Microplastics in bivalves have caused widespread concern due to their potential health risk to humans. In this study, microplastics in the digestive systems of four locally cultured bivalve species (scallop Chlamys farreri, mussel Mytilus galloprovincialis, oyster Crassostrea gigas, and clam Ruditapes philippinarum) in Qingdao, China, were analyzed and detected in 233 out of 290 bivalve samples (80%) over four seasons. The microplastic abundance in four species of bivalves ranged between 0.5 and 3.3 items/individual or 0.3 and 20.1 items/g wet weight digestive system, with significant species-specific and region-specific differences but no season-specific differences. Microfiber was the most predominant shape of all microplastics found. Eighteen types of polymer with diameters between 7 and 5000 μm were identified by μ-FT-IR (505 of 587 suspected items identified as microplastics) with polyvinyl chloride (PVC) and rayon being the most abundant ones. Bivalves collected in summer contained more larger-sized microplastics. R. philippinarum accumulated more smaller-sized microplastics and showed different microplastic features compared with the other three species of bivalves. By comparing and analyzing the microplastic polymer types between each bivalve species and the ambient environment, microplastic in clam can best reflect the variability of microplastic polymer types in sediment among different areas. Mussels can reflect the variability of microplastic polymer types in water to an extent. Therefore, clam and mussel are recommended to serve as bioindicators for microplastic pollution in the sediment and water, respectively. The occurrence of microplastics pollution in bivalves worldwide is wide, and bivalves can act as the transporter of microplastics to humans. Our results suggest that bivalves have an important role as environmental bioindicators and the pollution of microplastics in bivalves needs attention.

双壳类动物中的微塑料由于其对人类的潜在健康风险而引起了广泛关注。在这项研究中，四种本地双壳类物种（扇贝的蛤类，贻贝的Mytilus galloprovincialis，牡蛎的Crassostrea gigas和蛤的Ruditapes philippinarum）的消化系统中的微塑料。在四个季节中，对290个双壳类动物样本中的233个（占80％）进行了分析和检测。四种双壳类动物的微塑性丰度介于0.5至3.3个/克或0.3至20.1个/克的湿重消化系统之间，具有明显的物种特异性和区域特异性差异，但没有季节特异性差异。在所有发现的微塑料中，超细纤维是最主要的形状。通过μ-FT-IR（587个可疑物品中的505个被确定为微塑料）鉴定出了18种类型的直径在7至5000μm之间的聚合物，其中聚氯乙烯（PVC）和人造丝最为丰富。在夏季收集的双壳类动物含有更多的较大尺寸的微塑料。菲律宾河豚与其他三种双壳类动物相比，它们积累了更多的较小尺寸的微塑料，并表现出不同的微塑料特征。通过比较和分析每种双壳类动物与周围环境之间的微塑性聚合物类型，蛤中的微塑性可以最好地反映不同地区沉积物中微塑性聚合物类型的变异性。贻贝可在一定程度上反映水中微塑性聚合物类型的变异性。因此，建议将蛤和贻贝分别用作沉积物和水中微塑性污染的生物指示剂。在全世界的双壳类动物中，微塑料污染的发生范围很广，双壳类动物可以充当微塑料向人类的转运者。