An Initial Assessment of Microplastic Distribution across Trophic Levels in Benthic Ecosystems of Tidal Flats

Abstract

Microplastics (MPs) are widespread pollutants, yet their distribution across the trophic levels in tidal flat ecosystems remain poorly understood. We investigated MPs in sediments, seawater, macroalgae, and benthic organisms (19 species, 81 individuals) from two tidal flats in Incheon, Republic of Korea using a count-based approach. MPs were dominated by polypropylene, polyethylene, and polystyrene, with 20–100 μm particles accounting for 65% of total particles. Abundance ranged from 0.85 to 2.72 MPs/g dw in sediments and 0.4–2.2 MPs/L in seawater. Predators (3.63 ± 1.44 MPs/g) contained higher MP levels than their prey, filter feeders (0.87 ± 0.63 MPs/g), while detritivores (26.69 ± 31.45 MPs/g) exhibited higher abundances than macroalgae (11.62 ± 8.37 MPs/g). Deposit feeders accumulated significantly more MPs than filter feeders, reflecting feeding strategy-dependent exposure pathways. Bioconcentration factors (BCF > 1), bioaccumulation factors (BAF > 1), and predator-prey biomagnification factors ranging from 3.9 to 9.6 were observed based on particle counts. Despite lower MP abundance, filter feeders exhibited higher potential polymer-associated hazards, suggesting that MP abundance alone does not fully represent ecological risk. These findings highlight the importance of feeding ecology in shaping MP exposure and accumulation in tidal flats.