Evaluation And Research On The Effect Of Nanoplastics On Artemia Tissue

The excessive use and low recycling rate of plastic products is becoming more and more severe,and the related plastic pollution to the environment has attracted global attention.As a nanomaterial,nanoplastics can interact with cells and organisms in various ways,thereby having impacts on organisms,threating to plankton and their predators.Artemia is a typical non-selective filter-feeding zooplankton.Due to its unique biological and reproductive characteristics,Artemia has been widely used as an experimental organism for ecotoxicological study in marine environment.In this study,parthenogenetic Artemia was used as an experimental animal to explore the effects of polystyrene nanoplastics(PSNPs)on the growth and survival,gut tissue histology,gut microflora diversity,reproductive performance and blood cell hemogram of Artemia.The aim of this study is to illustrate the physiological toxicity of nanoplastics on Artemia,and to further evaluate its harm to marine zooplankton and marine ecosystems.The conclusions of the thesis are as follows:The microscopic observation showed that PSNPs are uniformly dispersed in Milli-Q water,while they were aggregated in 35 g/L artificial seawater with maximum size of 30μm.PSNPs can be ingested by Artemia nauplii into the gut and excreted in the form of fecal balls.When exposing Artemia to PSNPs in a concentration range of 0.05-50 μg/mL for 14 days,no significant difference was observed in Artemia survival rate at PSNPs concentrations of 0.05,0.5 and 5 μg/mL(p>0.05);however,the survival rates of Artemia in the 25 μg/mL and 50 μg/mL groups were significantly lower than that in the other groups(p<0.05).During the first 6-day exposure,the body lengths of Artemia in the 25 μg/mL and 50 μg/mL groups were significantly lower than that of the control group(p<0.05),and the body lengths of Artemia in the other groups were not significantly different in control group(p>0.05).It showed that although PSNPs accumulate in seawater,they could be ingested by Artemia,high concentration of PSNPs reduced Artemia survival and body length in the short term.Through HE and Hocehst staining of Artemia gut tissues in PSNPs concentrations of 0.05 and 0.5 μg/mL,compared with the control group(Ctrl),it was found that Artemia epithelial cells in midgut were detached and arranged irregularly when exposed to PSNPs at a concentration of 0.5 μg/mL,indicating that PSNPs exposure resulted in the gut damage.High-throughput analysis on Artemia gut microflora in PSNPs groups at concentrations of 0.5 and 5 μg/mL(PS0.5 and PS5)showed that,compared with the control group(Ctrl),the abundance indexes of Artemia gut microflora,i.e.,Chao 1 and Ace index increased,and Chao 1 index in the 5 μg/mL group was significantly higher than that in the control group(p<0.05).Proteobacteria,Actinomycetes,Firmicutes and Bacteroides were the main the phylum in Artemia gut.LEf Se analysis showed that Class Proteobacteria,Order saltwater Sphaerobacteria and Family saltwater Sphaerobacteria were the uniquely presented in the PS5 group,while Order Lactobacillus and Family Rhodobacter were only detected in the Ctrl group(p<0.05).In summary,PSNPs damaged Artemia midgut epithelial cells and significantly increased the microbial abundance of Artemia gut.The Artemia blood cells were taken out and fixed with glutaraldehyde.Compared with the control group,the Artemia blood cells in the 5 μg/mL group exposed to PSNPs were significantly differentiated in morphology and blood phase.Artemia granulosa cells decreased in the PSNPs group,and the number of phagocytes continued to increase(particularly the granulosa cells).It showed that PSNPs may regulate the plasticity of Artemia blood cells.For the PSNPs 5 μg/mL group,the developmental duration from the newly hatching Artemia nauplii to the first brood of adult,and the time interval between each brood were significantly higher than those in the control group and the PSNPs 0.5 μg/mL group(p<0.05).The total number of Artemia progeny in the 5 μg/mL PSNPs group was significantly lower than that of the control group and PSNPs 0.5 μg/mL group(p<0.05).Thus,exposure to PSNPs prolonged maturation and time interval of each brood,and reduced the number of Artemia offspring.In summary,the presence of PSNPs in seawater have negative or toxic effect on the growth and physiological processes of Artemia.Our study provides support for studying the toxic effect of PSNPs and its histological mechanism,and lays a foundation for further elucidating the molecular mechanism of PSNPs toxic effect on marine invertebrates.