沉水植物根际微生物群落结构及其对磷迁移转化的影响

Anthropogenic eutrophication is a persistent environmental problem that impacts aquatic ecosystems worldwide.To assess the source and possible mechanisms of internal P loading is a critical factor to predict future water quality and to succeed eutrophication control programs.Submerged macrophytes play a key role in the physical structuring of shallow lakes. Microbial activities in submerged macrophytes bed sediments are higher than found in nearby non-vegetated sediments.Sediment bacteria play a key role in organic P mineralization and the release of P from the sediment,both directly and indirectly. The overarching goal of this proposed work is to focus on the direct effect of microbial community structure in the surrounding rhizosphere of submerged macrophytes on phosphorus cycling. Both mesocosm experiments and fields researches will be set up, where the two different naturally developed submerged macrophytes (Vallisneria americana, Potamogeton crispus) cover. Molecular methods including automated ribosomal intergenic spacer analysis(ARISA) and catalysed reporter deposition fluorescence in situ hybridization (CARD-FISH) will be used to study temporal dynamics of the bacterial community in the surrounding rhizosphere of submerged macorphytes. SMT,31P-NMR will also be used at the same time to study the phosphorus fractions in the sediment and water. Specific Aims: 1. To characterize the temporal variability of microbial community in the surrounding rhizosphere with two different submerged macrophytes and to identify the factors which have effects on the change. 2.Identify the functional bacterial community which have direct effects on the phosphorus cycling. 3. Set up the coupling relation between the functional bacterial community and the phosphorus cycling.

浅水湖泊沉水植物对水体生产力具有十分重要的影响。根际蕴藏着的丰富微生物资源对沉积物中磷的生物地球化学循环起着关键作用。本课题拟通过室内模拟实验并结合野外调查，选择两类典型的沉水植物群落，应用现代分子生物学技术（ARISA、CARD FISH等）跟踪监测沉水植物生长发育、衰亡及季相交替过程中根际微生物群落结构的动态变化，研究沉水植物群落的生理变化通过根部的呼吸与放氧对微生物群落组成的影响。结合环境化学方法（SMT，31P-NMR）同步监测沉积物，水体以及间隙水中各形态磷的组成、含量及相关理化参数，建立沉水植物根际微生物群落结构与磷迁移转化关系的研究，确定与磷循环相关的功能微生物种群，力求揭示两者之间关系，并阐释其作用机理。为揭示微生物作用下的沉积物中磷的生物地球化学循环机制，水生植物的恢复与富营养化水体的生态治理提供参考。

项目背景：.浅水湖泊沉水植物对水体生产力具有十分重要的影响。根际蕴藏着的丰富微生物资源对沉积物中磷的生物地球化学循环起着关键作用。..研究内容：.1浅水湖泊典型优势沉水植物生长旺盛期，根际微生物群落结构特征及各形态磷分布特征; 2洪泽湖沉水植物生长过程根际微生物群落结构特征及磷迁移转化规律研究;3 沉水植物根际微生物群落结构动态变化特征及磷迁移转化规律的室内模拟研究。..重要结果：.1在生长旺盛期，苦草根际沉积物中，16:00、18:00、18:2ω6c磷脂含量显著高于其他植物；菹草根际革兰氏阴性菌16:1ω7c、18:1ω7c磷脂占优。马来眼子菜根际沉积物中总磷含量最高，无机磷是各沉水植物根际沉积物中总磷的主要组成部分，约占总磷的60%。HCl-P是马来眼子菜根际沉积物无机磷的主要组成，占比约50%-78%。NaOH-P是菹草根际无机磷的主要组成，占比为57%。.2 洪泽湖两种沉水植物（菹草、蓖齿眼子菜）及菹-蓖混丛根际沉积物微生物群落结构在生长周期内发生了显著变化。16:00、16:1ω7c、18:1ω7c磷脂脂肪酸在三种群丛变化显著。影响沉积物微生物群落的因素：不同生长阶段>沉水植物类型。在生长周期内，沉水植物根际沉积物总磷、无机磷、有机磷含量均呈现先降低后升高的趋势。植物生长期，沉积物环境能够促使有机磷向无机磷的转换，增加NaOH-P降低HCl-P，植物衰亡期时，NaOH-P存在向HCl-P转化的趋势。.3 室内模拟实验表明，苦草在生长周期内，革兰氏阳性菌占主要优势，革兰氏阴性菌则随苦草的生长呈下降趋势。苦草生长初期与旺盛期根际微生物群落结构差异度为23.63%，与衰亡期差异度为38.71%，而生长旺盛期与衰亡期根际微生物群落结构差异度为37.69%。生长旺盛期以16:00，18:00革兰氏阳性菌，18:1 w7c，18:1 w9c革兰氏阴性菌为主。生长衰亡期，则以14:00，a15:0革兰氏阳性菌, 18:2 w6c真菌为主。苦草生长有效地减少沉积物中有机质及磷的含量，总磷、有机磷、无机磷分别下降8.97%、7.8%、10.28%。沉积物中TP和IP在培养前75天快速下降，75天之后下降速度变缓。值得关注的是NaOH-P在培养的前75天呈上升趋势。