Interactions between microplastics and soil fauna: A critical review

Microplastics (MPs) are emerging contaminants that cause diverse impacts on soil ecosystems. As integral members of soil food webs, soil fauna exert key ecological functions such as litter decomposition, nutrient cycling, and energy flow. MPs may damage soil fauna and their ecological functions, posing ecological and health risks. Meanwhile, soil fauna can act on MPs. Hereby, we aim to summarize the interactions between MPs and soil fauna. This article first introduces the source, occurrence and characteristics of MPs in soils, and then highlights the interactions between MPs and soil fauna, particularly earthworms and nematodes. MPs can cause negative impacts on the growth, reproduction, lifespan, and survival of soil fauna, via diverse toxicity mechanisms such as ingestion and bioaccumulation, histopathological damage, oxidative stress, DNA damage, genotoxicity, reproductive toxicity, neurotoxicity, metabolic disorders, and gut microbiota dysbiosis. MPs can also interact with other contaminants to produce combined toxicity to soil fauna. In turn, soil fauna can contribute to the formation and breakdown of MPs, alter the migration of MPs in soil, and even transfer accumulated MPs to higher trophic levels. Finally, given the large knowledge gap regarding the interaction of soil fauna and MPs, several future research priorities are recommended.