Eutrophication ExacerbatesMicroplastic BioaccumulationRisks in Coastal Fish

Microplastic bioaccumulation (MPB) within marine fish through the food chain has been extensively validated in traditional experimental studies. However, the idealized conditions of these studies fail to fully capture the complex, nonlinear interactions among marine microplastics, biota, and environmental factors in real-world scenarios, and the spatiotemporal characteristics of risks are lacking in these studies, hindering the accurate assessment and control of risk. To address the above knowledge gaps, we constructed an improved sparrow search algorithm/geographic random forest (ISSA–GRF) conceptual framework and analyzed MPB in 82 common fish species from coastal ecosystems. The rate of MPB in coastal fish in 22 major marine ecosystems has increased by an average of 3.56% over the past decade. Hotspot areas such as the Red Sea coast, Gulf of Thailand coast, and Sulawesi Sea coast were identified; the bioaccumulation rates increased by 8.00%, 5.68%, and 5.34%, respectively. Ocean eutrophication, triggered by changes in nutrient levels, was revealed as the main driver via a causal analysis. These findings not only independently validate the increasing risk of microplastic biological accumulation outside the laboratory environment but also highlight the importance of controlling marine eutrophication to mitigate the biological risks associated with microplastics.