Effects Of Polyethylene(PE) Microplastics On Long-term Ecotoxicological Effects Of Earthworm(Eisenia Foetida)

Microplastics as a new type of pollutant are receiving increasing attention,and the mainstream research direction is gradually shifting from the ocean to land.Earthworms,as important model organisms in soil toxicology experiments,are one of the indicators for evaluating soil health.In order to fill the gap in the long-term effects of microplastics on organisms,this study selected non-degradable microplastics polyethylene as the experimental material,and the red wiggler worm(Eisenia foetida)as the experimental organism,to analyze and test changes in the biomass,mortality rate,functional enzyme activity in the gut,and gut microbiome of parent earthworms,as well as the gut microbiome of their offspring.The changes in bacterial community structure in the gut contents of parent and offspring earthworms were compared and analyzed to obtain response characteristics of whether the offspring earthworms would develop a certain level of resistance to microplastics.The main conclusions are as follows:(1)The study found that the higher the concentration of microplastics,the greater the loss of earthworm biomass and mortality rate.When the earthworms were satiated,they showed avoidance behavior towards soil containing microplastics,while hunger did not show a significant avoidance response.The concentration and particle size of microplastics were related to the earthworm’s egg-laying amount,and higher concentrations had a promoting effect on the earthworm’s egg-laying,but the influence of particle size was also important.In different particle size treatments,microplastics had different toxic effects on earthworms,but earthworms cleared peroxides and free radicals in the body by increasing GST activity to avoid oxidative damage.However,under certain conditions,the earthworm’s adaptation mechanism may lead to a decrease in GST activity.(2)Adding microplastics to the soil significantly reduced the ACE index and Chao diversity index of the gut microbiota,while the Shannon diversity index slightly decreased or increased depending on the treatment.The size and concentration of microplastics can affect the diversity of the earthworm’s gut microbiota.The dominant bacterial phyla in the earthworm’s gut microbiota changed due to microplastic pollution,and some of these changes may affect the earthworm’s health and adaptability,as well as their role in ecosystem function.The study also found that microplastics may be related to various biomedical pathways,including diseases,cellular function,signaling,and metabolism.(3)Microplastics of different concentrations and particle sizes may alter the gut ecological environment of earthworms,leading to metabolic and functional imbalances in microorganisms,thereby affecting their survival and reproduction.Decreasing particle size and increasing concentration of microplastics may both lead to a decrease in bacterial diversity.Different types and sizes of microplastics have different toxicities and impact effects,and the relative abundance of gut microbiota in offspring earthworms varies under different treatment conditions.(4)There are significant differences in the pathways in the gut of parent earthworms and offspring earthworms.The pathways related to co-factor biosynthesis,carbon metabolism,and amino acid biosynthesis are ranked higher in the gut of offspring earthworms,while those related to neurodegenerative pathways,ribosomes,cellular aging,and Alzheimer’s disease are ranked higher in the gut of parent earthworms.In conclusion,the concentration and particle size of microplastics can lead to biomass loss and mortality increase of earthworms,and also affect the avoidance response of earthworms.Microplastic pollution also affects the diversity and ecological environment of the gut microbiota of earthworms,possibly affecting the health and adaptability of earthworms,as well as the functioning of ecosystems.In addition,there were significant differences in the intestinal pathways between the parent earthworms and the offspring earthworms,and the metabolic pathways of the offspring earthworms ranked higher.