Polyethylene microplastics adhere to Lemna minor (L.), yet have no effects on plant growth or feeding by Gammarus duebeni (Lillj.)

Abstract

Microplastics (1-1000 μm) are ubiquitous in the marine, freshwater and terrestrial environments. These microsized plastics are considered freshwater pollutants of emerging concern, although the impacts on organisms and ecosystems are not yet clear. In particular, effects of microplastics on freshwater aquatic plants and the fate of microplastics in the freshwater trophic chain remain largely unexplored. Here we demonstrate that 10-45 μm polyethylene (PE) microplastics can strongly adsorb to all surfaces of the duckweed species Lemna minor. Despite adsorbance of up to 7 PE microplastics per mm², seven day exposure experiments showed that photosynthetic efficiency and plant growth are not affected by microplastics. Rather, dense surface coverage suggests L. minor as a potential vector for the trophic transfer of microplastics. Here we show that the freshwater amphipod Gammarus duebeni can ingest 10-45 μm PE microplastics by feeding on contaminated L. minor. In this study, ingestion of microplastics had no apparent impact on amphipod mortality or mobility after 24 or 48 h exposure. Yet, the feeding study showed that the fate of microplastics in the environment may be complex, involving both plant adsorbance and trophic transfer.

Keywords: Aquatic plants; Ecotoxicology; Freshwater; Freshwater macroinvertebrates; Microplastics; Polyethylene; Trophic transfer.