Multiple species ingest microplastic but few reflect sediment and water pollution on sandy beaches: A baseline for biomonitoring

Databases recording the ingestion of microplastics by marine animals are growing. This is also recurrent on sandy beaches, where different biomonitors have been proposed to monitor the impacts of plastic pollution. We aimed to record the occurrence of suspected microplastic (SMP) in the digestive tract of multiple taxa (n = 45 identified species) and test whether some macroinvertebrates and fishes ingested SMPs proportionally with the pollution level of sediment and water; thus, we aimed to depict which sandy beach species could be used as biomonitors. Among all taxa, 10 macroinvertebrates and 12 fish species were reported to ingest SMP for the first time. SMP morphotypes proportion differed between abiotic and biotic compartments. Moreover, 10 of 12 taxa did not have SMP concentration linearly related with SMP in sediment and water. Our findings suggest that few species from sandy beaches can be used as efficient biomonitors, although almost all ingest plastic polymers.

Automated summary

Databases on microplastic ingestion by marine animals are increasing, including on sandy beaches where biomonitors are proposed to monitor plastic pollution. This study aimed to document suspected microplastic occurrence in the digestive tract of multiple taxa and determine if certain invertebrates and fish ingested microplastics in proportion to sediment and water pollution levels, hence identifying potential sandy beach biomonitors. Among 45 species examined, 10 macroinvertebrates and 12 fish species were found to ingest microplastics for the first time. Microplastic morphotypes differed between abiotic and biotic compartments. Furthermore, 10 out of 12 taxa did not show a linear relationship between microplastic concentration and sediment and water microplastic levels. Our findings indicate that only a few species from sandy beaches can be efficient biomonitors, despite widespread plastic ingestion.