Microplastics (MPs) are currently one of the main problems of marine pollution, being found in all environmental matrices. Due to their size, they can be ingested by organisms directly (from the environment) or indirectly (with their prey). The objective of this study was to analyze the occurrence, abundance, concentration, and chemical nature of MPs present in the gastrointestinal tract of two fish species, Patagonotothen guntheri and Patagonotothen ramsayi, both of which are key in the food web of the Marine Protected Area Namuncurá/ Banco Burdwood (MPA N/BB). The analyzed species presented high values of MPs per individual (MPs/ind.) and occurrence compared to other studies. P. guntheri tended to have a lower number of MPs/ind. and occurrence than P. ramsayi (P. guntheri: 2.50 ± 1.93 MPs/ind., 82.50 %; P. ramsayi: 3.93 ± 2.91 MPs/ind., 90.60 %). While fibers were the predominant MPs in both species, P. ramsayi had a greater number of fragments and a greater variety of MPs chemical composition than P. guntheri. The prevailing chemical composition was cellulosic material (cellulose and cellulose mixed with polyamide and polyester). Synthetic fibers and fragments such as polyester (PET), alkyd resin, polyurethane, polyethylene, polyacrylic fiber and poly(ethylene-co-vinyl acetate-co-vinyl chloride) were also found. Although both species have a generalist diet, the differences found may be due to the fact that P. guntheri has benthopelagic feeding habits while P. ramsayi has demersal-benthic. Our study is the first report on the presence and characterization of MPs in organisms relevant to food webs in the Southwest Atlantic.

微塑料（MP）是目前海洋污染的主要问题之一，存在于所有环境基质中。由于它们的大小，它们可以被生物体直接（从环境中）或间接（通过猎物）摄入。本研究的目的是分析两种鱼类（ Patagonotothen Guntheri和Patagononotothen ramsayi）胃肠道中 MP 的出现、丰度、浓度和化学性质，这两种鱼类都是海洋保护区食物网的关键。 Namuncurá/Banco Burdwood (MPA N/BB)。与其他研究相比，所分析的物种呈现出较高的个体 MP 值（MP/ind.）和发生率。P. Guntheri的 MPs/ind 数量往往较少。和发生率高于P. ramsayi ( P. Guntheri: 2.50 ± 1.93 MPs/ind., 82.50 %; P. ramsayi: 3.93 ± 2.91 MPs/ind., 90.60 %)。虽然纤维是这两个物种的主要 MP，但P. ramsayi比P. Guntheri具有更多的碎片和更多种类的 MP 化学成分。主要的化学成分是纤维素材料（纤维素以及与聚酰胺和聚酯混合的纤维素）。还发现了合成纤维和碎片，例如聚酯（PET）、醇酸树脂、聚氨酯、聚乙烯、聚丙烯酸纤维和聚（乙烯-醋酸乙烯酯-共聚氯乙烯）。尽管这两个物种都有通用饮食，但发现的差异可能是由于P. Guntheri具有底栖食性，而P. ramsayi具有底栖性。我们的研究是关于西南大西洋食物网相关生物体中 MP 的存在和特征的第一份报告。