Climate warming will alter the impact of microplastics on the bioavailability of arsenic in a subtropical estuary

The coupling of climate warming and microplastics may affect the dynamics of arsenic bioavailability in estuarine sediments, but the specific processes and regulatory mechanisms of this phenomenon remain poorly investigated. In this study, a typical subtropical estuary - Min River estuary was selected to explore the dynamics pattern, composition characteristics and regulatory mechanism of arsenic bioavailability in sediments under the coupled influence of climate warming and microplastics (type and dose) through incubation experiments by utilizing DGT techniques. The results showed that the high-dose PLA-MPs significantly enhanced the arsenic bioavailability after warming, while low-dose PET-MPs inhibited the effect. High-dose PET-MPs and low-dose PLA-MPs significantly promoted the oxidation of arsenic (III) after warming, while low-dose PET-MPs and high-dose PLA-MPs inhibited the effect. The interaction of temperature, type and dose of MPs significantly affected arsenic bioavailability. The abundances of Bacteroidota decreased, while the abundances of Chloroflexi and Desulfobacterota increased significantly after warming. The correlation between microorganisms and the bio-As was decreased by warming. These findings provide valuable insight for understanding the complex interplay of climate warming and MPs on As-contaminated estuary.