Microplastics (MPs) have been widely documented in marine biota, with a notable presence in bivalve species. This study examines microplastic (MP) contamination in oysters across a subtropical estuarine system, revealing widespread and highly variable levels of contamination. Our results indicate a general trend of higher contamination in areas with greater anthropogenic impact, and unexpectedly high values in remote Marine Protected Areas, suggesting alternative sources of MPs. We observed a 94.31 % frequency of occurrence and an average contamination level of 8.16 ± 6.39 MP.ind, 1.06 ± 1.28 MP.g, and 7.54 ± 6.55 MP.g. Transparent fibers, predominantly composed of polyester and polyethylene from likely textile origins, were the most common. The findings underscore the significance of MP pollution in marine environments, even in protected zones. For enhanced spatial assessment and consistent data comparison, we recommend that future studies include MP quantities in terms of dry weight (MP.g) and biometric data such as size and weight.

中文翻译：

---

牡蛎中的微塑料污染在亚热带河口系统中广泛但不均匀地发生

微塑料 (MP) 在海洋生物群中已被广泛记录，特别是在双壳类物种中明显存在。这项研究检查了亚热带河口系统牡蛎中的微塑料 (MP) 污染，揭示了广泛且高度可变的污染水平。我们的结果表明，人为影响较大的地区污染程度较高，而偏远海洋保护区的污染程度出人意料地高，这表明了 MP 的替代来源。我们观察到发生频率为 94.31%，平均污染水平为 8.16 ± 6.39 MP.ind、1.06 ± 1.28 MP.g 和 7.54 ± 6.55 MP.g。透明纤维是最常见的，主要由可能来自纺织品的聚酯和聚乙烯组成。研究结果强调了海洋环境中MP污染的重要性，甚至在保护区也是如此。为了增强空间评估和一致的数据比较，我们建议未来的研究包括以干重 (MP.g) 表示的 MP 数量以及尺寸和重量等生物特征数据。