Fibrous Microplastics as an Independent Risk Factor: Bioaccumulation, Gut– Liver Translocation, and Trophic Biomagnification in Marine Food WebsMarine Trophic Chains

Abstract

Fibrous microplastics dominate marine debris yet remain understudied compared with spherical and fragmented forms. Their high aspect ratio (10–50) confers unique mechanical flexibility and surface reactivity. In controlled exposure experiments (10–1,000 μg L⁻¹; 7–60 days), fish and bivalves retained fibers in intestinal villi with a bioaccumulation factor of 3.8 ± 0.4, three to four times higher than other morphologies. Micro-FTIR imaging tracked fibers crossing the intestinal epithelium and localizing in hepatic lobules, indicating a novel “gut–liver” pathway. At environmentally relevant concentrations (10 μg L⁻¹, 60 days), fibers disrupted eight energy metabolism pathways, doubled superoxide dismutase activity, and tripled tumor necrosis factor-α expression, suggesting chronic metabolic and inflammatory stress. In a threelevel food web experiment (algae → shrimp → fish), fibers exhibited significant biomagnification (BMF = 1.75 ± 0.12), unlike spheres or fragments (BMF < 1.0). These findings demonstrate that morphology is an independent determinant of microplastic risk, beyond size and concentration.