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The world is your oyster: low-dose, long-term microplastic exposure of juvenile oysters
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Juvenile oysters were exposed to polystyrene microbeads at three concentrations for 80 days to test long-term, low-dose effects, with microbeads detected in the intestines of exposed oysters but no significant impacts on growth, body condition, or lysosomal stability. The study suggests oysters can tolerate chronic low-level microplastic exposure without major physiological harm.
Bivalve filter feeders, such as oysters, filter large volumes of water and are particularly exposed to microplastics (MP). Consequently, these animals digest and assimilate high levels of MP in their bodies that may likely impact their physiology, and potentially affect shellfish stocks, benthic habitats and, indirectly, the health status of the marine ecosystem and human consumers. In this study we exposed juvenile oysters, to 3 different MP concentrations (10, 10 and 10 particles L), represented by 6μm Polystyrene (PS) microbeads, compared to a control treatment receiving no MP. The study ran for a period of 80 days to test for the impacts of MP on growth, Condition Index and Lysosomal Stability. From histological analysis, microbeads were detected in the intestines of exposed oysters and in the digestive tubules, but no cellular inflammatory features were observed over time. Weight and shell length remained comparable between the different treatments and control. We found that Condition Index in the highest concentration increased initially but significantly reduced over time. The oysters in the highest MP exposure also showed the lowest mean Lysosomal Stability score throughout the experiment. Lysosomes play a vital role in the cells defense mechanisms and breakdown of constituents, crucial for the oysters' wellbeing. Most importantly, we detected an increased mortality in those oysters who were chronically exposed to the highest loads of MP.
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Tissue-specific accumulation and integrated toxicological responses of the Pacific oyster, Crassostrea gigas, to chronic polyethylene microplastic exposure: An empirical toxicokinetic interpretation
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Scientists found that oysters exposed to microplastics for weeks build up the most plastic in their digestive glands, and this buildup was linked to stress hormones, liver-related enzymes, and immune changes. Since oysters are widely eaten, this suggests microplastic pollution could affect the health and safety of seafood, though more research is needed to know what this means for humans.
Experimental ingestion of fluorescent microplastics by pacific oysters, Crassostrea gigas, and their effects on the behaviour and development at early stages
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Pacific oyster embryos exposed to polystyrene microbeads showed increased developmental malformations at concentrations above 1 milligram per liter, and 3-day-old larvae exposed briefly to the same concentrations ingested particles in their digestive tract and showed reduced swimming speeds. The study highlights early larval stages as particularly sensitive windows for microplastic-induced developmental disruption.
Realistic environmental exposure to microplastics does not induce biological effects in the Pacific oyster Crassostrea gigas
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Pacific oysters were exposed to environmentally relevant concentrations of polyethylene and polypropylene fragments for 10 days followed by depuration, with microplastics detected in tissues but no significant effects on clearance rate, tissue integrity, antioxidant defense, or DNA damage. The results suggest that realistic environmental concentrations of these larger fragments may not cause measurable biological harm to oysters.
Do Environmentally Relevant Concentrations of Microplastics Pose a Threat to the Eastern Oyster, Crassostrea Virginica?
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This study exposed eastern oysters to polyester microfibers at environmentally realistic concentrations for 45 days, finding that even low doses affected their physiology including feeding, growth, and energy use. The results suggest that ecologically relevant microplastic levels may pose a threat to commercially important filter-feeding shellfish.
Do Polystyrene Beads Contribute to Accumulation of Methylmercury in Oysters?
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Researchers studied whether polystyrene microplastic beads contribute to methylmercury bioaccumulation in oysters (Crassostrea gigas), examining the sorption of methylmercury onto plastic beads and evaluating whether ingestion of contaminated beads elevated mercury levels in oyster tissue.
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