苦草及茎叶附着微生物净化水质的昼夜变化

Diurnal Variation of Vallisneria and Microorganisms Attached to the Stems and Leaves for Water Purification

沉水植物的茎叶附着了大量微生物,其光合作用的主要场所在茎叶,目前在沉水植物光合作用和呼吸作用下,茎叶附着微生物对水体脱氮除磷效果的昼夜变化规律尚不明晰。选用典型沉水植物苦草,培养一段时间后清洗部分茎叶附着物,与未经清洗的苦草进行对比,观察24 h内两组苦草所在水体DO、ORP等指标的变化情况,以N、P浓度变化表征茎叶微生物发生的脱氮除磷反应,并结合显微镜、高通量测序技术进行综合分析。结果表明,茎叶附着微生物量少的苦草所在水体的DO昼夜差值达9.1 mg/L,其他指标波动较小;茎叶附着微生物量多的苦草所在水体的DO和ORP分别在0~3.7 mg/L和0~150 mV之间昼夜波动。日间水体NH_(4)^(+)-N下降、NO_(3)^(-)-N升高、PO_(4)^(3-)-P和TP下降,发生硝化、好氧反硝化、除磷反应;夜间N、P指标的变化与日间相反,发生反硝化和释磷反应。苦草茎叶附着好氧、兼氧及厌氧多种类型的微生物,优势菌门为Proteobacteria等,优势菌属为norank_f__Rhizobiales_Incertae_Sedis等,丰度排名前20的优势菌属中与脱氮除磷相关的功能菌属共14种,其中反硝化菌属10种,为主要功能菌属,占比为36.43%,包括Hyphomicrobium、Rhodobacter、unclassified_f__Rhizobiaceae 3种好氧反硝化菌。在沉水植物与茎叶附着微生物的共同作用下,水体净化昼夜变化机理类似于间歇曝气、周期为24 h、附着生长的SBR工艺运行原理。

A large number of microorganisms are attached to the stems and leaves of submerged plants,and their main photosynthetic sites are in the stems and leaves.At present,the diurnal variation of nitrogen and phosphorus removal performance of stem and leaf attached microorganisms under photosynthesis and respiration of submerged plants is still unclear.In this paper,part of the stems and leaves of a typical submerged plant Vallisneria were cleaned after culture for a period of time to make a comparison with the uncleaned stems and leaves.The changes of DO,ORP and other indicators of the water bodies with two kinds of Vallisneria were observed within 24 h.The nitrogen and phosphorus removal reactions of the microorganisms attached to stems and leaves were characterized by changes in N and P concentrations,and combined with microscopy and high‑throughput sequencing technology for comprehensive analysis.The diurnal difference of DO in the water with less stem and leaf attached microorganisms was 9.1 mg/L,and the other indexes fluctuated little.The DO and ORP of the water with abundant stems and leafs attached microorganisms fluctuated in the range of 0-3.7 mg/L and 0-150 mV,respectively.During the daytime,the NH_(4)^(+)-N in water decreased,the NO_(3)^(-)-N in water increased,and PO_(4)^(3-)-P and TP in water decreased,indicating that nitrification,aerobic denitrification and phosphorus removal reactions occurred.The changes of N and P indexes at night were opposite to those during the daytime,and denitrification and phosphorus release reactions occurred.There were many types of aerobic,facultative and anaerobic microorganisms attached to the stems and leaves of Vallisneria.The dominant bacterial phylum was Proteobacteria,and the dominant bacterial genus was norank_f__Rhizobiales_Incertae_Sedis.Among the top 20 dominant bacterial genera in terms of abundance,there were 14 functional bacteria related to nitrogen and phosphorus removal,of which 10 were denitrifying bacteria with relative abundance of 36.43%,including 3 aerobic denitrifying bacteria Hyphomicrobium,Rhodobacter and unclassified_f__Rhizobiaceae.The mechanism of diurnal change of water purification under the joint action of submerged plants and stem and leaf attached microorganisms was similar to the operation principle of attached growth SBR process with intermittent aeration and cyclic time of 24 h.