Hierarchical and cascading changes in the functional traits of soil animals induced by microplastics: A meta-analysis

Given the immense quantities of plastics in the environments worldwide, it is inevitable that soil animals are exposed to microplastics. However, a comprehensive elucidation of the cascading responses of different levels of functional traits in soil animals to microplastics remains unclear. A meta-analysis based on 80 published studies was conducted to quantify the hierarchical changes in soil animal traits from genes to survival under microplastics exposure. Soil animals substantially increased (by 62.1%) reactive oxygen species (ROS), copies of antioxidant genes increased by 35.7%, and antioxidant enzyme activities increased by 11.5% under the threat of microplastics. Unfortunately, the antioxidant responses did not completely eradicate the increased ROS. Animal traits at behavioral and survival levels were consequently significantly decreased (e.g., movement capacities, reproduction rate, growth rate, and survival rate decreased by 22.7%, 12.8%, 7.5%, and 3.1%, respectively). Microfauna endured more severe damage by microplastics due to higher ROS (63.7%) than macrofauna (33.5%). Additionally, round microplastics typically caused severe damage to soil animal survival rate that was inhibited by 16.6%. This study aimed to quantify the cascading responses of soil animal functional traits at multiple levels to microplastics, which will provide a comprehensive perspective for assessing the toxicities of microplastics in soil environments.