Uptake, accumulation and associated cellular alterations of environmental samples of microplastics in the seaworm Hediste diversicolor

The ubiquitous distribution of microplastics (MPs) in the marine environment raises global concern to understand their impact. Environmental MPs have been shown to exhibit different physicochemical properties during their life cycles. However, the body of knowledge regarding their accumulation and biological effects is still significantly limited compared to manufactured MPs. To evaluate the hazardous effects of a mixture of environmental MPs collected along the Tunisian beaches, their accumulation and cellular effects were investigated in Hediste diversicolor. MP sample was composed of polyethylene (PE), polyethylene vinyl acetate (PEVA), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and polyamide (PA) analyzed using Raman microspectroscopy (RM). The concentrations of MPs in seaworm tissues increased over time, following the order 1.2-0.45 µm > 3-1.2 µm > 100-3 µm. The ingestion of MPs by H. diversicolor reduced their survival and growth, affected the neuro-transmission and antioxidant pathways. Our data emphasised that the toxic effects of environmental MPs were closely related to the exposure dose and period. The results also demonstrated that the size distribution of MPs in seaworms was mainly correlated with biochemical markers. This study highlights the ecological risk in the ingestion and accumulation of environmental MPs by biota that threatens their functional parameters.