Single Toxicity Of Micro(Nano)plastics To Amphidinium Corterae Hulburt And Joint Toxicity With Nanometer Titanium Dioxide

In recent years,microplastics have attracted worldwide attention for their extensive and lasting pollution characteristics.The ocean is considered as the final destination of microplastics.At present,people have carried out a large number of investigations and studies on the distribution of microplastics in marine and other environments,but there are few studies on the bioaccumulation and biological effects of microplastics in seawater and the compound toxicity of microplastics and other pollutants in the environment.Polystyrene microspheres with particle sizes of 74 microns(74 ?m MPs),3 microns(3 ?m MPs)and 50 nanometers(50 nm NPs)and P25 nano-titanium dioxide(nTiO2),which are widely used in industrial production,were selected as pollutants in this paper to study their single and joint toxicity to harmful red tide algae species Amphidinium carterae Hulburt(A.carterae).First of all,the study on the single toxicity of 3 ?m MPs and 50 nm NPs to A.carterae within 240 h found that the inhibitory effect of micro(nano)plastics on the growth of algae cells depends to a large extent on the concentration and time of exposure.During the long-term continuous culture,high concentration of micro(nano)plastics had sustained harm to microalgae,and would lead to the growth of microalgae entering the decline phase in advance.The particle sizes of micro(nano)plastics had a significant impact on the toxicity of microalgae.The toxicity of 50 nm NPs to microalgae was greater than 3?m MPs from the growth inhibition rate and the oxidative stress to microalgae.In addition,micro(nano)plastics could cause microalgae cell damage,including cytomembrane oxidation,cytomembrane permeability increase and cytomembrane deformation,which was most significant when microalgae grow to the decline phase.The study on the effects of 3 p,m MPs and 50 run NPs on the hemolytic toxin content of A.carterae within 240 h found that the high concentration of 3 ?m MPs and 50 nm NPs can significantly reduce the content of extracellular toxin during the decline phase of the growth of A.carterae,which is probably caused by the adsorption of hemolytie toxin by micro(nano)plastics.At the same time,they could also cause the hemlytic activity of intracellular toxin to increase significantly during the decline phase,which may be closely related to the intensity of oxidative stress on algae cells.The hemolytic activity of intracellular toxin corresponding to 50 nm NPs with the same concentration is significantly higher than 3 um MPs.In the study on the joint toxicity of micro(nano)plastics and nTiO2 on A.carterae,the joint toxicity of three different sizes of micro(nano)plastics,it was found that the toxicity of three kinds of micro(nano)plasties and nTiO2 to microalgae was:nTiO2>50 nm NPs>3 ?m MPs>74 ?m MPs.the inhibition of four pollutants to microalgae growth had obvious dose-effect relationship,and the joint toxicity of micro(nano)plastics and nTiO2 is antagonistic.In the joint toxicity,the antagonism between micro(nano)plastics and nTiO2 has a certain correlation with the size of micro(nano)plastics,the smaller the size of plastics,the stronger the antagonism,which is related to the different adsorption capacity of micro(nano)plastics to nTiO2.