Simultaneous Monitoring of Phosphine and of Phosphorus Species in Taihu Lake Sediments and Phosphine Emission from Lake Sediments

Phosphine (PH₃) was monitored in the Taihu Lake in China by a GC/NPD method, coupled with cryo-trapping enrichment technology. Results showed that PH₃ was universally detected in sediments, lake water and atmosphere of the Taihu Lake area. Total phosphorus (TP_s) and fractions of different phosphorus species in lake sediments were separately measured as dissolved phosphate (DP), phosphorus bound to aluminum (Al-P), iron (Fe-P) and calcium (Ca-P), occluded phosphorus (OP), and organic phosphorus (Org-P) by sequential chemical extraction. High PH₃ levels were correlated with high TP_s values in sediments and with eutrophication at different sites. In addition, a positive linear correlation equation was obtained between the concentrations of PH₃ in lake sediments and of the phosphorus fractions. The resulting multiple linear regression equation is PH₃ = −165 + 63.3 DP + 0.736 Al-P + 2.33 Ca-P + 2.29 Org-P. The flux of PH₃ across the sediment–water interface was estimated from sediment core incubation in May and October 2002. The annual average sediment–water flux of PH₃ was estimated at ca. 0.0138±0.005 pg dm⁻² h⁻¹, the average yearly emission value of PH₃ from Taihu Lake sediments to water was calculated to be 28.3±10.2 g year⁻¹, which causes a water PH₃ concentration of up to 0.178±0.064 pmol dm⁻³. The real importance of PH₃ could be higher, because PH₃ could be consumed in the oxic sediment–water boundary layer and in the water column. Spatial and temporal distributions of total phosphorus (TP_w) and chlorophyll a (Chl-a) in the water column of Taihu Lake were measured over the study period. Higher water PH₃ has also been found where the TP_w content was high. Similarly, high Chl-a was consistent with higher water PH₃. Positive relationships between PH₃ and TP_w (average R² = 0.47±0.26) and Chl-a (average R² = 0.23±0.31) were observed in Taihu Lake water.     

Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading

Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) loading from lake sediments can account for a substantial portion of the total P load in eutrophic, and some mesotrophic, lakes. Laboratory determination of P release rates from sediment cores is one approach for determining the role of internal P loading and guiding management decisions. Two principal alternatives to experimental determination of sediment P release exist for estimating internal load: in situ measurements of changes in hypolimnetic P over time and P mass balance. The experimental approach using laboratory-based sediment incubations to quantify internal P load is a direct method, making it a valuable tool for lake management and restoration.Laboratory incubations of sediment cores can help determine the relative importance of internal vs. external P loads, as well as be used to answer a variety of lake management and research questions. We illustrate the use of sediment core incubations to assess the effectiveness of an aluminum sulfate (alum) treatment for reducing sediment P release. Other research questions that can be investigated using this approach include the effects of sediment resuspension and bioturbation on P release.The approach also has limitations. Assumptions must be made with respect to: extrapolating results from sediment cores to the entire lake; deciding over what time periods to measure nutrient release; and addressing possible core tube artifacts. A comprehensive dissolved oxygen monitoring strategy to assess temporal and spatial redox status in the lake provides greater confidence in annual P loads estimated from sediment core incubations.     

Excessive Phosphorus Loading to Dal Lake,India: Implications for Managing Shallow Eutrophic Lakes in Urbanized Watersheds

Extensive watershed development has resulted in excessive total phosphorus (TP) loads to Dal Lake, a high altitude Himalayan lake known for its tourism and economic potential. External and internal TP loads of 5 and ∼1 g m^–2 yr^–1, respectively, were estimated for the lake. These loading rates are high in relation to the lake's critical tolerance range of 0.1–0.2 g m^–2 yr^–1, and, over time, have resulted in severe eutrophication in view of extremely high macrophyte biomass (average = 3.2 kg m^–2‐fresh weight) and bottom sediment enrichment (79 tons of TP reserves which contribute 88% of the annual TP budget). This study emphasizes the importance of external TP load reduction as a primary management objective to counteract internal TP loading and P storage within bottom sediments resulting from historic anthropogenic loads. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microbial Populations Involved in Cycling of Dimethyl Sulfide and Methanethiol in Freshwater Sediments

Although several microorganisms that produce and degrade methanethiol (MT) and dimethyl sulfide (DMS) have been isolated from various habitats, little is known about the numbers of these microorganisms in situ. This study reports on the identification and quantification of microorganisms involved in the cycling of MT and DMS in freshwater sediments. Sediment incubation studies revealed that the formation of MT and DMS is well balanced with their degradation. MT formation depends on the concentrations of both sulfide and methyl group-donating compounds. A most-probable number (MPN) dilution series with syringate as the growth substrate showed that methylation of sulfide with methyl groups derived from syringate is a commonly occurring process in situ. MT appeared to be primarily degraded by obligately methylotrophic methanogens, which were found in the highest positive dilutions on DMS and mixed substrates (methanol, trimethylamine [TMA], and DMS). Amplified ribosomal DNA restriction analysis (ARDRA) and 16S rRNA gene sequence analysis of the total DNA isolated from the sediments and of the DNA isolated from the highest positive dilutions of the MPN series (mixed substrates) revealed that the methanogens that are responsible for the degradation of MT, DMS, methanol, and TMA in situ are all phylogenetically closely related to Methanomethylovorans hollandica. This was confirmed by sequence analysis of the product obtained from a nested PCR developed for the selective amplification of the 16S rRNA gene from M. hollandica. The data from sediment incubation experiments, MPN series, and molecular-genetics detection correlated well and provide convincing evidence for the suggested mechanisms for MT and DMS cycling and the common presence of the DMS-degrading methanogen M. hollandica in freshwater sediments.     

Bag Experiments on the Effect of Phosphorus and Base Additions on the Algal Biomass and Species Composition of an Acid Lake

Bag experiments were conducted to determine the effect of neutralization and phosphorus additions on phytoplankton in a lake acidified by mine drainage. Neutralization and phosphorus additions caused a lag of several days before algal growth occurred.     

Functions of Calcium-bound Phosphorus in Relation to Characteristics of Phosphorus Releasing Bacteria in Sediment of a Chinese Shallow Lake (Lake Wabu)

Sediment phosphorus (P) release accelerates lake eutrophication, while retention capacity and release potential of different P fractions, calcium-bound P (CaCO₃～P) in particular, still remains unclear. Fractionation and sorption behaviors of phosphorus were studied in sediment of a Chinese shallow lake (Lake Wabu) and two inflowing rivers from December 2011 to December 2012. Abundance of P releasing bacteria was analyzed, and their main species were isolated using a culture-dependent method and identified by their 16S rDNA sequences. CaCO₃～P release abilities of these bacteria were also tested. In sediments of both the lake and rivers studied, the rank order of the different P extracts was CaCO₃～P > iron-bound P > acid-soluble organic P > hot NaOH-extractable organic P. At the same time, CaCO₃～P content and equilibrium P concentration (EPC₀) values in river sediments were significantly higher than those in the lake. Additionally, EPC₀ changes non-monotonically with increasing CaCO₃～P content, forming a V-shaped curve, with the lowest EPC₀ at an intermediate CaCO₃～P content (around 180 mg kg^?1). Below this threshold, CaCO₃～P was a component strengthening P retention; moreover, CaCO₃～P became an active species responsible for P release. Noticeably, between the two parts divided by this threshold, the differences in abundance of inorganic phosphorus solubilizing bacteria (IPB) and organic phosphorus mineralizing bacteria (OPB) were insignificant and the dominant IPB species clustered together. By contrast, OPB was distinguished from each other, whose dominant species isolated from the part with higher CaCO₃～P content, namely Novosphingobium sp., exhibited a stronger ability to solubilize CaCO₃～P. Shortly, with lower content, CaCO₃～P tends to stabilize P in sediment; while with higher content or under eutrophic condition, it shifted into P source, with some OPB species becoming the main factors to drive its release.     

Microbial Community Composition in Acid Mine Drainage Lake of Xiang Mountain Sulfide Mine in Anhui Province,China

Acid mine drainage (AMD) lake of Xiang Mountain in Anhui Province, China, was characterized by acidic waters (pH around 2.8) containing high concentrations of soluble metals and sulfate. To investigate the function and dynamics of this extreme ecosystem, four water samples were collected from the lake in the fall of 2010. The acidophilic community structure was analyzed by molecular approaches, and bacterial and archaeal clone libraries of 16S rRNA genes were constructed. In contrast to dominance of chemolithotrophic acidophiles in typical AMD environments, autotrophic iron/sulfur-oxidizing bacteria were detected in only one sample with low abundance. Unexpectedly, the Cyanobacteria group was the predominant in all four samples (54.9%?77%). Chemoheterotrophs Acidiphilium and Acidisphaera were also abundant. These two heterotrophic groups contain bacteriochlorophyll that can perform photosynthesis, an advantage to grow and survive in such oligotrophic acidic environments. Only two clone sequences related to Legionella (2.8% of the total clones) were recovered from one sample in sharp contrast to its higher abundance (12.7%) in the summer of 2009. All archaeal sequences were affiliated to the phylum Crenarchaeota. The results of statistical analysis suggested that the water chemistry of the AMD lake controlled microbial composition of the AMD ecosystem.     

Influence of Submerged Plants on Phosphorus Fractions and Profiles of Sediments in Gucheng Lake

To understand the effect of submerged macrophytes on P in sediment, P fractions in the surface sediments (0–20 cm) of Potamogeton crispus, Potamogeton maackianus and non-vegetated areas were investigated. In the submerged macrophytes areas, the concentrations of HCl-P, NaOH-P, IP, OP and BD-P were significantly lower than in the non-vegetated area. NH₄Cl-P did not differ significantly among areas.

In the submerged macrophyte distribution areas, TP was significantly correlated with IP and OP. However, in the non-vegetated area, TP was significantly correlated with NH₄Cl-P and OP. In all of the areas sampled, IP was the major phosphorus fraction in the sediments, which consists largely of NAOH-P and HCl-P. The decreasing order of P fractions was: IP > HCl-P > NaOH-P > OP > BD-P > NH₄Cl-P. These results show that submerged macrophytes can decrease the concentrations of all P fractions and imply that submerged macrophytes play a key role in the retention of P nutrients.     

Phosphorus Fractionation in Core Sediments from Haihe River Mainstream,China

Sediments from Haihe River mainstream, located in Xingjiaquan, Zhangjiazui, Tianjin, were collected and examined on the basis of P fractionation. SMT (standards, measurements and testing) procedure was adopted to investigate the changes in P concentration with depth in the core sediments collected from the different sampling sites of Haihe River mainstream. The relationships among different P fractions, such as exchangeable P (Ex-P), metal oxide bounded P (NaOH-P), organic matter and grain size, were also discussed. The results indicate that in both sites the rank order of P fractions was HCl-P > Organic P (OP) > NaOH-P > Ex-P in terms of their concentration. The Ex-P represented < 4% of the sediment total P, while the NaOH-P ranged 5–21%. The calcium bound phosphorus (HCl-P) showed considerable contribution (53–80%) to the sediment total P loads. Silt/clay sized sediments exhibited significantly higher concentrations of HCl-P and Ex-P in both sites. However, coarse-sand-sized sediments exhibited significantly higher concentrations of OP in both sites and NaOH-P in Xingjiaquan. Multivariate statistics were performed to identify the factors that influenced the sediment P.     

Species and Biogeochemical Cycles of Organic Phosphorus in Sediments From a River With Different Aquatic Plants Located in Huaihe River Watershed,China

The results of phosphorus fractionation in the sediments from a contaminated river containing different aquatic plants, analyzed by solution ³¹P-NMR for Organic Phosphorus, showed that the concentration of Inorganic Phosphorus dominated in all species and Organic Phosphorus accounted for over 20% of Total Phosphorus. In general, orthophosphate was dominant in all the sampling sites. The proportion of Organic Phosphorus accounting for the Total Phosphorus in the sediments with different plant decreased in the following order: Paspalum distichum > Typha orientalis > Hydrilla verticillata. Phosphorus-accumulation ability of Paspalum distichum was obviously stronger than Typha orientalis and Hydrilla verticillata. The Organic Phosphorus was in aquatic plants dominated by humic-associated P (Hu-P), which converted to Inorganic Ohosphorus more significantly in submerged plants than in emerged plants. The sediment dominated by Paspalum distichum abundantly accumulated Organic Phosphorus in the orthophosphate monoester fraction. The degradation and mineralization of orthophosphate monoester was the important source of high Inorganic Phosphorus concentration and net primary productivity in Suoxu River. The Organic Phosphorus derived from Typha orientalis and Hydrilla verticillata was dramatically converted to Inorganic Phosphorus when the environmental factors varied.     

Spatial Distribution of Biochemical Parameters Indicating Biomass and Community Composition of Microbial Assemblies In Estuarine Mud Flat Sediments

The spatial distribution of communities was examined in estuarine mud flat sediments by the biochemical analysis of the lipids and lipid components extracted from the sediments. Total phospholipid was used as a measure of total biomass, and fatty acids were used as indicators of community composition. Comparisons were made among 2- by 2-m (location) and 0.2- by 0.2-m (cluster) sampling plots by using a nested analysis of variance to design an optimal sampling strategy to define the microbial content of a large, relatively homogenous area. At two of the three stations, a 2- by 2-m plot was representative of the station, but 0.2- by 0.2-m areas were in no case representative of the station. The biomass measured by the extractable phospholipid and the total lipid palmitic acid showed excellent correlation with the fatty acid “signatures” characteristic of bacteria, but showed a lower correlation with the long-chain polyenoic fatty acids characteristic of the microfauna.     

滇池流域人工林群落结构及水土保持效益

以滇池流域5种主要人工林(柏木林、桉树林、银荆林、华山松林和云南松林)为研究对象,通过样方调查,分析群落结构特征,并构建了由植被、枯落物、土壤、地形4个因子组成的水土保持功能评价指标体系,在对所选取的8个指标进行标准化、确定权重的基础上,运用理想点综合评价方法评价其水土保持效益.结果表明:各人工林群落优势种重要值(Ⅳ)分别为:柏木89.69、桉树74.27、银荆96.35、华山松84.93、云南松65.65.桉树林、云南松林分层物种多样性表现为灌木层＞草本层＞乔木层,柏木林、银荆林和华山松林分层物种多样性表现为草本层＞灌木层＞乔木层.云南松林的群落总体物种多样性最高,华山松林和桉树林次之,柏木林较低,银荆林最低.各人工林水土保持效益依次为:云南松林＞华山松林＞柏木林＞桉树林＞银荆林,表明乡土树种作为水土保持林具有一定的优势.不同人工林在物种多样性及水土保持效益等方面存在明显差异,应根据立地条件选择适宜的造林树种及搭配方式,提升其生态功能,控制水土流失.     

Structural Stability,Microbial Biomass and Community Composition of Sediments Affected by the Hydric Dynamics of an Urban Stormwater Infiltration Basin

The sedimentary layer deposited at the surface of stormwater infiltration basins is highly organic and multicontaminated. It undergoes considerable moisture content fluctuations due to the drying and inundation cycles (called hydric dynamics) of these basins. Little is known about the microflora of the sediments and its dynamics; hence, the purpose of this study is to describe the physicochemical and biological characteristics of the sediments at different hydric statuses of the infiltration basin. Sediments were sampled at five time points following rain events and dry periods. They were characterized by physical (aggregation), chemical (nutrients and heavy metals), and biological (total, bacterial and fungal biomasses, and genotypic fingerprints of total bacterial and fungal communities) parameters. Data were processed using statistical analyses which indicated that heavy metal (1,841 μg/g dry weight (DW)) and organic matter (11%) remained stable through time. By contrast, aggregation, nutrient content (NH₄⁺, 53–717 μg/g DW), pH (6.9–7.4), and biological parameters were shown to vary with sediment water content and sediment biomass, and were higher consecutive to stormwater flows into the basin (up to 7 mg C/g DW) than during dry periods (0.6 mg C/g DW). Coinertia analysis revealed that the structure of the bacterial communities is driven by the hydric dynamics of the infiltration basin, although no such trend was found for fungal communities. Hydric dynamics more than rain events appear to be more relevant for explaining variations of aggregation, microbial biomass, and shift in the microbial community composition. We concluded that the hydric dynamics of stormwater infiltration basins greatly affects the structural stability of the sedimentary layer, the biomass of the microbial community living in it and its dynamics. The decrease in aggregation consecutive to rewetting probably enhances access to organic matter (OM), explaining the consecutive release of NH₄⁺, the bloom of the microbial biomass, and the change in structure of the bacterial community. These results open new perspectives for basin management since the risk of OM and pollutant transfer to the aquifer is greatly affected by alternating dry and flood periods.     

Deep Subsurface Microbial Biomass and Community Structure in Witwatersrand Basin Mines

The extreme environments of South Africa mines were investigated to determine microbial community structure and biomass in the deep subsurface. These community parameters were determined using phospholipid fatty acid (PLFA) technique. Air, water and rock samples were collected from several levels and shafts in eight different mines. Biomass estimates ranged over nine orders of magnitude. Biofilm samples exhibited the highest biomass with quantities ranging from 10 ³ to 10 ⁷ pmol PLFA g ^?1 . Rock samples had biomass ranging from 10 ³ to 10 ⁶ pmol PLFA g ^?1 . Mine service waters and rock fracture waters had biomass estimates ranging from 10 ⁰ to 10 ⁶ pmol PLFA L ^?1 . Air samples biomass values ranged from 10 ^?2 to 10 ⁰ pmol PLFA L ^?1 . The biomass estimates were similar to those estimates for other deep subsurface sites. Redundancy analysis of the PLFA profiles distinguished between the sample types, where signature lipid biomarkers for aerobic and anaerobic prokaryotes, sulfate-and metal-reducing bacteria were associated with biofilms. Rock samples were enriched in 18:1 ω 9 c , 18:2 ω 6, br17:1s and br18:1s, which are indicative of microeukaryotes and metal- reducing bacteria. Air samples were enriched with 22:0, 17:1, 18:1, and a polyunsaturated fatty acid. Service waters had monounsaturated fatty acids. Fracture waters contained i17:0 and 10Me18:0 which indicated gram-positive and other anaerobic bacteria. When the fracture and service water sample PLFA responses to changes in environmental parameters of temperature, pH, and anion concentrations were analyzed, service waters correlated with higher nitrate and sulfate concentrations and the PLFAs 18:1 ω 7 c and 16:1 ω 7 c . Dreifontein shaft 5 samples correlated with chloride concentrations and terminally branched saturated fatty acids and branched monounsaturated fatty acids. Kloof, Tau Tona, and Merriespruit fracture waters aligned with temperature and pH vectors and 18:0, 20:0 and 22:6 ω 3. The redundancy analysis provided a robust method to understand the PLFA responses to changes in environmental parameters.     

Quantifying Relationships Among Phosphorus, Agriculture, and Lake Depth at an Inter-Regional Scale

To date, studies examining the impact of agriculture on freshwater systems have been spatially confined (that is, single drainage basin or regional level). Across regions, there are considerable differences in a number of factors, including geology, catchment morphometry, and hydrology that affect water quality. Given this heterogeneity, it is unknown whether agricultural activities have a pervasive impact on lake trophic state across large spatial scales. To address this issue, we tested whether the proportion of agricultural land in a catchment (% Agr) could explain a significant portion of the variation in lake water quality at a broad inter-regional scale. As shallow, productive systems have been shown to be particularly susceptible to eutrophication, we further investigated how lake mean depth modulates the relationship between % Agr and lake total phosphorus (TP) concentration. We applied both traditional meta-analytic techniques and more sophisticated linear mixed-effects models to a dataset of 358 temperate lakes that spanned an extensive spatial gradient (5°E to 73°W) to address these issues. With meta-analytical techniques we detected an across-study correlation between TP and % Agr of 0.53 (one-tailed P-value = 0.021). The across-study correlation coefficient between TP and mean depth was substantially lower (r = −0.38; P = 0.057). With linear mixed-effects modeling, we detected among-study variability, which arises from differences in pre-impact (background) lake trophic state and in the relationship between lake mean depth and lake TP. To our knowledge, this is the first quantitative synthesis that defines the influence of agriculture on lake water quality at such a broad spatial scale. Syntheses such as these are required to define the global relationship between agricultural land-use and water quality.     

Transformation of Organic Matter by a Microbial Community in Sediments of Lake Baikal under Experimental Thermobaric Conditions of Protocatagenesis

Early diagenesis of organic matter in bottom sediments of Lake Baikal is a focus of many geochemical studies, because it is one of the few sites of petroleum formation in a nonmarine environment. Although Baikal is a rift lake and considered one of the prospective fields for deep biosphere investigations, the transformation processes of organic matter by microbial communities from deep bottom sediments and likely entering of the microorganisms from deep sediments into the near-surface sediments were not previously studied in Lake Baikal. The natural microbial community from near-surface sediments of the cold methane seep Goloustnoe (Southern Baikal Basin) was incubated with methane and the diatom Synedra acus at 80°C and 49.5 atm to simulate catagenesis. The 11-month incubation yielded the enrichment culture of viable thermophilic microorganisms. Their presence in low-temperature sediment layers may be indicative of their migration through fault zones together with gas-bearing fluids. After culturing, molecular biological methods allowed for the detection of both widespread microorganisms and unique clones whose phylogenetic status is currently unknown. The sediment after the experiment showed the formation of polycyclic aromatic hydrocarbon, retene. Retene can be either a conifer or algal biomarker, thus, interpretation of paleoclimate data is tenuous.     

Linking Microbial Community Structure to S,N and Fe Biogeochemical Cycling in the Hot Springs at the Tengchong Geothermal Fields,Southwest China

Sediment and water samples collected from one acidic and three alkaline high temperature hot springs at the Tengchong terrestrial geothermal field, Southwest China, were examined using mineralogical, geochemical, and molecular biological techniques. The mineralogical and geochemical analyses suggested that these hot springs contained relatively high concentrations of S, Fe and N chemical species. Specifically, the acidic water was rich in Fe²⁺, SO₄^2? and NH₄⁺, while the alkaline waters were high in NO₃^?, H₂S and S₂O₃^?. Analyses of 16S rRNA gene sequences showed their bacterial communities were dominated by phyla Aquificae, Cyanobacteria, Deinococci-Thermus, Firmicutes, Proteobacteria, and Thermodesulfobacteria, while the archaeal clone libraries were dominated by orders Desulfurococcales, Sulfolobales, and Thermoproteales. Potential S-, N- and Fe-metabolizing prokaryotes were present at a relatively high proportion, but with large differences in the diversity and metabolic functions of each sample. These findings provide implications for uncovering microbial functions in elemental biogeochemical cycles within the Tengchong geothermal environments: i). the distinct differences in abundance and diversity of microbial communities in geothermal sediments were related to different in situ physicochemical conditions; ii). the S-, N- and Fe-related prokaryotes would take advantage of the strong chemical disequilibria in the hot springs; and iii). in return, their metabolic activities could promote the transformation of the S, Fe and N chemical species, thereby forming the basis of biogeochemical cycles in the terrestrial geothermal environments.     

Vertical distribution and release characteristics of phosphorus forms in the sediments from the river inflow area of Dianchi Lake,China

Columnar sediment samples were collected from five representative river inflow areas of Dianchi Lake, China. The vertical distribution of each form of P were tested. Results showed that the concentration of TP in the sediments from areas A, B, C, D and E in the order of D > B > A > C > E, and the average concentration of D, B, A, C and E were 2991, 2064, 1308, 879, and 759 mg?kg^?1, respectively. The concentration of Ex-P, Fe/Al-P, Ca-P and Org-P all decreased with increasing depth. The release of Ex-P was significantly related to TP whereas the Fe/Al-P was not significantly related to TP in the samples from areas polluted by domestic sewage. However, the release of Ex-P and Fe/Al-P were both significantly related to TP in the samples from areas polluted by phosphate mining and phosphate fertilizer application. The results of equilibrium P concentration (EPC0) analysis showed that P in the sediments of areas A, D and E were the source of P in Dianchi Lake, and the P in the sediments of areas B and C were in relative equilibrium with the overlying water.     

Impact of Anthropogenic Organic Matter on the Distribution Patterns of Sediment Microbial Community from the Yangtze River,China

Abstract

How microbes respond to substantial and increasing anthropogenic disturbance remains an open question in river systems. We tested the hypothesis that the source and distribution of anthropogenic organic matter (OM) were significant factors affecting the spatial variation of the microbial community composition of the Yangtze River sediments. Bulk geochemical proxies and lignin phenols suggested a general decrease of terrestrial C3 plants or soil OM input from the middle to the lower reaches. Fecal sterols inferred higher sewage contamination levels in the middle reaches. Polycyclic aromatic hydrocarbons (PAHs) distribution indicated a dominant biomass and coal combustion signal in the middle reaches, whereas a mixed source including petroleum combustion in the lower reaches. Phylogenetic analysis revealed a large portion of Methanobacteria and Verrucomicrobia enriched in the middle reaches, whereas OM-degrading bacteria, including Flavobacteria, Acidobacteria, and Alphaproteobacteria were dominant in the lower reaches. Quantitative PCR analyses and multivariate analysis further demonstrated that sources and distribution of OM had combined effects in shaping alpha and beta-diversity of sediment microbial communities. Sewage discharge and incomplete OM combustion, respectively, were associated with Methylococcaceae, Chloroflexi, and Bacteroidetes groups. This study provides a foundation for further understanding of the river sediment microbial composition, considering the continued increase of anthropogenic influences.