Microplastics in small Island ecosystems: Integrating evidence on distribution, bioaccumulation, and social-ecological impacts

Background: Small island ecosystems are highly vulnerable to marine plastic pollution due to geographic isolation, limited waste-management capacity, and exposure to converging ocean currents. Yet, integrated syntheses linking contamination patterns with ecological and socio-economic impacts remain scarce. Methods: A structured literature review of peer-reviewed studies published between January 2020 and August 2025 was conducted using the Scopus database and targeted reference screening. Empirical studies measuring microplastics in island or near-island environments and addressing trophic transfer or socio-economic impacts were prioritized, while methodological differences were considered qualitatively in interpreting evidence strength. Findings: Sediments consistently act as long-term sinks in island systems, often exhibiting orders-of-magnitude higher microplastic concentrations than concurrent water samples. Fragments and fibres dominate particle morphologies, with polyethylene, polypropylene, and polystyrene the most common polymers. Microplastics are ingested across trophic levels, but evidence for systematic trophic biomagnification remains mixed. Sublethal effects and contaminant or pathogen transfer reduce ecosystem productivity and fisheries performance, while socio-economic impacts include declining seafood quality and disproportionate burdens on vulnerable island communities. Conclusion: Microplastic pollution in small islands presents coupled ecological and social risks that remain understudied and are constrained by methodological heterogeneity. Priority actions include standardized sampling/analysis protocols, long-term monitoring, realistic exposure experiments, and targeted mitigation (waste management upgrades, community-based interventions). Novelty/Originality of this article: This is the first structured synthesis (2020–2025) explicitly integrating occurrence, trophic-level bioaccumulation, and socio-ecological impacts of microplastics in small-island ecosystems, highlighting evidence gaps and policy-relevant research priorities.