Abstract
As the world’s largest archipelagic state, Indonesia is increasingly exposed to microplastic contamination across its aquatic environments. This review synthesizes evidence from 497 publications reporting microplastic occurrence in environmental matrices across the Indonesian archipelago, including freshwater and marine waters, sediments, and aquatic biota. The analysis examines reported abundance levels, dominant polymer types, spatial patterns of contamination, and methodological approaches used in microplastic research conducted in Indonesia. The literature reveals a pronounced geographic imbalance in research coverage. More than 60% of studies were conducted in western Indonesia, with a strong concentration on Java Island, whereas large parts of eastern Indonesia remain poorly documented. Reported concentrations vary widely among environmental matrices and sampling designs, reflecting differences in both environmental conditions and analytical practices. Notably, studies that did not apply rigorous quality assurance procedures or confirm polymer composition using spectroscopic techniques tended to report markedly higher concentrations, suggesting that methodological limitations may contribute to inflated contamination estimates. To place these observations into a comparable framework, risk band thresholds were derived from the abundance dataset using a quantile-based statistical approach. Overall, this review provides an integrated baseline of microplastic contamination across Indonesian environments and identifies critical geographic and methodological gaps that should guide future monitoring strategies and environmental risk assessments.