Global Coastal Hotspots and the Cascading Effect of Microplastic Burden in Marine Fish

Microplastic burdens in marine fish exhibit a nonlinear relationship with environmental concentrations, yet current global-scale biological risk assessments suffer from systematic biases. We compiled a comprehensive dataset of microplastic burdens across 495 marine fish species from coastal regions worldwide, comprising 4,154 in situ measurements. By implementing an interpretable machine learning framework, we identified distinct spatiotemporal hotspot clustering patterns in fish microplastic burdens. Fish from the Sulu-Celebes Sea, Southeast Australian Shelf, and Hudson Bay exhibited microplastic burdens that were 74.14%, 56.28%, and 41.58% above the global mean, respectively. Globally, microplastic burdens (<5 mm) increased by 2.25% between 2010 and 2023, whereas the number of submillimeter particles (<0.1 mm) increased by 17.47% during this period. This divergence underscores potential microplastic biological risks under continuous environmental and biological degradation or transformation conditions. Cascading ecological and anthropogenic processes collectively regulate fish microplastic burdens. Mediterranean fish showed 25.39% higher microplastic burdens in summer when chlorophyll concentrations were lower, whereas East Asian waters with biodiversity buffering exhibited 37.37% lower burdens in summer. This study provides a critical reevaluation of the empirical foundation for assessing microplastic biological risks in coastal ecosystems.