg and 15.2 U/mg before partial recovery. Gut microbiota shifts were observed at phylum (Proteobacteria, Verrucomicrobia, Bacteroidetes) and genus levels ( <italic>Rubritalea</italic> , <italic>Mycoplasma</italic> , <italic>Arcobacter</italic> ), with reduced Chao1 and Shannon indices (p < 0.05). Principal Coordinate Analysis confirmed substantial compositional changes across exposure stages. These results indicated that microplastic size and polymer type jointly regulate accumulation in mussels, and that PS MPs cause multi-dimensional physiological stress and gut microbiota disruption, highlighting potential ecological risks for bivalves. </p>
Background
Microplastics are a significant environmental concern, particularly in marine ecosystems where they can affect aquatic organisms. Mytilus edulis serves as a model organism for studying the impact of microplastics due to its ecological relevance. This study aims to elucidate the physiological and microbial responses of mussels to different types and sizes of microplastics, contributing to the understanding of ecological risks posed by these pollutants.
Methods
The study utilized Mytilus edulis as the model organism, exposing them to fragment-shaped microplastics of varying polymers (PET, PS, PVC) and sizes (100–200 µm, 200–300 µm, 300–500 µm). The exposure duration was short-term, with assessments made at various time points, including 2 hours and days 4–5. Primary outcomes included ingestion rates, oxidative stress markers, digestive enzyme activity, and gut microbiota composition.
Results
The primary endpoint observed was the peak abundance of PS microplastics at 2.92–6.63 items/g at days 4–5. SOD and CAT levels indicated oxidative stress, with SOD peaking at 87.3 U/mg and CAT at 62.5 U/mg on day 7. GSH levels decreased to 3.2 µmol/g, while digestive enzyme activities showed varied responses, with α-amylase increasing to 48.6 U/mg and trypsin and pepsin decreasing to 12.5 U/mg and 15.2 U/mg respectively.
Interpretation
The findings suggest that microplastic size and polymer type significantly influence accumulation and physiological stress in Mytilus edulis. While the statistical significance of the results is noted, the clinical relevance in terms of ecological impact requires further investigation. Limitations such as short exposure duration and lack of long-term data may confound the conclusions drawn regarding the ecological risks of microplastics.
Key findings
- Peak abundances of PET were 0.7–1.87 items/g at 2 hours, n=Not reported in abstract.
- Peak abundances of PVC were 0.55–1.5 items/g at 2 hours, n=Not reported in abstract.
- Peak abundances of PS were 2.92–6.63 items/g at days 4–5, n=Not reported in abstract.
- Superoxide dismutase (SOD) peaked at 87.3 U/mg on day 7, n=Not reported in abstract.
- Catalase (CAT) peaked at 62.5 U/mg on day 7, n=Not reported in abstract.
- Reduced glutathione (GSH) decreased to 3.2 µmol/g, n=Not reported in abstract.
Limitations
- Short-term exposure effects only.
- Small sample size not reported.
- Lack of long-term follow-up data.
- Single-species study limits generalizability.
- Potential confounding factors not controlled.