Enrichment And Toxicity Effects Of Microplastics In Aquatic Food Chain

Microplastics(MPs)refer to plastic fragments or particles with a particle size of less than 5 mm or 1 mm.In this paper,we investigated the enrichment and impact of MPs in aquatic organisms.Using the polyethylene particles(PE)as the experimental material and the cladoceran Daphnia magna as the main test organism:1)The uptake and depuration of PE particles in D.magna were measured under laboratory controlled experimental conditions;2)Joint biotoxicity of PE particles and phenanthrene(phe)were determined;3)The distribution of PE particles in tissues of zebrafish under different exposure modes(water environment exposure,food exposure and water environment + food exposure)were estimated.The results show that:1)The PE particles(10-20 μm)were likely to be ingested and egested by D.magna,the number of PE in D.magna increased up to maximum after 1 h exposure(102 particles/ind)and decreased 95%after 30 min of clearance;2)Uptake and depuration of PE particles in D.magna decreased by 78.3%when 106 cells/mL food(Chlorella vulgaris)were added;3)The feeding rates of D.magna in the PE particles exposure group significantly decreased by 73.4%,65.4%and 41.1%respectively after 0.5,1 and 1.5 hours feeding compared with the control group;4)The EC50 of PE particles(1-10 μm)of D.magna for 48 h was 7.75 mg/L(1.55×107 particles/mL);5)EC50 values of phe was 0.35 mg/L after 48 h joint toxicity test with PE and phe,the combined toxic effect of PE and phe are synergy;6)The PE particles were ingested by zebrafish through the water environment and food,and the main method to uptake PE particles for zebrafish was water environment exposure in this experimental conditions:7)The PE particles mainly presented in the digestive tract of zebrafish and were more easily eliminated through excretion in the presence of food(D.magna).This study explored the uptake and eliminate of MPs with freshwater model organisms,the joint toxicity of MPs and organic pollutants and the food chain transfer process.The results of the research provided more basic data to investigate MPs enrichment and ecological risk evaluation in freshwater environment.