Bioaccumulation Of Microplastics In Different Tissues Of Zebrafish

Microplastics(MPs)are widespread in freshwater environments and can be ingested by aquatic organisms with potential harm.However,the current bioaccumulation process of microplastics is still unclear,and the factors and mechanisms affecting bioaccumulation are still unknown,which results in the ecological risks are difficult to confirm.In order to clarify the scientific issue of the key factors affecting bioaccumulation,we used the freshwater model organism zebrafish(Danio rerio)as the test organism,and selected the green fluorescent polyethylene(PE)particles(10-20 ?m,45-53 ?m and 250-300 ?m)as experimental materials.To understand to process of biological accumulation of MPs in zebrafish,the following aspects were investigated:1)the uptake,elimination and tissue distribution process of microplastics were analyzed by water exposure tests in zebrafish to indicate the influence of particle-size of MPs as well as their time effects;2)the main exposure risks of fishes were discussed via both of water and feeding exposure.The results show that,1)10-300 ?m PE particles could be ingested by zebrafish,and feeding exposure was the major exposure way;2)zebrafish preferred to uptake the larger MPs(250 ?m)which particle size is close to the size of their ordinary food;however,when exposing with mixed particles(10-300 ?m),the number of smaller size microplastics ingested by fishes was higher than that of larger ones,which may due to the adhesion of smaller particles to larger ones;3)the existence of food increased the uptake and elimination of microplastics by zebrafish;4)with the particle size increasing,the proportion of microplastics in the zebrafish intestine increased,which indicated that larger microplastics were not easy to eliminate;5)with the extension of exposure time,the elimination of microplastics by zebrafish increased,after continuous exposure for 28 days,the elimination rate of microplastics with particle size of 20 ?m was 94%.In summary,the study found that there were three factors affecting the accumulation of microplastic in the zebrafish,which were the size of microplastic,the exposure pathway and the exposure time.The particle size is one of the key factors which affect the bioaccumulation of MPs in zebrafish,and the elimination and distribution of microplastics in tissues presented size-effect and time-effect relationship.Feeding exposure is the main way of zebrafish ingest microplastics.This study investigated the uptake,elimination and tissue distribution of microplastic particles by freshwater model organisms(zebrafish),and analyzed the bioaccumulation kinetics process of microplastics,which provide theoretical basis for the accumulation mechanism of microplastics in organisms and can provide scientific support for the ecological risk research of microplastics.