Sagami River Research Articles

Near full-automation of COPMAN using a LabDroid enables high-throughput and sensitive detection of SARS-CoV-2 RNA in wastewater as a leading indicator

Wastewater-based epidemiology (WBE) is a promising tool to efficiently monitor COVID-19 prevalence in a community. For WBE community surveillance, automation of the viral RNA detection process is ideal. In the present study, we achieved near full-automation of a previously established method, COPMAN (COagulation and Proteolysis method using MAgnetic beads for detection of Nucleic acids in wastewater), which was then applied to detect SARS-CoV-2 in wastewater for half a year. The automation line employed the Maholo LabDroid and an automated-pipetting device to achieve a high-throughput sample-processing capability of 576 samples per week. SARS-CoV-2 RNA was quantified with the automated COPMAN using samples collected from two wastewater treatment plants in the Sagami River basin in Japan between 1 November 2021 and 24 May 2022, when the numbers of daily reported COVID-19 cases ranged from 0 to 130.3 per 100,000 inhabitants. The automated COPMAN detected SARS-CoV-2 RNA from 81 out of 132 samples at concentrations of up to 2.8 × 105 copies/L. These concentrations showed direct correlations with subsequently reported clinical cases (5–13 days later), as determined by Pearson's and Spearman's cross-correlation analyses. To compare the results, we also conducted testing with the EPISENS-S (Efficient and Practical virus Identification System with ENhanced Sensitivity for Solids, Ando et al., 2022), a previously reported detection method. SARS-CoV-2 RNA detected with EPISENS-S correlated with clinical cases only when using Spearman's method. Our automated COPMAN was shown to be an efficient method for timely and large-scale monitoring of viral RNA, making WBE more feasible for community surveillance.

The fine-scale genetic structure and dispersal ability of the mayfly Ecdyonurus yoshidae Takahashi (Ephemeroptera: Heptageniidae) in the Sagami River system, southern Kanto Region, Japan

• The Sagami River has its source at Lake Yamanaka near Mount Fuji in Japan. • We studied the genetic structure of Mayfly Ecdyonurus yoshidae . • Two haplogroups occur in the Sagami river. • One haplogroup spread throughout the river system. • Another haplogroup may have migrated from an adjacent catchment. Aquatic organisms frequently exhibit clear genetic structures over their distribution ranges. In a previous study, we showed that the mayfly Ecdyonurus yoshidae Takahashi also showed genetic delimitations in the Japanese archipelago. In this paper, we studied the dispersal and migration of this species using the fine-scale genetic structure and historical demographic dynamics in the Sagami River system using the DNA barcoding region mitochondrial cytochrome c oxidase subunit I gene sequence ( COI ). We detected two major haplogroups constructed from 44 distinct haplotypes in 226 specimens collected from 24 sampling sites. From the highest altitude of 530 m to the lowest of 7 m, the dominant haplotype was widespread throughout the rivers and the six tributaries and even spread to isolated microhabitats upstream. We did not observe genetic differentiation among the six tributaries and 24 sampling sites. Consequently, we estimated that the population occurring in the entire river system is maintained as a meta-population by suitable small-scale habitats. We found that E. yoshidae might be capable of crossing areas with unsuitable habitats, such as gorges and rapid streams. Furthermore, one haplogroup experienced population expansion—which affected the genetic structure across the Sagami River system—and another haplogroup might have migrated from an adjacent catchment.

COPMAN: A novel high-throughput and highly sensitive method to detect viral nucleic acids including SARS-CoV-2 RNA in wastewater

During the coronavirus disease 2019 (COVID-19) pandemic, wastewater-based epidemiology (WBE) attracted attention as an objective and comprehensive indicator of community infection that does not require individual inspection. Although several severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection methods from wastewater have been developed, there are obstacles to their social implementation. In this study, we developed the COPMAN (Coagulation and Proteolysis method using Magnetic beads for detection of Nucleic acids in wastewater), an automatable method that can concentrate and detect multiple types of viruses from a limited volume (∼10 mL) of wastewater. The COPMAN consists of a high basicity polyaluminum chloride (PAC) coagulation process, magnetic bead-based RNA purification, and RT-preamplification, followed by qPCR. A series of enzymes exhibiting a high tolerance to PCR inhibitors derived from wastewater was identified and employed in the molecular detection steps in the COPMAN. We compared the detectability of viral RNA from 10-mL samples of virus-spiked (heat-inactivated SARS-CoV-2 and intact RSV) or unspiked wastewater by the COPMAN and other methods (PEG-qPCR, UF-qPCR, and EPISENS-S). The COPMAN was the most efficient for detecting spiked viruses from wastewater, detecting the highest level of pepper mild mottle virus (PMMoV), a typical intrinsic virus in human stool, from wastewater samples. The COPMAN also successfully detected indigenous SARS-CoV-2 RNA from 12 samples of wastewater at concentrations of 2.2 × 104 to 5.4 × 105 copies/L, during initial stages of an infection wave in the right and the left bank of the Sagami River in Japan (0.65 to 11.45 daily reported cases per 100,000 people). These results indicate that the COPMAN is suitable for detection of multiple pathogens from small volume of wastewater in automated stations.

Pyroclastic dyke intruded into the Jurassic accretionary complex along the Sagami River, east of Mt. Otowa, Otsu City, Shiga Prefecture, Central Japan

Pyroclastic dyke intruded into the Jurassic accretionary complex along the Sagami River, east of Mt. Otowa, Otsu City, Shiga Prefecture, Central Japan

Elucidation of Phenomena Involving Cyanobacteria in Freshwater Ecosystem by Chemically Ecological Approach

Lakes Sagami and Tsukui are reservoirs constructed by connecting to the Sagami River. Because of eutrophication of the lakes, cyanobacteria have appeared every year. This review deals with phenomena related to occurrence of cyanobacteria that have been observed for 40 years since 1974 at the lakes. These 40 years of observations raised three interesting issues including the retention of cyanobacteria on their surfaces. These phenomena have been attributed to the usual factors, such as illuminance, nutrition and water temperature, but our research results suggested that they cannot be resolved without the introduction of another factor. We have attempted to elucidate various phenomena involving cyanobacteria in lake ecosystems by chemical ecological methods using volatile organic compounds (VOCs) produced by the cyanobacteria as indicators. One of the VOCs, β-cyclocitral, was significantly involved in the above phenomena, which was considered to be produced by the carotenoid cleavage dioxygenase (CCD) of the cyanobacteria. β-Cyclocitral was not produced in the two known CCDs, but two additional CCDs to Microcystis aeruginosa participated to produce the β-cyclocitral. These CCDs did not directly produce β-cyclocitral, but it was accumulated in cells as their precursors. The released β-cyclocitral underwent a Baeyer-Villiger-like oxidation. It was speculated that Microcystis activated the CCD genes through density stress and produced β-cyclocitral, which acted as an allelopathic substance. As a result, the number of cells of cyanobacteria decreased, and the resulting nitrogen and phosphorus were fed to the living cyanobacteria. It is postulated that this "quorum sensing" was functioning in the above-mentioned issues.

Food resource use by juveniles of the endangered sleeper Eleotris oxycephala in the Sagami River system, Japan

To ascertain the early food resource use of the endangered sleeper, Eleotris oxycephala, the food habits of juveniles were studied in a major stream (which received treated sewage discharge and had a low level of vegetation cover) and a tributary (which received little artificial inflow and had extensive vegetation cover) in the Sagami River system, eastern Japan in November 2015 (winter), May 2016 (spring), and August/September 2016 (summer). The stomach content compositions of 174 individuals and the stable isotope ratios of 30 individuals and their prey animals were investigated along with the species composition of prey animals in the environment. Various aquatic animals, including fish eggs, mollusks, crabs, palaemonid shrimps, atyid shrimps, isopods (asellids), chironomid larvae, and dragonfly larvae, were present in juvenile E. oxycephala stomach contents. In the tributary, they mainly preyed on atyid shrimps, which were abundant in the environment, with lower feeding intensity during winter season. In the major stream, throughout the year (including winter), they fed mainly on chironomid larvae, which were smaller and slower than atyid shrimps, and so easily caught, even by small recently recruited juveniles. There were abundant chironomid larvae in the major stream environment, where the water temperature seemed warmer and more eutrophic than in the tributary because of the treated sewage discharge, particularly in winter. These results indicated that feeding intensity differed between sites, particularly in winter, and this difference might be associated with differences in prey availability (i.e., chironomid larvae) or warm-water conditions. Moreover, juveniles could shift their use of food resources, in response to differences in prey availability. Thus, to conserve E. oxycephala in terms of early food resource use, it is necessary to conserve various aquatic prey animals such as atyid shrimps and chironomid larvae and their habitats.

Comparative Research on River Basin Management in the Sagami River Basin (Japan) and the Muda River Basin (Malaysia)

In the world, river basins often interwoven into two or more states or prefectures and because of that, disputes over water are common. Nevertheless, not all shared river basins are associated with water conflicts. Rivers in Japan and Malaysia play a significant role in regional economic development. They also play a significant role as water sources for industrial, domestic, agricultural, aquaculture, hydroelectric power generation, and the environment. The research aim is to determine the similarities and differences between the Sagami and Muda River Basins in order to have a better understanding of the governance needed for effectively implementing the lessons drawn from the Sagami River Basin for improving the management of the Muda River Basin in Malaysia. This research adopts qualitative and quantitative approaches. Semi-structured interviews were held with the key stakeholders from both basins and show that Japan has endeavored to present policy efforts to accommodate the innovative approaches in the management of their water resources, including the establishment of a river basin council. In Malaysia, there is little or no stakeholder involvement in the Muda River Basin, and the water resource management is not holistic and is not integrated as it should be. Besides that, there is little or no Integrated Resources Water Management, a pre-requisite for sustainable water resources. The results from this comparative study concluded that full support and participation from public stakeholders (meaning the non-government and non-private sector stakeholders) is vital for achieving sustainable water use in the Muda River Basin. Integrated Water Resources Management (IWRM) approaches such as the introduction of payments for ecosystems services and the development of river basin organization in the Muda River Basin should take place in the spirit of political willingness.

Taste and odor problems caused by nuisance algae for water supply in Sagami River System

相模川水系を水源とする神奈川県営水道では，貯水池である相模湖（相模ダム）や津久井湖（城山ダム）で繁殖した藻類が，浄水処理や水質に悪影響を及ぼす「生物障害」が問題となっている．これらの生物障害のなかで最も深刻なのは，かび臭による異臭味障害である．近年このかび臭障害が，上流の水源湖沼だけでなく，相模川本川で発生する事例が観察されている．本報では，相模川水系における異臭味障害について概説し，さらに，相模川本川中流域における湖沼性障害生物の繁殖事例と河床着生・付着藻類の調査結果について報告する．

Importance of antecedent environmental conditions in modeling species distributions

Although species distributions can change in an unexpectedly short period of time, most species distribution models (SDMs) use only long‐term averaged environmental conditions to explain species distributions. We aimed to demonstrate the importance of incorporating antecedent environmental conditions into SDMs in comparison to long‐term averaged environmental conditions. We modeled the presence/absence of 18 fish species captured across 108 sampling events along a 50‐km length of the Sagami River in Japan throughout the 1990s (one to four times per site at 45 sites). We constructed and compared the two types of SDMs: 1) a conventional model that uses only long‐term averaged (10‐yr) environmental conditions; and 2) a proposed model that incorporates environmental conditions 2 yr prior to a sampling event (antecedent conditions) together with long‐term averages linked to life‐history stages. These models both included geomorphological, hydrological, and sampling conditions as predictors. A random forest algorithm was applied for modeling and quantifying the relative importance of the predictors. For seven species, antecedent hydrological conditions were more important than the long‐term averaged hydrological conditions. Furthermore, the distributions of two species with low prevalence could not be predicted using long‐term averaged hydrological conditions but only using antecedent hydrological conditions. In conclusion, incorporating antecedent environmental factors linked with life‐history stages at appropriate time scales can better explain changes in species distribution through time.

Correlations between aromaticity of dissolved organic matter and trace metal concentrations in natural and effluent waters: A case study in the Sagami River Basin, Japan

Chemical speciation, reactivity, and bioavailability of trace metals in aqueous systems arestrongly influenced by dissolved organic matter (DOM). DOM is a mixture of diverse components, so a range of organic molecules potentially participates in the occurrence of dissolved trace metals. In this study, we investigated water quality variables that influence dissolved trace metal concentrations in natural and effluent water systems with a particular attention given to the relationship between DOM optical properties and dissolved copper and iron concentrations. We found that specific UV absorbance (SUVA254: an indicator of DOM aromaticity) has a significant correlation with dissolved trace metal to dissolved organic carbon concentration ratios ([Me]T/[DOC]) for copper and iron in natural freshwaters and treated municipal wastewater in the Sagami River basin, Japan. This trend was also prevalent for other freshwaters in temperate climates except for Fe-rich waters. Our findings indicate that the concentrations of dissolved copper and iron in natural and effluent waters are significantly influenced not only by DOM concentration, but also by aromaticity of DOM, and that this DOM property can be inferred from spectrophotometric measurements.

Effect of dissolved organic matter on Fe(II) oxidation in natural and engineered waters

Fe(II) oxidation was investigated in samples from the Sagami River basin (Japan) with particular emphasis on the effect of dissolved organic matter (DOM) in an urban river system. Collected samples consisted of main stream and tributary waters impacted to a moderate and minor extent by anthropogenic activities, respectively, and treated effluents from adjacent municipal wastewater treatment plants (MWWTPs: as representative anthropogenic point source). Nanomolar Fe(II) oxidation was measured in air-saturated waters using luminol chemiluminescence in the dark at 25 °C. Second-order rate constant for Fe(II) oxidation (with respect to Fe(II) and O2 concentrations) showed spatial and temporal variation. Annual average of the rate constant was highest for MWWTP effluents, followed by reservoir and river waters, with tributary waters showing the lowest oxidation rate. Manipulation experiments indicated that, in addition to pH (7.8–8.4), DOM characteristics are important explanatory variable for the Fe(II) oxidation. For example, the addition of MWWTP-derived humic-type DOM to anthropogenically less-influenced tributary water resulted in substantial increase in the oxidation rate. Significant negative correlation observed between the specific UV absorbance (SUVA254) and Fe(II) oxidation rate constant (pH 8.0) suggests a potential effect of humic-type DOM with low SUVA254 (high aliphatic content) on Fe(II) oxidation in natural and engineered waters.

神奈川県相模川流域における河川水及び水道水のネオニコチノイド系農薬等の実態調査

神奈川県相模川流域における河川水及び水道水のネオニコチノイド系農薬等の実態調査

Evaluation of Spatial Pattern of Altered Flow Regimes on a River Network Using a Distributed Hydrological Model.

Alteration of the spatial variability of natural flow regimes has been less studied than that of the temporal variability, despite its ecological importance for river ecosystems. Here, we aimed to quantify the spatial patterns of flow regime alterations along a river network in the Sagami River, Japan, by estimating river discharge under natural and altered flow conditions. We used a distributed hydrological model, which simulates hydrological processes spatiotemporally, to estimate 20-year daily river discharge along the river network. Then, 33 hydrologic indices (i.e., Indicators of Hydrologic Alteration) were calculated from the simulated discharge to estimate the spatial patterns of their alterations. Some hydrologic indices were relatively well estimated such as the magnitude and timing of maximum flows, monthly median flows, and the frequency of low and high flow pulses. The accuracy was evaluated with correlation analysis (r > 0.4) and the Kolmogorov–Smirnov test (α = 0.05) by comparing these indices calculated from both observed and simulated discharge. The spatial patterns of the flow regime alterations varied depending on the hydrologic indices. For example, both the median flow in August and the frequency of high flow pulses were reduced by the maximum of approximately 70%, but these strongest alterations were detected at different locations (i.e., on the mainstream and the tributary, respectively). These results are likely caused by different operational purposes of multiple water control facilities. The results imply that the evaluation only at discharge gauges is insufficient to capture the alteration of the flow regime. Our findings clearly emphasize the importance of evaluating the spatial pattern of flow regime alteration on a river network where its discharge is affected by multiple water control facilities.

A study on the existence of Vibrio cholerae non-O1 in the river.

The aim of the present study is Vibrio cholerae non-O1 existing in river. Bacteria are known to inhabit all kinds of environment. Vibrionaceae is widely distributed in environmental water. Vibrio spp. have been identified as a cause of toxicity in fish and shellfish. One condition affecting the survival of pathogenic microorganisms in environmental water is the salt concentration, and they have been reported to inhabit brackish water. However, V. cholerae non-O1 has also been detected in fresh water, and its properties suggest that it can survive in river water. Sampling was performed 4 times at 4 points during a 5-month period from July to November at about 1-month intervals from the Sagami River in 1985. River water bacteria were identified, and V. cholera non-O1 isolated. I investigated the relationship between the bacterial flora in river water and the detection of V. cholerae non-O1. There were significant differences in the composition of bacterial flora with and without the isolation of V. cholerae non-O1 (Chi-square test) (χ(2) = 24.70 > 22.0 (p = 0.005), df = 8). A correlation between changes in the composition of the river water bacterial flora and detection of V. cholerae non-O1 was identified. Therefore, V. cholerae non-O1 exists in the river.

Modelling basin-scale distribution of fish occurrence probability for assessment of flow and habitat conditions in rivers

Flow regimes play an important role in sustaining biodiversity in river ecosystems. However, the effects of flow regimes on riverine fish have not been clearly described. Therefore, we propose a new methodology to quantitatively link habitat conditions (such as flow indices and physical habitat conditions) to the occurrence probability (OP) of fish species. We developed a basin-scale fish distribution model by integrating the concept of habitat suitability assessment with a distributed hydrological model in order to estimate the OP of fish, with particular attention to flow regime. A generalized linear model was used to evaluate the relationship between the probabilities of fish occurrence and major environmental factors in river sections. A geomorphology-based hydrological model was adopted to simulate river discharge, which was used to calculate 10 flow indices. The occurrence probabilities of 50 fish species in the Sagami River in Japan were modelled. For the prediction accuracy, field survey results that included at least five observations of both the presence and the absence of each species were required to obtain relatively reliable prediction (accuracy > 60%). Using the developed model, important habitat conditions for each species were identified, which showed the importance of low-flow events for more than 10 species, including Hypomesus nipponensis and Rhinogobius fluviatilis. The model also confirmed the positive effects of natural flow and the negative effect of river-crossing structures, such as dams and weirs, on the OP of most species. The suggested approach enables us to evaluate and project the ecological consequences of water resource management policy. The results demonstrate the applicability of the fish distribution model to provide quantitative information on the flow required to maintain fish communities.Editor Z.W. Kundzewicz; Guest editor M. AcremanCitation Sui, P., Iwasaki, A., Saavedra, V.O.C., and Yoshimura, C., 2013. Modelling basin-scale distribution of fish occurrence probability for assessment of flow and habitat conditions in rivers. Hydrological Sciences Journal, 59 (3–4), 618–628.

Late arrival of Anguilla japonica glass eels at the Sagami River estuary in two recent consecutive year classes: ecology and socio-economic impacts

To determine the actual status of the recruiting glass eel stock of Anguilla japonica, we conducted a continuous monthly monitoring program for 2 years between November 2009 and October 2011 at the Sagami River estuary, Japan. A total of 114 and 372 A. japonica glass eels were observed in the 2009–2010 and 2010–2011 seasons, respectively. Recruitment patterns were the same in both years, starting in early winter (December in 2009 and November in 2010), increasing slightly until March, decreasing in April, but attaining the largest peak in June, after which no glass eels were observed during August–October. The Japanese eel has been known to spawn mainly in the summer, and glass eels recruit to their freshwater growth habitats during the winter to early spring. Our results clearly demonstrate an unexpected late arrival of glass eels in the early summer for two recent consecutive year classes. The summer recruitment found in our study indicates the unusual phenology of the Japanese eel, which may be a possible response to recent climate change.

Distribution coefficients (K d) of stable iodine in estuarine and coastal regions, Japan, and their relationship to salinity and organic carbon in sediments

The sediment-water distribution coefficient, (K(d)), is one of the most important parameters in radionuclide assessment models. In this study, we determined K ds of stable iodine (I) in estuarine and coastal regions. We studied 16 estuarine and coastal regions of Japan and obtained I data on water and sediments. Data on salinity, pH, dissolved organic carbon and dissolved oxygen in water, and organic carbon (OC) in sediments were also obtained as estuarine variables. Determined (K(d))S of I in the Sagami River estuary decreased along the salinity gradient (salinity range, 0.1-33.8), indicating that salinity is one of the important factors controlling the (K(d)) values; however, when the (K(d)) values were compared among all the estuaries, the difference between minimum and maximum (K(d)) values varied by about two orders of magnitude in a narrow salinity range of 30.0-34.4. A significant correlation between (K(d)) value and OC content in sediments was observed in all the stations with a salinity of ≥ 30 except for stations in the Ishikari and Onga River estuaries. The exceptions are probably due to different sources of the sediments, which are explained by the results of relatively low I/OC ratios in sediments in those two estuaries, compared to the other estuaries. Thus, OC in sediments as well as salinity may be responsible for the variation of (K(d))S of I in the estuarine and coastal regions.

Distributions of trace metals Co, Cu and Cd in northern Sagami Bay, Japan and their relationship to estuarine variables

Concentrations of the trace metals Co, Cu and Cd in dissolved (<0.2μm) and particulate (>0.2μm) phases in surface waters were determined to test whether DOC, which is an indicator of dissolved organic matter (DOM), and organic matter (OM) in suspended particulate matter (SPM) act as important estuarine variables controlling the distributions of these metals in the estuarine zone. Although the dissolved metals in the surface waters from the Sagami River to northern Sagami Bay had different behaviors in June, August, and November, 2008, concentrations of dissolved Co and Cu linearly correlated with DOC concentration, but with different slopes for fresh (salinity of ≤0.1) and estuarine (salinity of >0.1) waters. This difference in the water regime between those two metals and the DOC in Sagami Bay indicates that there are differences in composition between riverine and estuarine DOM, due to change of the composition by biogeochemical processes and the presence of additional sources, or that seawater cations are competing for binding sites of DOM during the estuarine mixing. As for particulate phase, there was no relationship between the concentrations of particulate metals and that of OM in SPM at low river flows (i.e., June and November surveys). It is thought that change of the OM composition by the additional SPM sources (anthropogenic discharge and resuspension from the seabed) contributes to the affinity of trace metals for sorption sites on the surfaces of the SPM, thereby making the evaluation of importance of OM in SPM difficult. On the other hand, at high river flow (August survey), riverine SPM significantly contributed to the estuarine SPM and it entered northern Sagami Bay with negligible composition change; however, there were weak correlation coefficients of particulate Co and Cd to OM in SPM, and there was no linear relationship between particulate Cu and OM in SPM. This can be attributed to the imbalanced competition between particle sorption and organic/inorganic complexation for Co and Cd, and prevention of particle sorption by binding Cu more strongly to dissolved organic ligands.

河口デルタ復元に要する期待流出土砂量-神奈川県相模川の例-

The Sagami River flowing into Sagami Bay is the main source of sand to the Shonan coast of 16 km length extending between Oiso Port and Enoshima Island. In the upper stream of this river, large dams were constructed and large-scale river bed excavation had been carried out to obtain construction materials before 1967. These resulted in the decrease in sediment supply from 1.5x105 m3/yr to 5000 m3/yr and the shoreline recession around the river mouth. In this study, an expected fluvial sand supply for reforming a river mouth delta of the Sagami River was investigated, using the contour-line-change model considering grain size changes. It was concluded that the expected sand supply from the river necessary for recovering the river delta within 30 years from the present was (1.0-1.5)x105 m3/yr.

Bacterial community structure analysis of sediment in the Sagami River, Japan using a rapid approach based on two-dimensional DNA gel electrophoresis mapping with selective primer pairs

A rapid approach based on two-dimensional DNA gel electrophroesis (2-DGE) mapping with selective primer pairs was employed to analyze bacterial community structure in sediments from upstream, midstream and downstream of Sagami River in Japan. The 2-DGE maps indicated that Alpha- and Delta-proteobacteria were major bacterial populations in the upstream and midstream sediments. Further bacterial community structure analysis showed that richness proportion of Alpha- and Delta-proteobacterial groups reflected a trend toward decreasing from the upstream to downstream sediments. The biomass proportion of bacterial populations in the midstream sediment showed a significantly difference from that in the other sediments, suggesting that there may be an environmental pressure on the midstream bacterial community. Lorenz curves, together with Gini coefficients were successfully applied to the 2-DGE mapping data for resolving evenness of bacterial populations, and showed that the plotted curve from high-resolution 2-DGE mapping became less linear and more an exponential function than that of the 1-DGE methods such as chain length analysis and denaturing gradient gel electrophoresis, suggesting that the 2-DGE mapping may achieve a more detailed evaluation of bacterial community. In conclusion, the 2-DGE mapping combined with the selective primer pairs enables bacterial community structure analysis in river sediment and thus it can also monitor sediment pollution based on the change of bacterial community structure.