Synthetic microfibers have been reported in most aquatic environments and represent a large proportion of environmental microplastics. However, they remain largely under-represented in microplastic ecotoxicity studies. The present study aims to investigate particle interaction with, and retention time in, aquatic organisms comparing microfibers, and microbeads. We used brine shrimp (Artemia sp.) and fish (Gasterosteus aculeatus) as invertebrate and vertebrate models, respectively. Organisms were exposed to a mixture of microbeads (polyethylene, 27–32 μm) and microfibers (dope dyed polyester; 500 μm-long) for 2 h, at high concentrations (100,000 part./L) in order to maximize organism-particles interaction. Artemia were exposed in the presence or absence of food. Fish were exposed either via the trophic route or directly via water, and water exposures were performed either in freshwater or seawater. In the absence of food, Artemia ingested high numbers of microbeads, retained in their digestive tract for up to 96 h. Microfiber ingestion was very limited, and its egestion was fast. In the presence of food, no microfiber was ingested, microbead ingestion was limited, and egestion was fast (48 h). Limited particle ingestion was observed in fish exposed via water, and particle retention time in gut did not exceed 48 h, both for direct and trophic exposure. However, water exposures resulted in a higher number of particles present in gills, and average retention time was higher in gills, compared to gut. This suggests that gills are organs susceptible to microplastic exposure and should be taken into account in fish exposure and effect studies. Our results show that particle ingestion and retention by organisms differ between microbeads and microfibers, suggesting particle selection based on size, shape, and/or color and species-specific selective feeding. We also showed that the presence of food results in limited particle ingestion and retention in Artemia and that microbeads are more likely to be transferred to organisms from upper trophic levels than microfibers. Finally, fish exposure to particles was not significantly different between freshwater and seawater conditions.

中文翻译：

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不同暴露情景下模型水生物种中合成超细纤维和微珠的暴露和保留时间

合成微纤维已在大多数水生环境中得到报道，并且在环境微塑料中占很大比例。然而，它们在微塑料生态毒性研究中的代表性仍然不足。本研究旨在通过比较微纤维和微珠来研究粒子与水生生物的相互作用和保留时间。我们分别使用丰年虾 (Artemia sp.) 和鱼 (Gasterosteus aculeatus) 作为无脊椎动物和脊椎动物模型。将生物体暴露于高浓度（100,000 份/升）的微珠（聚乙烯，27-32 微米）和微纤维（原液染色聚酯；500 微米长）的混合物中 2 小时，以最大限度地提高生物体与颗粒的相互作用. 在有或没有食物的情况下暴露卤虫。鱼类通过营养途径或直接通过水暴露，和水暴露在淡水或海水中进行。在没有食物的情况下，卤虫会摄入大量微珠，并在消化道中保留长达 96 小时。超细纤维的摄取非常有限，并且摄取速度很快。在食物存在的情况下，没有摄入微纤维，微珠摄入有限，并且摄入快（48小时）。在通过水暴露的鱼中观察到有限的颗粒摄入，并且颗粒在肠道中的保留时间不超过 48 小时，无论是直接暴露还是营养暴露。然而，与肠道相比，水暴露导致鳃中存在更多数量的颗粒，并且鳃中的平均保留时间更长。这表明鳃是易受微塑料暴露影响的器官，应在鱼类暴露和影响研究中加以考虑。我们的结果表明，微珠和微纤维之间生物体对颗粒的摄取和保留不同，这表明颗粒选择基于大小、形状和/或颜色以及特定物种的选择性喂养。我们还表明，食物的存在会导致卤虫中有限的颗粒摄入和滞留，并且与微纤维相比，微珠更有可能从上层营养级转移到生物体中。最后，在淡水和海水条件下，鱼类接触颗粒物的情况没有显着差异。我们还表明，食物的存在会导致卤虫中有限的颗粒摄入和滞留，并且与微纤维相比，微珠更有可能从上层营养级转移到生物体中。最后，在淡水和海水条件下，鱼类接触颗粒物的情况没有显着差异。我们还表明，食物的存在会导致卤虫中有限的颗粒摄入和滞留，并且与微纤维相比，微珠更有可能从上层营养级转移到生物体中。最后，在淡水和海水条件下，鱼类接触颗粒物的情况没有显着差异。