菲在红树林不同根际距离中的降解及微生物群落结构变化

Degradation of phenanthrene in mangroves at different rhizo⁃sphere distances and changes in microbial community structure

【目的】研究菲(Phe)在不同根际距离中的降解和根际区域微生物群落结构变化,获得最佳降解效果的根际距离和降解微生物种类,为阐明红树林根际效应对海岸带多环芳烃(PAHs)降解的强化作用和机制提供参考。【方法】利用根际箱分离4个连续的隔间,其距离分别为0~2 mm、2~4 mm、4~6 mm隔间(根际)和>6 mm隔间(非根际),分别于0、10、20、30、40和50 d测定不同根际距离的Phe残留浓度、沉积物理化性质、微生物生物量和细菌群落结构,并采用冗余分析(RDA)探明Phe残留浓度与环境因子及细菌群落结构的相关性。【结果】靠近根际表面的沉积物(0~2 mm隔间)Phe降解效率最高(74.73%)。在培养50 d后,对比不同隔间的理化性质变化,与第0 d相比,0~2 mm隔间变化最明显,p H降低3.84%,有机质含量提高16.14%;>6 mm隔间腐殖质含量升高12.56%。在Phe降解过程中,沉积物pH和腐殖质含量随着红树林根际距离的增加而增加,有机质含量随着根际距离的增加而减少。培养50 d后,微生物量碳(MBC)、微生物量氮(MBN)和微生物呼吸强度(SMR)在0~2 mm隔间均最高,分别为216.45 mg/kg、68.20 mg/kg和147.35 mg/(kg·h),且均随着根际距离增加而降低。培养结束后,在0~2 mm、2~4 mm和4~6 mm隔间优势细菌属中,短杆菌属(Brevibacterium)和乳酸杆菌属(Lactobacillus)的相对丰度随根际距离的增加而减少,脂环酸芽孢杆菌属(Alicyclobacillus)的相对丰度则随根际距离的增加而增加。RDA结果表明,Phe残留浓度主要受降解功能微生物及环境因子影响,与脂环酸芽孢杆菌属、盐硫杆菌属(Halothiobacillus)、硫单胞菌属(Thiomonas)、短杆菌属、乳酸杆菌属及有机质呈负相关。【结论】红树林根际效应可通过影响根际区沉积物的理化性质,从而改变细菌群落结构和微生物活性,以强化Phe降解,对消除海岸带生态系统中PAHs污染具有积极影响。

【Objective】The purpose was to study the degradation of phenanthrene(Phe)in different rhizosphere distances and the structural changes of microbial community in the rhizosphere region,and to obtain the rhizosphere distances and degrading microbial species with the best degradation effect,in order to provide reference for elucidating the enhancement of mangrove rhizosphere effects on the degradation of polycyclic aromatic hydrocarbons(PAHs)in the coastal zone and its mechanism.【Method】In this study,four consecutive compartments with rhizosphere distances of 0-2 mm,2-4 mm,4-6 mm(rhizosphere)and>6 mm(non-rhizosphere)were separated using rhizosphere boxes,and the Phe residue concentration,sediment physicochemical properties,microbial biomass and bacterial community structure were determined at different rhizosphere distances at 0,10,20,30,40,and 50 d.Redundancy analysis(RDA)was used to investigate the correlation between Phe residue concentration and environmental factors and bacterial community structure.【Result】The results of the study showed that the Phe degradation efficiency(74.73%)was the highest in the sediments close to the rhizosphere surface(0-2 mm compartment).After 50 d of incubation,the physicochemical properties of different compartments were compared.Compared with 0 d,the most great changes were observed in the 0-2 mm compartment,with a decrease of 3.84%in pH and a 16.14%increase in organic matter content;humus content was elevated by 12.56%in the>6 mm compartment.During the degradation process of Phe,the pH and humus content of the sediment increased with the increase of the rhizosphere distance of the mangrove forests,and the content of organic matter decreased with the increase of the rhizosphere distance.After 50 d of incubation,microbial biomass carbon(MBC),microbial biomass nitrogen(MBN)and microbial respiratory strength(SMR)were the highest in the 0-2 mm compartment in general,which at 216.45 mg/kg,68.20 mg/kg and 147.35 mg/(kg·h)respectively,and all of them decreased with the increasing of rhizosphere distance.At the end of incubation,in the dominant functional genera of 0-2 mm,2-4 mm and 4-6 mm compartments,relative abundance of Brevibacterium and Lactobacillus continued to decrease with the increasing of rhizosphere distance,and relative abundance of Alicyclobacillus continued to increase with increasing of rhizosphere distance.RDA showed that Phe residue concentration was mainly affected by degradation function microorganisms and environmental factors,and was negatively correlated with Alicyclobacillus,Halothiobacillus,Thiomonas,Brevibacterium,and Lactobacillus,as well as organic matter.【Conclusion】Mangrove rhizosphere effects can enhance the degradation of Phe by affecting the physicochemical properties of sediments in the rhizosphere zone,thereby changing the structure of bacterial community and microbial activity,and have a positive impact on the elimination of PAHs pollution in the coastal zone ecosystem.