Effects of polylactic acid microplastics on the recruitment of cyanobacteria from sediments
Sediments are important sites for cyanobacteria overwintering,and also be the sinks of microplastics(MPs)and nutrients.In this study,a laboratory experiment was conducted to explore the effects of biodegradable poly lactic acid microplastics(PLA-MPs)on the recruitment of dormant cyanobacteria from sediment.Different content(0,0.05％,0.5％,5％,w/w)of PLA-MPs were added to the sediment and then incubated under 15℃,with light intensity of 40μE/(m2.s)for 50days.Results showed that addition of 0.5％and 5％of PLA-MPs significantly increased the concentrations of NH4+-N and NO3--N(P＜0.05)in the overlying water,which was 61.19 and 84.94 times,5.80 and 17.01 times higher than that in the control,respectively.This was linked with the increase in the abundances of nitrogen fixation(nifH),nitrification(AOB-amoA、nxrB)and the reduction of denitrification(narG)genes.Besides,the abundance of the phoD gene that involved in organophosphorus mineralization,the oxygen penetration depth in sediment were also decreased with the presence of PLA-MPs,which probably promote the release of sedimentary phosphorus.Moreover,the relative abundance of the cyanobacterial phylum in the water increased significantly with the increase in PLA-MPs content,which was 12.38％,23.53％and 28.54％higher than that of the control group,respectively,indicating that PLA-MPs promoted the recruitment of sedimentary cyanobacteria.These findings may extend the current understanding of the potential aquatic risk of biodegradable PLA-MPs.
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维普
