Microplastics Distribution In Haikou Bay And Their Toxicological Effects On Microalga Chaetoceros Muelleri

In modern society,people use a lot of plastic products,making plastic waste widespread in the world.Meanwhile,microplastic pollution has gradually attracted everyone's attention.In order to further investigate microplastic pollution,this paper mainly focused on the following contents:1)elucidated the occurrence and distribution of microplastics in Haikou Bay,in terms of abundance,size,shape,color,composition,and other potential contributors.2)investigated the toxicological effects of microplastics on microalgae,by studying the microplastics(i.e.polystyrene,short for mPS;polyethylene terephthalate,short for mPET)with different particle sizes and different concentrations on cell growth of Chaetoceros muelleri.3)investigated the single and combined toxicological effects of microplastics and Benzo(a)pyrene(short for B[a]P)on microalgae,mainly tested their effects on cell growth and antioxidant enzymes of microalga C.muelleri.The main results of this study were summarized as follows:(1)A moderate abundance(0.26-0.84 n/m~3)of microplastics was observed in samples collected from Haikou Bay in the northern South China sea.Our work demonstrated that microplastic abundance differs geographically according to the presence of functional zones near each of eight sampling sites in Haikou Bay,and in particular higher concentrations of microplastics in seawater and sediment were attributed to public beaches and a sewage drainage ditch,respectively.The common types of microplastics were identified to be fibers with rayon over wide range of 1–1.9 mm in seawater,and fibers with Polyethylene at 1–1.9mm in sediment.(2)For the same type of microplastics,the smaller the size of the microplastics(100?m)and the greater the concentration(200 mg/L)could seriously inhibit the growth of C.muelleri.The effect of mPET on the dry cell weight of C.muelleri showed a decrease trend,which was not significantly different from the control.For mPS,it does not affect the dry cell weight on C.muelleri.Compared with the control,the effect of mPET on chlorophyll a of C.muelleri was unchanged and then decreased,while for mPS,the content of chlorophyll a firstly decreased and then increased.(3)The addition of single mPET significantly inhibited the growth of C.muelleri,but no inhibition caused by mPS.This may be related to the differences in chemical properties of microplastics.In addition,the aggregation and precipitation of mPET were observed in the culture,which may be also one of contributors to the negative impact on microalgae.The results showed that the B[a]P at high concentration of 150?g/L significantly inhibited the growth of C.muelleri accompanying with the reduction of SOD.Furthermore,the mixture of microplastics and B[a]P had significant inhibition on the growth of C.muelleri,while the combination of B[a]P with mPET has stronger inhibitory effects on cells as compared with mPS,owing to less B[a]P was absorbed on mPET.