Multi-diversity dominates the response of ecosystem multifunctionality and stability to biogeochemical materials that exceed planetary boundaries

Microplastic contamination and nutrient deposition have exceeded planetary boundaries, posing significant long-term risks to coastal saline-alkali wetland ecosystems. While most studies focus on the effects of individual stressors, such as microplastics or nutrients, the combined impacts of multiple stressors remain underexplored. In this study, we examined the effects of the microplastome-comprising various microplastics and their associated substances-along with nutrient deposition on plant communities, ecological efficiency, ecosystem multifunctionality, and stability in coastal wetlands. Our results demonstrate that interactions between the microplastome and nitrogen (N) deposition significantly enhance ecosystem multifunctionality. Furthermore, elevated microplastic contamination combined with N deposition improved ecosystem stability and increased plant community sensitivity to stressors. These changes were primarily driven by increased biodiversity and complementary interactions within the community. Random forest analysis and structural equation modeling revealed that the cascading effects of microplastic pollution and nutrient deposition-particularly on soil nutrients, fertility, and enzyme activities-were pivotal in driving shifts in ecosystem multifunctionality and stability. This study advances our understanding of the integrated impacts of biodiversity and multiple anthropogenic stressors, underscoring their role in shaping the multifunctionality and stability of coastal saline-alkali wetland ecosystems.