Combined Toxicity of Microplastics and UV Filters on Chlorella sp.in Marine Environment
Microplastics and UV filters,as emerging pollutants that are persistent and difficult to degrade,have raised worldwide concern in recent years.However,their combined toxic effects on marine microalgae are still unknown.In the present study,a batch of 7-day combined exposure experiments of polystyrene microplastics(PS-MPs,1 μm,10 mg·L-1)and the organic UV filter butyl methoxydibenzoylmethane(BMDM,50 μg·L-1 and 500 μg·L-1)were performed in Chlorella sp.Growth inhibition,surface topography and physical characteristics,photosynthetic pigment content,oxidative stress level,and extracellular polymeric substance(EPS)content of microalgae were analyzed.The results showed that the inhibition rates of Chlorella sp.were up to 26.15％and 42.05％under the single BMDM exposures at 50 μg·L-1 and 500 μg·L-1,respectively,while they were lower as 15.38％and 17.95％under combined exposures of BMDM and PS-MPs.Atomic force microscopic observation showed less dents and wrinkles on the surface of Chlorella sp.after combined exposures compared to those observed after exposure to BMDM alone.The surface viscosity and roughness of Chlorella sp.tended to decrease,along with a decrease in glutathione content and oxidative stress response.In addition,the EPS synthesis in Chlorella sp.was significantly lower in the groups exposed to both pollutants compared to those exposed to BMDM alone,with lower phycobiliproteins content and higher cell density of Chlorella sp.Our study suggests that the addition of PS-MPs could reduce the BMDM toxicity to Chlorella sp.in marine environment.
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