In the coastal environment, a large amount of microplastics (MPs) can accumulate in the sediments of seagrass beds. However, the potential impact these pollutants have on seagrasses and associated organisms is currently unknown. In this study, we investigated the differences in MPs abundance and composition (i.e., shape, colour and polymer type) in marine sediments collected at different depths (−5 m, −15 m, −20 m) at two sites characterized by the presence of meadows and at one unvegetated site. In the vegetated sites, sediment samples were collected respectively above and below the upper and lower limits of the meadow (−5 m and −20 m), out of the meadow, and in the central portion of the meadow (−15 m). By focusing on the central part of the meadow, we investigated if the structural features (i.e. shoots density and leaf surface) can affect the amount of MPs retained within the underlying sediment and if these, in turn, can affect the associated benthic communities. Results showed that the number of MPs retained by meadows was higher than that found at the unvegetated site showing also a different composition. In particular, at vegetated sites, we observed that MPs particles were more abundant within the meadow (at – 15 m), compared to the other depths, on unvegetated sediment, with a dominance of transparent fragments of polypropylene (PP). We observed that MPs entrapment by was accentuated by the higher shoots density, while the seagrass leaf surface did not appear to have any effect. Both the abundance and richness of macrofauna associated with rhizomes appear to be negatively influenced by the MPs abundance in the sediment. Overall, this study increases knowledge of the potential risks of MPs accumulation in important coastal habitats such as the meadows.

中文翻译：

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Posidonia oceanica 草甸保留微塑料的能力及其对相关大型底栖动物群落的影响

在沿海环境中，海草床的沉积物中会积聚大量微塑料（MP）。然而，这些污染物对海草和相关生物的潜在影响目前尚不清楚。在本研究中，我们研究了在两个以存在为特征的地点不同深度（−5 m、−15 m、−20 m）收集的海洋沉积物中 MP 丰度和组成（即形状、颜色和聚合物类型）的差异。草地和一个没有植被的地方。在植被场地，分别在草甸上下限（-5 m和-20 m）上方、下方、草甸外、草甸中部（-15 m）采集沉积物样品。通过关注草地的中心部分，我们研究了结构特征（即芽密度和叶表面）是否会影响底层沉积物中保留的 MP 数量，以及这些是否反过来会影响相关的底栖群落。结果表明，草地保留的 MP 数量高于未植被地点的 MP 数量，也显示出不同的组成。特别是，在植被覆盖的地点，我们观察到，与其他深度、无植被沉积物相比，草地（15 m 处）内的 MP 颗粒更为丰富，且以透明的聚丙烯 (PP) 碎片为主。我们观察到，较高的枝条密度加剧了 MP 的截留，而海草叶表面似乎没有任何影响。与根茎相关的大型动物的丰度和丰富度似乎都受到沉积物中 MPs 丰度的负面影响。总体而言，这项研究增加了人们对草地等重要沿海栖息地 MP 积累潜在风险的了解。