Bioaccumulation and Trophic Transfer of Microplastics in Aquatic Invertebrates: A Trait-Habitat-Particle (THP) Framework

Microplastic pollution has emerged as a pervasive stressor in aquatic ecosystems, with aquatic invertebrates playing central roles in particle uptake, retention, and transfer within food webs. This review synthesises evidence on microplastic ingestion, bioaccumulation, trophic transfer, and biomagnification across major aquatic invertebrate groups, including arthropods, molluscs, sediment-associated worms, suspension feeders, and echinoderms. A structured literature search identified 66 studies spanning freshwater, estuarine, and marine environments. Evidence indicates that microplastic uptake occurs through multiple pathways, including filter feeding, deposit feeding, grazing, and predator–prey interactions. Across the reviewed studies, feeding strategy, habitat-specific exposure, and particle characteristics were recurrently associated with variation in microplastic ingestion, retention, and trophic transfer. While ingestion and bioaccumulation were widely documented, quantitative understanding of trophic transfer within aquatic invertebrate food webs remained limited, and no conclusive evidence of biomagnification was identified. To interpret recurring patterns, this review proposes the Trait–Habitat–Particle (THP) framework as a conceptual tool linking biological and functional traits, habitat-mediated exposure, and particle properties. Methodological inconsistencies, limited representation of certain taxa and habitats, and insufficient quantification of trophic transfer remain important knowledge gaps. Future research should prioritise methodological standardisation and ecologically realistic long-term studies.