The effects of adsorptive materials on microbial community composition and PAH degradation at the sediment capewater interface

Capping with layers of inert or adsorptive materials is used to control the release of polycyclic aromatic hydrocarbons(PAH)in sediment but little is known about microbial degradation processes in these materials.A rich native microbial community inhabits the sediment bed,and capping media can influence enrichment and biodegradation activity of benthic microorganisms.The aim of this study was to evaluate the effects of capping media(sand,organoclay,and powdered activated carbon[PAC])on microbial communities under oxic conditions typical of the capewater interface,where naphthalene degradation(model PAH)is likely to be maximized.Bench scale experiments compared naphthalene concentrations,nahAc biomarker abundance,microbial community composition,and cellular attachment in systems amended with adsorptive and non-adsorptive capping materials.Results indicate that activated carbon promoted and enhanced bioactivity;PAC treatments showed high biodegradation rates,nahAc biomarker levels,and attached biological growth consistent with enrichment of the PAHdegrading genus Pseudomonae.In contrast,sand did not enhance biological activity compared to media-free systems.Naphthalene strongly influenced microbial community composition at the species level in all treatments except organoclay,which promoted biological signatures commonly associated with impeding degradation activity.Data overall suggest that adsorptive capping materials can both promote(PAC)and inhibit(organoclay)bioactivity in the surficial layer of caps,indicating that media selection is critical to the design of bioactive capping systems.     

Nitrate Removal Rates in a 15-Year-Old Permeable Reactive Barrier Treating Septic System Nitrate

Permeable reactive barriers (PRBs) have gained popularity in recent years as a low-cost method for ground water remediation. However, their cost advantage usually requires that these barriers remain maintenance free for a number of years after installation. In this study, sediment cores were retrieved from a pilot-scale PRB consisting of a sand and wood particle (sawdust) mixture that has been in continuous operation for 15 years treating nitrate from a septic system plume in southern Ontario (Long Point site). Reaction rates for the 15-year-old media were measured in dynamic flow column tests and were compared to rates measured in year 1 using the same reactive mixture. Nitrate removal rates in the 15-year-old media varied, as expected, with temperature in the range of 0.22 to 1.1 mg N/L/d at 6 °C to 10 °C to 3.5 to 6.0 mg N/L/d at 20 °C to 22 °C. The latter rates remained within about 50% of the year 1 rates (10.2 ± 2.7 mg N/L/d at 22 °C). Near the end of the year 15 column test, media particles >0.5 mm in diameter, containing most of the wood particles, were removed from the reactive media by sieving. Nitrate removal subsequently declined by about 80%, indicating that the wood particles were the principal energy source for denitrification. This example shows that some denitrifying PRBs can remain maintenance free and be adequately reactive for decades.     

An experimental investigation of nitrogen gas produced during denitrification

In situ denitrification relies on indigenous microorganisms to reduce nitrate to N(2) gas. However, when initial nitrate concentrations are large, produced gas volumes also can be very large, potentially resulting in reduced water saturation and hydraulic conductivity in the treatment zone. In this study, we investigated the fate of N(2) and other gases produced during denitrification in a laboratory flow cell containing packed sediment. Denitrifying activity was stimulated by additions of nitrate and ethanol. Microbial activity was monitored by measuring nitrate, nitrite, and ethanol concentrations; gas saturations were measured during the experiment using a gamma imaging system. Biomass was measured using phospholipid fatty acid analysis of sediment samples. Bioenergetic calculations calibrated to measured nitrate consumed and biomass produced predicted that 1.2 L N(2) gas/L water should have been produced following the addition of 100 mM nitrate. However, the maximum measured gas saturation was only 23%, indicating substantial gas loss from the sediment pack. Temporal gamma images and visual observations confirm that small gas bubbles formed in the sediment pack coalesced into larger bubbles and migrated upward through gas-filled channels to the sediment pack surface. Although gas saturations increased, there was no significant change in sediment pack hydraulic conductivity. These results suggest that in permeable reactive barriers used for in situ denitrification, gas production will not necessarily lead to unlimited gas accumulation in the pore space and that the effects of gas production on water saturation and hydraulic conductivity may be relatively minor.     

Denitrifying bacteria and hydrogeochemistry in a natural wetland adjacent to farmlands in Chiba,Japan

This study combined bacterial incubation and hydrogeochemical methods to investigate denitrification in the surface water, top soil (0–20 cm), and shallow groundwater of the Ochi wetland in Japan. Surface water was rich in nitrate (40 mg/l) and denitrifying bacteria (700 per ml). Three functional zones in the wetland were identified in the top soil and shallow groundwater. In the upstream portion of the wetland (Zone I), the counts of denitrifying bacteria in top soil increased from 5200 to 14 970 per ml and nitrate decreased from 25·4 to 1·8 mg/l. Organic carbon concentrations decreased as sulfate increased from 4·0 to 9·6 mg/l in this zone. In the middle‐stream of the wetland (Zone II), all concentrations of major anions, iron, organic carbon, and total nitrogen content in top soil were relatively constant, but the counts of denitrifying bacteria increased up to 70 200 per ml. In the downstream portion of the wetland (Zone III), complete removal of nitrate resulted in sharp reduction of counts of denitrifying bacteria. Correspondingly, dissolved oxygen (DO), organic carbon, and total nitrogen increased in this zone. Counts of denitrifying bacteria were lower in shallow groundwater than in top soil; nitrate concentrations in shallow groundwater were also very low in this zone. DO and the oxidation/reduction potential data suggest that groundwater flows to the surface along an extended flow path, thus providing nitrate for the denitrifying community. Copyright © 2011 John Wiley & Sons, Ltd.     

The use of woods-run chips in filter socks to control erosion and sedimentation during petroleum development in the Appalachian Basin

Filter socks frequently are used for erosion and sediment perimeter control during oil and gas development activities in the Appalachian Basin of the United States. Regulations specify the use of composted wood material for sock construction. This specification, as opposed to non-composted or fresh wood chips (woods-run), has created inefficiencies during well site construction. Rather than use fresh wood chips created during site construction, composted chips must be procured and used as filter sock media for erosion and sedimentation mitigation. If woods-run chips could be used as filter sock media instead of composted chips, there could be a significant reduction in energy/capital costs, truck traffic, and disposal costs. The primary objective of this research project was to compare the effectiveness of woods-run material versus traditionally composted wood chips in controlling sediment transport as well as other chemical and physical parameters in a laboratory setting. No significant differences in pH (5.96 versus 6.02) or conductivity (0.029 dS/m versus 0.035 dS/m) were found in sediment laden water filtered through woods-run versus composted chips, respectively. However, chip particle sizes were outside the allowable limits for composted sock media, and moisture content also was outside the specified limits for woods-run chips. Nitrate (NO₃) concentrations were significantly higher in woods-run, while phosphorus (P) and potassium (K) concentrations were greater in composted chips; however none of the N,P, or K concentrations were above the regulatory requirements. Finally, no difference in the filtering efficiency or time was found between woods-run and composted material. The laboratory results indicate that current regulations allowing the use of woods-run chips in all but the highest quality watersheds is justified.     

Estimating the influence of increased nitrate loads from wastewater on phosphorus mobility in river sediments

Research on the sediment‐surface water transition zone in three study site regions, different in hydrological conditions, was conducted to estimate to which extent nitrate in surface water can contribute to riverbed sediment oxidation and thus prevent release of sediment phosphorus to surface water. Consequently, the Du tch Flow Model (DUFLOW) based water quality model “Spreewald” and results from the emission model “ Mo delling N utrient E missions in Ri ver S ystems” (MONERIS) were used to estimate to which extent wastewater treatment plants (WWTPs) could contribute to the NO₃^– concentration in surface waters if they were operated without denitrification. It is demonstrated that an effective phosphorus retention in sediments by means of surface water NO₃^– is possible only under specific conditions, i. e. (i) a sufficient supply of surface water to the sediment by advective fluxes, (ii) a sufficient amount of sediment iron to provide phosphorus binding sites in the case of sediment oxidation, (iii) a redox system not leading to a rapid NO₃^– and FeOOH depletion and to phosphorus release from organic pools by high microbial activities. Model results show that in‐stream denitrification processes counteract a significant increase of NO₃^– surface water concentrations from WWTPs operated without denitrification during summer, when eutrophication risk through phosphorus is highest. The increase of NO₃^– surface water concentrations in winter due to decreased denitrification in the surface water is of minor relevance for phosphorus release from sediments.     

Distribution, source and evolution of nitrate in a glacial till of southern Alberta, Canada

This paper addresses the distribution, origin and controls upon nitrate in a 30-km² area of the Interior Great Plains Region of southern Alberta, Canada. High concentrations of nitrate (> 100 mg l⁻¹ NO⁻₃-N) occurred in several isolated enclaves below the water table in brown weathered till. Nitrate concentrations of over 300 mg l⁻¹-N were encountered in groundwater samples collected from these enclaves. Low nitrate concentrations (< 1.1 mg l⁻¹ NO⁻₃-N) were also encountered in the weathered till upgradient and downgradient of the nitrate enclaves. Groundwater samples collected from the underlying grey nonweathered till and bedrock had NO⁻₃-N concentrations of < 1.1 mg l⁻¹.

Through the application of geochemical (NO⁻₃-N and NH⁺₄-N) studies, environmental isotope studies (tritium), microbial analyses (nitrifiers) and laboratory experiments, it was shown that the high nitrates found in the weathered till are the result of the oxidation of ammonium present within the tills. It is postulated that this oxidation occurred during the Holocene epoch when water tables were much lower than present-day levels (5–18 m, and 2 m below ground, respectively).

Through the use of Eh measurements, the enumeration of denitrifying bacteria and laboratory experiments, the potential for denitrification was shown to exist below the present-day water table in the weathered till as well as in the nonweathered till and bedrock. Isotopic data showed that less denitrification may be occurring within the nitrate enclaves than in adjacent downgradient areas.     

Ethanol-Stimulated Bioremediation of Nitrate-Contaminated Ground Water

Extensive characterization of a nitrate-contaminated site at a Canadian airport revealed that natural attenuation of the plume was limited due to aerobic conditions. However, nitrate removal rates as high as 1.4 mg-N/(L/day) were observed in batch tests carried out under denitrifying conditions with an added carbon source. On the basis of these results, a field denitrification pilot test using a setup of vertical withdrawal and injection wells was carried out. Ethanol was used as a carbon source to stimulate the growth and activity of indigenous denitrifying bacterial populations. Denitrification rates of up to 1.2 mg-N/(L/day) were achieved during the test. The test confirmed the feasibility of the technology, which uses the indigenous bacterial populations for denitrification and transforms the aquifer into a subsurface bioreactor.     

Direct measurement of dissolved N2 and denitrification along a subtropical river-estuary gradient,China

The spatial pattern and seasonal variation of denitrification were investigated during 2010–2011 in the Jiulong River Estuary (JRE) in southeast China. Dissolved N₂ was directly measured by changes in the N₂:Ar ratio. The results showed that excess dissolved N₂ ranged from ?9.9 to 76.4 μmol L^?1. Tidal mixing leads to a seaward decline of dissolved gaseous concentrations and water–air fluxes along the river-estuary gradient. Denitrification at freshwater sites varied between seasons, associated with changes in N input and water temperature. The denitrification process was controlled by the nitrate level at freshwater sites, and the excess dissolved N₂ observed at the tidal zone largely originated from upstream water transport. Compared to other estuaries, JRE has a relative low gaseous removal efficiency (E_d = 12% of [DIN]; annual N removal = 24% of DIN load), a fact ascribed to strong tidal mixing, coarse-textured sediment with shallow depth before bedrock and high riverine DIN input.     

不同生态处理方法对黑臭河道底泥细菌多样性与群落结构的影响

底泥细菌代谢是城市河道底泥代谢物的主要来源,最终决定城市河道的生态状况.本文研究了黑臭河道底泥经添加硝酸钙、生物促生剂和种植沉水植物处理后底泥中细菌群落结构的响应,以期为城市黑臭河道细菌群落的改善和综合治理提供理论依据.实验结果表明:经过不同生态处理后,上覆水中,添加硝酸钙组总氮(TN)含量显著高于对照组,添加生物促生剂组溶解氧浓度显著高于对照组.沉积物中,所有处理组的氧化还原电位值(ORP)均显著高于对照组,种植沉水植物组和添加硝酸钙组TN含量均显著低于对照组,沉积物理化性质得到一定改善.对不同生态处理组底泥细菌群落的研究发现,处理组底泥细菌群落产生了较大变化,且不同处理组细菌群落变化不同,生物促生剂组底泥中细菌的Sobs指数和Chao 1指数显著高于对照组和硝酸钙组,且生物促生剂组Shannon指数和PD指数显著高于硝酸钙组.Proteobacteria(Deltaproteobacteria、Betaproteobacteria、Gammaproteobacteria)、Chloroflexi、Firmicutes、Bacteroidetes和Spirochaetae是各实验组的主要优势菌门;非度量多维尺度分析表明:硝酸钙和生物促生剂的投加可明显改变底泥细菌群落结构组成.在属水平上,uncultured_Anaerolineaceae、Ferribacterium、uncultured_Xanthomonadales_Incertae_Sedis是导致底泥细菌群落发生变化的主要菌属.冗余分析结果表明,底泥ORP的变化是驱动细菌群落结构变化的关键环境因素.     

A simple method for the determination of ionic diffusion coefficients in flooded soils

Soil cores from river marginal wetlands from the Torridge and Severn catchments in the UK were collected to study rates of soil denitrification at different sites and at two stations (levee and backplain depression) at the river margin. Half the cores were sterilized prior to flooding to destroy the denitrifying bacteria. After flooding and equilibration, monitoring the concentration of amended nitrate in the supernatant of the sterile cores over a period of 7 days provided a simple procedure for the estimation of the diffusion coefficient of the nitrate ion in the flooded soils. An expression was developed that permitted this diffusion coefficient to be extracted from the slope of a plot of supernatant concentration versus (time)^1/2. The values obtained, at 15 °C, varied from 2·4 to 6·8 × 10^?10m²s^?1. Sterile cores are usually treated as controls in denitrification experiments; this work develops a procedure whereby they may yield useful soil process information. Copyright © 2001 John Wiley & Sons, Ltd.     

Root-associated biofilms of Eichhornia heterosperma Alexander, 1939 contribute to the remediation of the tropical reservoir Porce II,Colombia

Two key factors were identified that enhance remediation of a hypereutrophic reservoir colonised by Eichhornia heterosperma Alexander, 1939. These factors are the high abundance of the microbial community in root-associated biofilms and their high extracellular enzyme activity (EEA). The capacity of macrophytes for nutrients removal has been widely acknowledged. However, there has been little discussion on the role of root-associated biofilms in enhancing phytoremediation. We determined nutrient levels across the reservoir quarterly during two years. We assessed the structure of the microbial community in water, root-associated biofilms, and sediments along with their phosphatase and β-glucosidase activities. We hypothesised that reservoir remediation is enhanced by increased nutrient remineralisation and bioavailability, arising from EEA in root-associated biofilms attached to E. heterosperma. Sedimentation removed 51% of the total nitrogen (TN) and 85% of the total phosphorus (TP) external load. E. heterosperma and its root-associated biofilms removed extra 8% TN and 7% TP. The abundance of the microbial community in root-associated biofilms was generally higher than in water and sediment, being dominated by Alphaproteobacteria and Betaproteobacteria. The EEA in root-associated biofilms ranged 117−1760 μmol g⁻¹ wet weight h⁻¹ for phosphatase and 107−676 μmol g⁻¹ wet weight h⁻¹ for β-glucosidase, indicating high mineralisation rates. These results showed that the microbial community in root-associated biofilms favours reservoir remediation by supplying mineralised nutrients to algae and macrophytes, but the permanent introduction of high nutrient loads exceeds the reservoir capacity for remediation. Improving the trophic state of the reservoir requires thus long-term strategies at basin scale for reducing the nutrient loads.     

Seasonal variation in di-nitrogen fluxes and associated processes (denitrification, anammox and nitrogen fixation) in sediment subject to shellfish farming influences

Seasonal patterns of di-nitrogen fluxes together with denitrification, anammox, and N-fixation rates were studied in sediment in an area subject to strong human pressure via waste water, tributaries and shellfish farming in the Mediterranean Sea (Carteau Cove, NW area of the Gulf of Lion). Ammonium concentration demonstrated no seasonal variation, however, a large increase in its concentration was observed over a 10 years period due to intense biodeposition of organic matter. In contrast, nitrate concentration demonstrated no seasonal or long-term (10 years) variation. The main processes affecting di-nitrogen flux magnitudes were denitrification and N-fixation. Anammox was only detected occasionally, nevertheless it represented at times up to 39% of the N₂-flux. Nitrate reducing processes were variable and denitrification showed a 20-fold increase over the past 10 years and might actually have reached its potential maximal activity. Rates of N₂ production (denitrification and anammox) were generally higher than those of N-fixation, leading to elimination of nitrogen from the ecosystem.     

Biogeographical distribution and diversity of bacterial and archaeal communities within highly polluted anoxic marine sediments from the marmara sea

Physicochemical and microbiological characterization of anoxic sediments taken from seven highly polluted sites of the Marmara Sea was carried out. The 16S rRNA based microbial community structure analyses were performed using domain-specific PCR followed by denaturant gradient gel electrophoresis (DGGE) and sequencing of characteristic bands. The results showed that the microbial communities in these sediments were diverse and evenly distributed. Relating the prokaryotic and geochemical variables through statistical tools revealed that the microbial diversity in the sediments significantly related to depth, and S, Mn and Fe content of the sediments. Fermentative bacteria, denitrifying bacteria and hydrogenotrophic methanogens were dominant whereas sulfate reducing bacteria were absent in the DGGE patterns. This unusual microbial community structure implied that the newly discovered anaerobic methane oxidation coupled to denitrification process may occur in these subseafloor environments.     

太湖贡湖湾人工湖滨带水生植物恢复及其富营养化控制

以太湖贡湖湾人工湖滨带为对象,研究湖滨水生植物修复过程及其富营养化控制效果.人工湖滨区域内的消浪带、岸上护坡措施为水生植物修复提供了良好的生境条件,形成了包括荇菜（Nymphoides peltatum（Gmel.）Kuntze）、睡莲（Nymphaea tetragona Georgi）、菱（Trapa bispinosa Roxb.）为主的浮叶植物群落,以及以黑藻（Hydrilla verticillata（Linn.f.）Royle）、狐尾藻（Myriophyllum verticillatum L.）、小眼子菜（Potamogeton pusillus L.）、竹叶眼子菜（Potamogeton malaianus）为主的沉水植物群落.通过设置研究区、对照区,持续监测溶解氧、总氮、总磷、氨氮、叶绿素a浓度等水体指标,烧失量、氮含量、磷含量等沉积物指标,水生植物生物量、覆盖度,浮游藻类等指标.不同时期、不同区域间的时空分布显示：随着水生植物的恢复,水体营养状态指数（TLI）、沉积物生物生产力指数（BPI）显著下降,水体透明度显著提升;较高浓度的总氮（>3.0 mg/L）、氨氮（>0.6 mg/L）环境不利于浮叶植物的生长,沉水植物对其则表现出更好的适应性,同时水生植物在成长过程中直接从水体/沉积物中吸收氮;颤藻（Cyanophyta oscillatoria）、直裂藻（Cyanophyta merismopedia）等浮游藻类吸收了水体磷,水生植物利用了沉积物磷,共同缓解了磷在湖滨区域的累计.总结以上,湖滨带的水文水质条件可以影响水生植物群落结构,进而决定氮、磷的控制效果,所以在湖滨带修复中构建合适的生境条件是水生植物发挥氮磷控制效果的重要前提.水生植物在恢复过程中对浮游藻类群落结构的影响是显著的,并且以此影响到湖滨水体中磷的分布.     

Monte Carlo Simulations as a Decision Support to Interpret δ15N Values of Nitrate in Groundwater

Intense farming is often associated with the excessive use of manure or fertilizers and the subsequent deterioration of the groundwater quality in many aquifers worldwide. Stable isotopes of dissolved nitrate (δ¹⁵N and δ¹⁸O) are widely used to determine sources of nitrate contamination and denitrification processes in groundwater but are often difficult to interpret. Thus, Monte Carlo simulations were carried out for a site in lower Bavaria, Germany, in order to explain δ¹⁵N observations in a porous groundwater system with two aquifers, the main aquifer (MA) and several smaller perched aquifers (PA). For evaluating potential contributions, frequency distributions of δ¹⁵N were simulated deriving from (I) the mixing of different nitrate sources, related to land use, as input to groundwater, combined with (II) transport of nitrate in groundwater and (III) microbial denitrification. Simulation results indicate a source-driven isotopic shift to heavier δ¹⁵N values of nitrate in groundwater, which may be explained by land use changes toward a more intensified agriculture releasing high amounts of manure. Microbial denitrification may play a role in the PA, with simulated δ¹⁵N distributions close to the observations. Denitrification processes are however unlikely for the MA, as reasonable simulation curve fits for such a scenario were obtained predominantly for unrealistic portions of nitrate sources and related land use. The applied approach can be used to qualitatively and quantitatively evaluate the influence of different potential contributions, which might mask each other due to overlapping δ¹⁵N ranges, and it can support the estimation of nitrate input related to land use.     

Depth-related influences on biodegradation rates of phenanthrene in polluted marine sediments of Puget Sound, WA

A whole-core injection method was used to determine depth-related rates of microbial mineralization of (14)C-phenanthrene added to both contaminated and clean marine sediments of Puget Sound, WA. For 26-day incubations under micro-aerobic conditions, conversions of (14)C-phenanthrene to (14)CO(2) in heavily PAH-contaminated sediments from two sites in Eagle Harbor were much higher (up to 30%) than those in clean sediments from nearby Blakely Harbor (<3%). The averaged (14)C-phenanthrene degradation rates in the surface sediment horizons (0-3 cm) were more rapid (2-3 times) than in the deeper sediment horizons examined (>6 cm), especially in the most PAH polluted EH9 site. Differences in mineralization were associated with properties of the sediments as a function of sediment depth, including grain-size distribution, PAH concentration, total organic matter and total bacterial abundance. When strictly anaerobic incubations (in N(2)/H(2)/CO(2) atmosphere) were used, the phenanthrene biodegradation rates at all sediment depths were two times slower than under micro-aerobic conditions, with methanogenesis observed after 24 days. The main rate-limiting factor for phenanthrene degradation under anaerobic conditions appeared to be the availability of suitable electron acceptors. Addition of calcium sulfate enhanced the first order rate coefficient (k(1) increased from 0.003 to 0.006 day(-1)), whereas addition of soluble nitrate, even at very low concentration (<0.5 mM), inhibited mineralization. Long-term storage of heavily polluted Eagle Harbor sediment as intact cores under micro-aerobic conditions also appeared to enhance anaerobic biodegradation rates (k(1) up to 0.11 day(-1)).     

Nitrifying and Denitrifying Bacteria in Epiphytic Communities of Submerged Macrophytes in a Treated Sewage Channel

A quantification of nitrifying and denitrifying bacteria present in different compartments (water, sediments, submerged macrophytes) of a treated sewage channel was made to estimate their influence on the nitrogen balance and to assess the significance of macrophytes for nitrification and nitrogen conversions in general. Considerable numbers of autotrophic and heterotrophic nitrifying and denitrifiying bacteria were found to be present in the epiphytic communities of different species of submerged macrophytes of a treated sewage channel. Comparing the influence of the different compartments on total stream nitrification and denitrification it could be concluded that dense beds of submerged macrophytes particularly positively influence nitrification. Epiphytic nitrifiers were estimated to be as important for the total nitrification as nitrifiers in the sediment. Denitrification was mainly taking place in the sediment. The influence of the suspended nitrifiers and denitrifiers on the nitrogen balance was assumed to be negligible.     

太湖富营养化湖区秋季水体和沉积物中硝化微生物分布特征及控制因素

微生物参与下的氮循环是富营养化湖泊十分重要的生物地球化学循环过程.采用基于amoA功能基因和16S rRNA基因的荧光定量PCR、PCR-DGGE与高通量测序等分子生物学技术,调查秋季太湖不同水体和表层沉积物中氨氧化古菌(AOA)、氨氧化细菌(AOB)和亚硝酸盐氧化菌(NOB)群落丰度和组成,探讨影响硝化微生物分布的关键环境因子.结果表明,中度富营养化的梅梁湾湖区水体表层、中层和底层水样和表层底泥中AOA amoA基因的丰度分别低于轻度富营养化的湖心区,而不同层水样中AOB amoA基因的丰度分别高于湖心区.梅梁湾湖区和湖心区水样中AOA群落组成基本相似,2个湖区表层沉积物样品中AOA群落组成亦基本相似,水体中AOA群落组成与表层沉积物中AOA群落组成有差异,AOA群落丰度显著受硝态氮、pH和DO影响;表层沉积物中AOB群落丰度有明显差异且显著受总氮含量影响,表层沉积物中NOB群落丰度也有明显差异且显著受亚硝态氮含量影响.太湖梅梁湾湖区和湖心区水体与表层沉积物AOA群落包括Nitrosopumilium和Nitrosotalea两大属;表层沉积物AOB群落主要包括亚硝化单胞菌(Nitrosomonas)和亚硝化螺菌(Nitrosospira)两大属,NOB群落主要包括硝化刺菌(Nitrospina)和硝化螺菌(Nitrospira)两大属,其中硝化螺菌属是淡水湖泊中比较少见的亚硝酸盐氧化菌.影响太湖水体和沉积物中AOA和AOB丰度的最主要环境因子为总氮、总磷与铵态氮.研究表明典型富营养指标(总氮、总磷、铵态氮、硝态氮和硝态氮等)是影响太湖梅梁湾和湖心区水体和沉积物中AOA或AOB丰度以及硝化微生物群落丰度的重要因素.     

Spatial differences in denitrification and bacterial community structure of streams: relationships with environmental conditions

In streams, benthic bacterial communities are integral to multiple aspects of ecosystem function, including carbon and nitrogen cycles. Variation both in terms of bacterial community structure (based on taxonomic and/or functional genes) and function can reveal potential drivers of spatiotemporal patterns in stream processes. In this study, the abundance and diversity of 16S rRNA genes and abundance of nosZ genes, encoding for nitrous oxide reductase, were related to denitrification and environmental conditions. Denitrification rates varied among the three streams examined, and within a given stream there were significant longitudinal differences. Likewise, bacterial community structure based on analysis of the 16S rRNA gene also differed significantly among streams. However, variation in denitrification rate was not well correlated with environmental or biological variables measured. In addition, relatively large numbers of denitrifiers occurred when denitrification rates were low. In conclusion, although the streams differed in environmental conditions as well as bacterial community structure, these differences did not explain much of the spatial variation in denitrification rates.