Tracking radiolabelled polystyrene microplastics in young Atlantic scallop (Placopecten magellanicus): bioaccumulation, depuration and bioenergetic impacts assessment

The massive production and use of plastics have resulted in their release, under various forms, in marine ecosystems, now a major environmental pollution concern. Degradation and fragmentation processes break down plastics into fine particles, called microplastics (MPs) and nanoplastics (NPs), whose bioaccumulation and effects on marine organisms remain largely unknown. This study investigates the long-term bioaccumulation and depuration kinetics as well as the biodistribution of 1.5 ± 0.3 μm polystyrene microparticles (PS-MPs) and assesses their impact on the energy reserves of young non-reproductive Atlantic scallops (Placopecten magellanicus). Three treatments were used during a three-month exposure period; organisms fed with a mixture of microalgae and ¹⁴C-labelled PS (¹⁴C-PS-MPs) at concentrations close to those expected in the marine environment; organisms on the same treatment but with non-radiolabelled PS-MPs, and control organisms fed only a mixture of microalgae. Thereafter, depuration was monitored over 3 months, scallops receiving only microalgae. Autoradiographic data showed that ¹⁴C-PS-MPs ingested by scallops were concentrated in the digestive tract. ¹⁴C-PS-MPs levels measured in samples of hepatopancreas (6300 ± 4900 Bq•g^-1_ww) and muscle (85 ± 81 Bq•g^-1_ww) exhibited large interindividual variability and no temporal trend during exposure. Upon depuration, 91 % of ¹⁴C-PS-MPs in scallops was eliminated in less than 0.65 d and little radioactivity remained in hepatopancreas and muscle after 7 d (<200 and < 20 Bq•g^-1_ww, respectively). Finally, the consumption of non-labelled PS-MPs had no detectable impact on the energy reserves of scallops such as lipid and glycogen concentrations.