Toxicity of polyethylene microplastics and atrazine to microorganisms in soil and gut of earthworms

Abstract

Nowadays, microplastics (MPs) extensively exist in soil environment, atrazine is an extensively utilized herbicide which residues accumulate in soil. The harmful effects of atrazine on earthworms are well investigated, however, the toxicity of co-exposure of MPs and atrazine to bacterial community in soil and gut of earthworms was unclear. Herein, the changes of bacterial communities in the soil and the gut of earthworms exposed to binary pollutants (MPs and atrazine) were investigated. The results showed that atrazine increased relative abundance of some soil indigenous atrazine-degrading bacteria (Pseudomonas, Flavobacterium) and gut-colonizing bacteria (Algoriphagus, Aeromonas) in the soil after 28 days, however, the relative abundance of Verminephrobacter and Muribaculaceae in earthworm gut decreased from 5.6 % to 1.0 % and from 7.3 % to 2.2 %, respectively. After introducing MPs, the relative abundance of Verminephrobacter and Aeromonas (intestinal dysbiosis markers) in earthworm gut enhanced from 5.6 % to 13.5 % and from 0.2 % to 3.1 %, respectively. Co-exposure to atrazine and MPs increased the relative abundance of Bacteroidota. Single or binary of atrazine and MPs have adverse effects on metabolism of gut microbiota. The results revealed the adverse effects of MPs and atrazine on microorganisms in soil and earthworm gut, deepening the knowledge of the influence of MPs and atrazine on soil ecology.