Early evidence of microplastics on seagrass and macroalgae

Microplastic accumulation on marine macrophytes, such as macroalgae and seagrasses, is a potentially critical but overlooked pathway by which microplastics enter the marine food web. Despite the possible significance of this pathway, few studies have examined the presence of microplastics on macrophytes found in situ. We quantified the density of microplastics found on the surfaces of three species of intertidal seagrasses (Cymodocea rotundata, Cymodocea serrulata and Thalassia hemprichii) and two species of subtidal macroalgae (Padina sp. and Sargassum ilicifolium), and found significantly higher microplastic densities on seagrasses than on macroalgae. However, we found no relationships between microplastic density and epibiont cover in either seagrass or macroalgae. Our study has provided early evidence of microplastics on macrophyte surfaces in situ, being the first such evidence for macroalgae, and the second for seagrasses.