Study The Response Of Freshwater Microalgae To Suspended Particles,antibiotics And Combined Stress

The suspended particulates and antibiotics in water body could affect the physiology,ecology and diversity of phytoplankton,which are likely to affect the stability of the entire aquatic ecosystem.In order to investigate the effects and mechanism of suspended particulate and antibiotics on the algae,this research chose the natural nanoparticles(NNPs),florfenicol(FF)and thiamphenicol(TAP)as target,use M.flos-aquae(cyanobacteria)and C.pyrenoidosa(green algae)as tested subjects,investigated the mechanism of freshwater microalgae in response to the stress of NNPs,FF and TAP,by determining the physiological and biochemical characteristic,photosynthetic activity,cell cycle and apoptosis.The results indicated:(1)Under the stress of NNPs,FF and TAP,the CAT,SOD activity and the content of MDA in M.flos-aquae and C.pyrenoidosa cells were affected,while the effect of low concentration is smaller than the high concentration.(2)Compared to the single antibiotics treat after the antibiotics and NNPs compound the effects on algae is that the induction of antioxidant enzymes in M.flos-aquae was enhanced,and the induction of C.pyrenoidosa was weakened.(3)NNPs promoted the chlorophyll a content of M.flos-aquae,and had a significant inhibitory effect on C.pyrenoidosa.Other photosynthetic activities of the two microalgae have different effect,show differences between species.(4)FF and TAP had shown a “low concentrations promotion and high inhibition”phenomenon on the chlorophyll a content and “low concentrations low impact and high concentrations promotion” to the other photosynthetic parameters of M.flos-aquae,may be attributed to the response of the body to reduce the damage caused by the decrease in chlorophyll a content.Similar results were found after the addition of NNPs.However,the degree of promotion and inhibition was not the same,and the effect of low concentration was enhanced and the inhibition of high concentration was weakened.The effects of FF and TAP on chlorophyll a content of C.pyrenoidosa present “low concentrations promotion and high concentrations inhibition” phenomenon and “low concentrations low impact and high concentrationshigh inhibition” to the other photosynthetic parameters.After the composite with NNPs,the inhibitory effect of high concentrations of antibiotics on the photosynthetic activity of the protein globule algae was more significant.(5)Effect of low concentrations(?100 mg/L)NNPs,(<1 ?g/L and 1 mg/L)FF and TAP on M.flos-aquae and C.pyrenoidosa cell cycle and apoptosis had little effect,while high concentrations of NNPs,FF and TAP(?150 mg/L,?1 ?g/L and 1 mg/L)the cells were mainly blocked in G0/G1 phase(M.flos-aquae)and in G0/G1 and S phase(C.pyrenoidosa),and the higher the concentrations of NNPs and antibiotics lead to the greater the apoptotic rate.After the composite of antibiotics with NNPs,the effect on M.flos-aqu cell cycle and apoptosis is weak;and the influence of C.pyrenoidosa cell cycle and apoptosis is enhanced.