Microplastic in beach sediment from Mary’s Point, Shepody National Wildlife Area, southeastern New Brunswick

Abstract

Microplastic pollution has become an increasingly pervasive global contaminant, yet protected coastal environments remain insufficiently characterized. A baseline assessment is established here for microplastics within the beach sediments of Mary’s Point, a nationally and internationally protected site of high ecological significance in the upper Bay of Fundy. Fourteen sediment cores collected in 2022 and 2024 were analyzed using a five stage extraction protocol integrating sequential density separations with an oleophilic phase, enabling the recovery of a broad range of polymer densities. A total of 1,806 microplastic particles were identified, with secondary fibres (resulting from the degradation of larger plastic items) more than 90% of all particles. Mean abundances declined significantly from 990.8 microplastics per kilogram of sediment (MP/kg) in 2022 to 343.5 MP/kg in 2024, driven by episodic, high-energy storm reworking. While storm surges scoured upper sediment layers, the macroscopic sand matrix exhibited geomorphic resilience, showing no statistically significant temporal shift in median grain size. Lateral and vertical heterogeneity in microplastic distribution reflects dynamic sedimentary processes. Findings demonstrate that even remote, protected shorelines function as dynamic sinks for long range microplastic contamination modulated by episodic high energy events.