The presence of plastic cosmetic microbeads in the environment due to their extensive use in society and inevitable dispersal into wastewater is concerning. Therefore, it is vital to understand the processes of microplastic uptake and elimination by aquatic organisms, and to further assess their potential to cause harmful effects and wider impacts. We therefore investigated the short-term (48-h) and long-term (21-d) uptake, elimination, and effects of exposure to polyethylene microbeads (a mixture of fragments and spheres extracted from commercially available facial scrubs) on the freshwater snail, Biomphalaria glabrata. We found fast uptake in the short-term (75 μg/g/h) and the long-term (6.94 μg/g/h) in B. glabrata exposed to 800 particles/200-mL and 80 particles/200-mL, respectively. Irregular fragments were more easily ingested and egested compared to spheres (ANOVA, p < 0.05) in both 48-h and 21-d exposures. The mean size of the fragments in B. glabrata tissues (413 ± 16 μm) after 48-h exposure was significantly larger than that of the standard sample (369 ± 26 μm) (ANOVA, F_3,20 = 3.339, p = 0.033), suggesting that aggregation in the gut may occur. Floating feces containing microbeads were observed in the long-term exposure, which could alter the fate, behavior, and bioavailability of egested microbeads. No significant effects on survival and growth were shown within 48-h or 21-d exposure periods. Thus, further studies on the specific features of microplastics (e.g., their shape and size) influencing uptake and elimination, as well as toxic molecular mechanisms, should be explored in future ecotoxicological studies.

Heavy metal (HM) pollution in the marine environment has been of concern for decades. The potential impact of HMs carried by emerging marine pollutants such as microplastics (MPs) has attracted attention only in recent years. In this study, we investigated the single and combined chronic toxic effects (growth, burrowing behavior, and histopathology) of cadmium (Cd, three concentrations of low, medium, and high) and polystyrene (PS) microspheres (1 μm, 10 μg/L) on the coastal polychaete Perinereis aibuhitensis. Cd bioaccumulation under two exposure scenarios was also explored. Our results showed that Cd and PS did not affect worm growth for single or combined exposure, while 13.08 μg/L of Cd (Cd_L) alone significantly decreased the burrowing time of P. aibuhitensis in sediment. The presence of PS mitigated the hormetic effect of Cd on worm burrowing behavior, and this influence was Cd concentration-related. Cd body burdens in worms exposed to the medium and high Cd concentrations (Cd_M and Cd_H) were significantly greater than those of control worms with or without the presence of PS. In addition, Cd bioaccumulation was significantly higher with the coexistence of PS than those of Cd alone at the Cd_L and Cd_M groups. Histopathological analyses demonstrated a trend of epidermal and intestinal damages for single Cd/PS and their combined groups, and the contribution of PS-MPs should not be ignored. Our results indicate that the toxic effects and bioaccumulation pattern of Cd could be altered with the presence of PS-MPs for P. aibuhitensis, especially at environmentally relevant concentrations.