Efficacy of microplastic depuration on two commercial oyster species from the west coast of Ireland

Studies investigating microplastics (MPs) in marine species have been published over recent decades, including studies on depuration efficacy on aquaculture products. This preliminary study investigates the depuration efficacy of MPs in two commercial oyster species from Ireland. The innovative aspects are the sampling size (n = 50 per species) and the experiment duration (up to 96 h). The case study organisms are the Pacific oyster (Magallana gigas) and the European flat oyster (Ostrea edulis). Prior to depuration, the mean MP concentration on M. gigas edible tissue was 0.6 MP g⁻¹ while for O. edulis was 0.4 MP g⁻¹. Significant differences in mean MP concentrations were identified after 96-h for M. gigas 0.2 MP g⁻¹ (p = 0.014) and O. edulis, 0.1 MP g⁻¹ (p = 0.003). Additionally, no significant correlation was established between MP concentrations and edible tissue weight. Polymer identification revealed that 51.6% were fibers of natural origin. Preliminary results show that increasing depuration times beyond 72-h can significantly reduce MPs in selected oyster species, which is what is being recommended with this baseline study. Further investigation on commercial conditions at adequate depuration facilities is required. Given the relevance of low-trophic aquaculture species for local economies, this preliminary study provides important baseline information for stakeholders.