Effect Of Microplastics On The Oxidative Stress Response And The Intensity Of Carbon Use By The Microbial Community In Earthworms

Plastics brought into the soil by agricultural production activities are gradually broken down into microplastics through the process of weathering.Microplastics are persistent organic pollutants,which accumulate in large quantities in soil environment and harm soil biological health and ecosystem security.Earthworms are sensitive to soil pollutants,so many scholars have used them as indicators to monitor the health of soil ecosystem.In this study,through a filter paper test and an artificial soil test,the Eisenia fetida was used as the test organism,and polyethylene microplastic(PE)was used as the exogenous contaminant,and used a factor analysis and path analysis model to analyze the data.The study focused on: Acute toxic effects of microplastic stress on earthworms,screening of sensitive oxidative stress indicators in head and tail tissues of earthworms under longterm and short-term microplastic stress,changes in the intensity of carbon use by microbial communities in earthworms,and the driving process between oxidative stress and microbial communities in earthworms.The study aimed to elucidate the response of earthworms to microplastic stress in soil and to provide a theoretical basis for early warning monitoring of soil ecosystems.The results of this study are as follows:(1)Most of the symptoms of earthworm poisoning under microplastic stress were paralysis and relaxation.As the concentration and duration of stress increased,the earthworm escape rate increased.Under stress concentration of 2500 mg/kg,death occurred 12 hours and the number of deaths increased to 3 after stress.The earthworm growth inhibition rate fluctuated with increasing stress time and concentration,first increasing,then decreasing and then increasing again.The growth inhibition rate was lower under 500 and 2000 mg/kg treatment,and higher in the treatment with stress concentrations of 1500 and 2500 mg/kg.(2)Under different stress time and stress concentration,the activity(content)of oxidative stress indicators in different parts of earthworm changed.In short-term experiments with artificial soils: The main oxidative stress indicator in head tissues at microplastic concentrations of 1500 and2000 mg/kg for 1-3 d was catalase(CAT);at 4-7 d,glutathione peroxidase(GSH-PX)and Glutathione S transferase(GST)become sensitive indicators of oxidative stress;at 8-10 d,malondialdehyde plays a major role in head and tail tissues at a stress concentration of 2000 mg/kg.In long-term experiments with artificial soils: at 10 d,peroxidase plays an important role in all tissues and concentrations;at 20 d,catalase and GST are sensitive indicators of oxidative stress in caudal tissues;at 30 d,GSH-PX plays a major role in stress concentrations of 1000 and 2000 mg/kg head tissue.(3)Under microplastic stress,the microbial community of earthworms changes its intensity of use of different types of carbon sources.Under low concentrations(100 and 500 mg/kg)of microplastic stress,the microbial community in earthworms mainly uses carbohydrate-based carbon sources.At 1000 mg/kg to 1500 mg/kg,the microbial community in earthworms mainly uses carboxylic acid carbon sources.At 2000 mg/kg,carbohydrate carbon sources have once again become the most intensive carbon sources.(4)In the concentration range designed for this experiment,the microbial community in the earthworm plays a major role in regulating the total protein content of the earthworm.Under low LDPE stress,the protein content of earthworms enhanced.At 1000 mg/kg,antioxidant enzymes have high effect coefficient.Stressed by 1500 mg/kg,the total coefficient of microbial communities increased.With increasing stress concentration(2000mg/kg),Protein content and the total coefficient of microbial communities in earthworms increased.