多环芳烃(PAHs)污染对滨海湿地入侵植物互花米草的影响

Effects of polycyclic aromatic hydrocarbons(PAHs) contamination on invasive plant Spartina alterniflora in coastal wetlands

滨海湿地生态系统正遭受着人为活动或自然因素的威胁,为探究多环芳烃（PAHs）污染对滨海湿地入侵植物互花米草根际、根内微生物的影响及植物-微生物联合修复PAHs的潜力,设置含有不同浓度菲和芘的沉积物处理,通过盆栽实验对互花米草幼苗进行暴露.结果显示,培养70 d后,菲和芘的去除率分别为13%-36%和11%-30%;菲处理的互花米草根际沉积物中脱氢酶活性显著高于对照（P〈0.05）,非根际沉积物多酚氧化酶活性则降低10%.磷脂脂肪酸（PLFA）分析显示,菲处理显著降低了根际沉积物微生物量（P〈0.05）,尤其是革兰氏阴性菌下降了24%;而芘处理对脱氢酶、多酚氧化酶以及总微生物量的影响相对较小.100 mg/kg菲处理使得根际与根内革兰氏阴性菌PAHs-环羟基双加氧酶基因（PAH-RHDα-GN）丰度比对照组分别增加了100倍和3倍;而100 mg/kg芘处理使得根际与非根际沉积物中PAH-RHDα-GP丰度显著升高（P〈0.05）.上述结果表明,入侵植物互花米草对PAHs污染存在明显的响应,其根内细菌在植物-微生物联合修复PAHs污染具有重要的作用.

The functions of coastal wetland ecosystems are increasingly threatened by anthropogenic and natural factors. This study aimed to investigate the effects of polycyclic aromatic hydrocarbons（PAHs） on rhizosphere and endophytic bacterial communities of invasive plants（Spartina alternif lora） and the plant-microbe associated bioremediation potential of PAHcontaminated sediments. Based on pot experiments, S. alterniflora was selected and cultivated under different concentrations of phenanthrene（PHE） and pyrene（PYR） contaminated sediments（for 70 d）. The results indicated that the amount of PHE removed from the sediments ranged from 13% to 36%, whereas PYR ranged from 11% to 30%. In rhizosphere sediments, dehydrogenase activities were significantly（P 0.05） enhanced by higher concentrations of PHE treatments, whereas polyphenol oxidase activities were prohibited by greater than 10% in non-rhizosphere sediments. Compared with the control, PHE treatments had significantly（P 0.05） lower total microbial biomass（phospholipid fatty acids, PLFA）, especially for gram-negative bacteria with more than a 24% decrease. However, the PYR treatments had little effect on the dehydrogenase, polyphenol oxidase, and total PLFA biomass. The greatest abundance of PAH-ring hydroxylating dioxygenases（PAH-RHDα-GN） isolated from the gramnegative bacteria of rhizoplane and endophyte in roots were found in the 100 mg/kg PHE treatment and increased by more than 100-and 3-fold, respectively. The greatest abundances of PAH-ring hydroxylating dioxygenases（PAH-RHDα-GP） isolated from gram-positive bacteria of rhizosphere and non-rhizosphere were significantly enhanced in the 100 mg/kg PYR treatment. These results suggested that PAH pollution will result in a comprehensive effect on S. alterniflora, whose endophytic bacteria might play an important role in the plant-microbe associated bioremediation potential of PAH contaminated sediments.