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1.
Cadmium and other heavy metals lead to environmental danger, and these heavy metals are a great threat to human and other animal’s health. Investigation of the relationship between survival of E. coli and metallothionein smtA gene expression against cadmium ion is the goal of this research. Survival of recombinant bacteria containing smtA gene was analyzed against various concentrations of cadmium chloride salt using optical density (OD). At the resistive range, recombinant bacteria were subjected to different treatments. At the logarithmic phase of bacterial growth, sampling, RNA extraction and cDNA synthesis were performed and smtA gene expression was then analyzed by real-time PCR using designed primers for smtA gene and Amp resistance (as the calibrator gene). Relative gene expression was calculated using the ??Ct method. The resistive range against cadmium chloride was 0.5–0.7 mM (minimum inhibitory concentration (MIC = 0.5 mM)). Survival and gene expression analysis showed that in induced bacteria, smtA expression was increased significantly that in turn conferred resistance to cadmium chloride prominently. There was a direct relationship between increased smtA gene expression and survival of the recombinant bacteria. Therefore, our result may help to confront to cadmium metal environmental pollution using overexpression of smtA gene expression in recombinant bacteria.  相似文献   

2.
There is currently limited research available on the secondary metabolites of moulds in workplaces. The aim of this study was to determine the mould contamination in museums (N = 4), composting plants (N = 4) and tanneries (N = 4) and the secondary metabolite profiles of Alternaria, Aspergillus and Penicillium isolates from these workplaces. Alternaria, Aspergillus and Penicillium species were identified using the ITS1/2 sequence of the rDNA region. Mould metabolites were quantitatively analysed on standard laboratory medium and mineral medium containing materials specific to each workplace using liquid chromatography-mass spectrometry. We also examined the cytotoxicity of the moulds using MTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide) assays. Air microbiological contamination analyses showed a number of microorganisms, ranging from 2.4 × 103 CFU m?3 (composting plants) to 6.8 × 104 CFU m?3 (tanneries). We identified high percentages of Alternaria, Aspergillus and Penicillium moulds (air 57–59%, surfaces 10–65%) in all workplaces. The following moulds were the most cytotoxic (>90%): Alternaria alternata, A. limoniasperae, Aspergillus flavus, Penicillium biourgeianum, P. commune and P. spinulosum. The same mould species isolated from different working environments exhibited varying toxigenic and cytotoxic properties. Modifying the culture medium to simulate environmental conditions most often resulted in the inhibition of secondary metabolite production. Moulds isolated from the working environments produced the following mycotoxins (ng g?1): chanoclavines (0.28–204), cyclopiazonic acid (27.1–1045), fumigaclavines (0.33–10,640,000), meleagrin (0.57–13,393), roquefortins (0.01–16,660), rugulovasines (112–220), viridicatin (0.12–957), viridicatol (4.23–2753) and quinocitrinines (0.07–1104), which may have a negative impact on human health.  相似文献   

3.
Binary mixture of Variovorax sp. BS1 and Achromobacter denitrificans degraded >99 % of 300 mg l?1 of ortho-dimethyl phthalate (DMP) within 24 h of incubation at 30 °C. Rate of degradation of DMP followed the order: A. denitrificans > binary mixture > Variovorax sp. BS1. Transient intermediate metabolites were not detected using HPLC analyses at any time points using Variovorax sp. BS1 and binary mixture. However, using pure culture of A. denitrificans, monomethyl phthalate was accumulated during the course of DMP biodegradation which disappeared with time of incubation. Binary mixture of Variovorax sp. BS1 and A. denitrificans exhibited better efficiency in terms of biodegradation of DMP as compared to either individual bacterial strain. In addition, fluorescence in situ hybridization technique was used to estimate the population dynamics of Variovorax sp. BS1 in binary mixture. A. denitrificans in mixed culture were estimated by subtracting total number of cells of Variovorax sp. BS1 from the total counts of microbial cells using an epifluorescence microscope after staining with 4′,6-diamidino-2-phenylindole. Results obtained at mid-exponential growth phase suggested the abundance of both bacterial strains as primary degraders.  相似文献   

4.
The feeding behavior of three species of mussels, the native Ischadium recurvum and the invasives Mytella charruana and Perna viridis, was studied in an invaded ecosystem in Florida (USA). In situ feeding experiments using the biodeposition method were performed along a salinity gradient in four different locations along the St. Johns River. Water characteristics, such as salinity, temperature, dissolved oxygen, and seston loads, were recorded to identify relationships between these variables and the feeding behavior of the mussels. Feeding behavior of the species varied by study site. Clearance, filtration, organic ingestion, and absorption rates of I. recurvum were negatively affected by salinity. For the invasive mussel, M. charruana, rejection was positively related to salinity while total ingestion, organic ingestion, and absorption rates were positively related to the percentage of organic matter in the seston. For P. viridis, total and organic ingestion rates were negatively affected by salinity but positively affected by total particulate matter. Condition indices for P. viridis and M. charruana were 13.16?±?0.64 and 6.63?±?0.43, respectively, compared to 4.82?±?0.41 for the native species I. recurvum, indicating that these mussels are well adapted to the environmental conditions in the area. This study indicates that the three species have different preferred habitats because of their specific responses to water characteristics. Thus, the invasive mussels will not totally occupy the niche of the native mussel in Florida despite overlapping zones. These data may help identify potential invaded areas and understand the extent of the invasion.  相似文献   

5.
Coastal ecosystems are exposed to changes in physical-chemical properties, such as those occurring in upwelling and freshwater-influenced areas. In these areas, inorganic carbon can influence seawater properties that may affect organisms and populations inhabiting benthic habitats such as the intertidal mussel Perumytilus purpuratus. Feeding and metabolic responses were measured in adult mussels from two geographic regions (central and southern Chile) and two local habitats (river-influenced and non-river-influenced) and three pCO2 levels (380, 750, and 1200 μatm pCO2 in seawater). The feeding rates of mussels tend to increase at high pCO2 levels in seawater; however this response was variable across regions and local habitats. In contrast, there was no difference in the respiratory rate of mussels between geographic areas, but there was a significant reduction of oxygen consumption at intermediate and high levels of pCO2. The results indicate that river-influenced organisms compensate for reductions in metabolic cost at elevated pCO2 levels by having their energy demands met, in contrast with non-river-influenced organisms. The lack of regional-scale variability in the physiological performance of mussels may indicate physiological homogeneity across populations and thus potential for local adaptation. However, the local-scale influences of river- and non-river-influenced habitats may counterbalance this regional response promoting intra-population variability and phenotypic plasticity in P. purpuratus. The plasticity may be an important mechanism that allows mussels to confront the challenges of projected ocean acidification scenarios.  相似文献   

6.
To evaluate the impact of invading seagrass on biogeochemical processes associated with sulfur cycles, we investigated the geochemical properties and sulfate reduction rates (SRRs) in sediments inhabited by invasive warm affinity Halophila nipponica and indigenous cold affinity Zostera marina. A more positive relationship between SRR and below-ground biomass (BGB) was observed at the H. nipponica bed (SRR = 0.6809 × BGB ? 4.3162, r 2 = 0.9878, p = 0.0006) than at the Z. marina bed (SRR = 0.3470 × BGB ? 4.0341, r 2 = 0.7082, p = 0.0357). These results suggested that SR was more stimulated by the dissolved organic carbon (DOC) exuded from the roots of H. nipponica than by the DOC released from the roots of Z. marina. Despite the enhanced SR in spring-summer, the relatively lower proportion (average, 20%) of acid-volatile sulfur (AVS) in total reduced sulfur and the strong correlation between total oxalate-extractable Fe (Fe(oxal)) and chromium-reducible sulfur (CRS = 0.2321 × total Fe(oxal) + 1.8180, r 2 = 0.3344, p = 0.0076) in the sediments suggested the rapid re-oxidation of sulfide and precipitation of sulfide with Fe. The turnover rate of the AVS at the H. nipponica bed (0.13 day?1) was 2.5 times lower than that at the Z. marina bed (0.33 day?1). Together with lower AVS turnover, the stronger correlation of SRR to BGB in the H. nipponica bed suggests that the extension of H. nipponica resulting from the warming of seawater might provoke more sulfide accumulation in coastal sediments.  相似文献   

7.
Seagrass populations have been declining globally, with changes attributed to anthropogenic stresses and, more recently, negative effects of global climate change. We examined the distribution of Zostera marina (eelgrass) dominated beds in the York River, Chesapeake Bay, VA over an 8-year time period. Using a temperature-dependent light model, declines in upriver areas were associated with higher light attenuation, resulting in lower light availability relative to compensating light requirements of Z. marina compared with downriver areas. An inverse relationship was observed between SAV growth and temperature with a change between net bed cover increases and decreases for the period of 2004–2011 observed at approximately 23 °C. Z. marina-dominated beds in the lower river have been recovering from a die-off event in 2005 and experienced another near complete decline in 2010, losing an average of 97 % of coverage of Z. marina from June to October. These 2010 declines were attributed to an early summer heat event in which daily mean water temperatures increased from 25 to 30 °C over a 2-week time period, considerably higher than previous years when complete die-offs were not observed. Z. marina recovery from this event was minimal, while Ruppia maritima (widgeongrass) expanded its abundance. Water temperatures are projected to continue to increase in the Chesapeake Bay and elsewhere. These results suggest that short-term exposures to rapidly increasing temperatures by 4–5 °C above normal during summer months can result in widespread diebacks that may lead to Z. marina extirpation from historically vegetated areas, with the potential replacement by other species.  相似文献   

8.
The crystal chemistry and the elastic behavior under isothermal conditions up to 9 GPa of a natural, and extremely rare, 3T-phlogopite from Traversella (Valchiusella, Turin, Western Alps) [(K0.99Na0.05Ba0.01)(Mg2.60Al0.20Fe 0.21 2+ )[Si2.71Al1.29O10](OH)2, space group P3112, with a = 5.3167(4), c = 30.440(2) Å, and V = 745.16(9) ų] have been investigated by electron microprobe analysis in wavelength dispersion mode, single-crystal X-ray diffraction at 100 K, and in situ high-pressure synchrotron radiation powder diffraction (at room temperature) with a diamond anvil cell. The single-crystal refinement confirms the general structure features expected for trioctahedral micas, with the inter-layer site partially occupied by potassium and sodium, iron almost homogeneously distributed over the three independent octahedral sites, and the average bond distances of the two unique tetrahedra suggesting a disordered Si/Al-distribution (i.e., 〈T1-O〉 ~ 1.658 and 〈T2-O〉 ~ 1.656 Å). The location of the H-site confirms the orientation of the O–H vector nearly perpendicular to (0001). The refinement converged with R 1(F) = 0.0382, 846 unique reflections with F O > 4σ(F O) and 61 refined parameters, and not significant residuals in the final difference-Fourier map of the electron density (+0.77/?0.37 e ?/Å3). The high-pressure experiments showed no phase transition within the pressure range investigated. The P–V data were fitted with a Murnaghan (M-EoS) and a third-order Birch-Murnaghan equation of state (BM-EoS), yielding: (1) M-EoS, V 0 = 747.0(3) Å3, K T0 = 44.5(24) GPa, and K′ = 8.0(9); (2) BM-EoS, V 0 = 747.0(3) Å3, K T0 = 42.8(29) GPa, and K′ = 9.9(17). A comparison between the elastic behavior in response to pressure observed in 1M- and 3T-phlogopite is made.  相似文献   

9.
Axenic culture of microalgae Chlorella vulgaris ATCC® 13482 and Scenedesmus obliquus FACHB 417 was used for phycoremediation of primary municipal wastewater. The main aim of this study was to measure the effects of normal air and CO2-augmented air on the removal efficacy of nutrients (ammonia N and phosphate P) from municipal wastewater by the two microalgae. Batch experiments were carried out in cylindrical glass bottles of 1 L working volume at 25 °C and cool fluorescent light of 6500 lux maintaining 14/10 h of light/dark cycle with normal air supplied at 0.2 L min?1 per liter of the liquid for both algal strains for the experimental period. In the next set of experiments, the treatment process was enhanced by using 1, 2 and 5% CO2/air (vol./vol.) supply into microalgal cultures. The enrichment of inlet air with CO2 was found to be beneficial. The maximum removal of 76.3 and 76% COD, 94.2 and 92.6% ammonia, and 94.8 and 93.1% phosphate after a period of 10 days was reported for C. vulgaris and S. obliquus, respectively, with 5% CO2/air supply. Comparing the two microalgae, maximum removal rates of ammonia and phosphate by C. vulgaris were 4.12 and 1.75 mg L?1 day?1, respectively, at 5% CO2/air supply. From kinetic study data, it was found that the specific rates of phosphate utilization (q phsophate) by C. vulgaris and S. obliquus at 5% CO2/air supply were 1.98 and 2.11 day?1, respectively. Scale-up estimation of a reactor removing phosphate (the criteria pollutant) from 50 MLD wastewater influent was also done.  相似文献   

10.
Here, a novel one-dimensional composite of poly(m-phenylenediamine)s coating on filamentous Streptomyces was successfully constructed via a controllable polymerization reaction. The synthesized composites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Their adsorption isotherm and kinetics for aqueous hexavalent chromium were also systematically examined. The results of scanning electron microscopy analysis indicated that the obtained composites based on Streptomyces were showed a uniform and stable one-dimensional morphology with distinct core–shell configuration. Moreover, the Langmuir isotherm model (R 2 > 0.96) and pseudo-second-order equation (R 2 = 0.9996) described well the equilibrium adsorption behavior and kinetics of hexavalent chromium adsorption by the composites. In addition, bath adsorption experiments demonstrated the highest adsorption capacity of hexavalent chromium by the composites reached 320.03 mg g?1 in an acid solution, which was 5.6 times as that of the pure Streptomyces filaments. The results of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses suggested that the adsorption of hexavalent chromium by the composites possibly involved the protonation, redox, and chelation reactions. Therefore, a promising application of these composites in treating acid hexavalent chromium-contaminated wastewater is expectable.  相似文献   

11.
Contamination of soil with heavy metals is one of the important concerns of public health and food production. Nickel is a heavy metal whose toxic properties have been confirmed. In some plants, nickel has also been known as a useful metal for their growth. In this research, the response of two chamomile species to different levels of nickel was investigated in two stages of germination and callogenesis in vitro conditions in factorial experiment based on completely randomized design. In the first experiment, the effect of different concentrations of nickel sulfate (0, 60, 120, and 180 µM) was examined on germination of German (Matricaria chamomilla) and Aurea (M. aurea) chamomile seeds in the MS culture medium. The results indicated that at high levels of nickel sulfate, the speed and percentage of germination increased in both types of chamomile. In M. chamomilla, with the increase in the concentration of nickel sulfate, the length of the seedling decreased, but the seed weight vigor, length of the radicle, and dry weight of the seedling increased. M. aurea showed elevation in most indices. The results of the second experiment indicated that the M. chamomilla leaf explants had callogenesis and its callogenesis indices showed a significant decrease at high levels of nickel, when compared with the control In M. aurea, the calluses did not grow sufficiently, suggesting the sensitivity of M. aurea’s callogenesis to the presence of different levels of nickel. In conclusion, chamomile appears to be tolerant to nickel stress.  相似文献   

12.
Pile foundations are often subject to lateral loading due to various forces on a variety of structures like high rise buildings, transmission towers, power stations, offshore structures and highway and railway structures. The present investigation is to study the effect of slopes on p-y curves (where p is the static soil reaction and y is the pile deflection) due to static lateral loading in soft clay (Consistency index Ic = 0.42). A series of laboratory model tests were carried out on the instrumented model pile on sloping ground (slopes of 1V:1H, 1V:1.5H, 1V:2H, 1V:3H and 1V:5H) and with varying embedment length to diameter ratio (L/D) of 20, 25 and 30. From the experimental results, the bending moment curves along the pile shaft are double differentiated to obtain the soil resistance (p) and double integrated to obtain the deflection (y) using curve fitting method. New p-y curves for piles located on crest of soft clay with different sloping ground surface under static lateral loading are developed. Moreover, the effect of sloping angles on proposed p-y curves was studied.  相似文献   

13.
This study is focused on the use of ultrasound to disrupt Microcystis aeruginosa growth, with consideration for the gap between laboratory-scale experiment and field application. Laboratory-scale sonication systems with different frequencies (i.e., 20, 584, 869, and 1137 kHz) for 30 min at 10-min intervals were conducted to investigate their effectiveness at disrupting M. aeruginosa growth. The toxicological effect of sonicated M. aeruginosa including microcystin-LR was also evaluated using a Daphnia magna acute toxicity test. High frequencies, 869 and 1137 kHz, resulted in more than a 60% reduction of cells after 30 min of sonication. Low to middle frequencies, 20 and 584 kHz, only showed a 30% reduction of cells after 30 min of sonication. High frequencies also led to the inactivation of cell proliferation during M. aeruginosa regrowth, due to cellular destruction and finally cell death. However, the concentration of microcystin-LR and the potential adverse effects of M. aeruginosa on D. magna could not be controlled using ultrasonic frequencies. Therefore, our results suggest that ultrasonic frequencies between 869 and 1137 kHz are effective at controlling bloom formation in M. aeruginosa and the regrowth of M. aeruginosa after sonication, but not at controlling microcystin-LR concentrations and its adverse effects on D. magna. Consequently, a combined purification technology to reduce the cyanotoxins such as microcystin-LR, rather than ultrasonic frequency alone, will be needed to control M. aeruginosa growth and its toxicity levels in the aquatic environment.  相似文献   

14.
Alteration of estuarine shorelines associated with increased urbanization can significantly impact biota and food webs. This study determined the impact of shoreline alteration on growth and movement of the estuarine fish Fundulus heteroclitus in a tributary of the Delaware Coastal Bays. Fundulus heteroclitus is abundant along the east coast of the USA, and is an important trophic link between marsh and subtidal estuary. The restricted home range of F. heteroclitus allowed discrete sampling, and fish growth comparisons, along 35–65-m long stretches of fringing Spartina alterniflora and Phragmites australis marsh, riprap, and bulkhead. Fundulus heteroclitus were tagged with decimal Coded Wire Tags. Of 725 tagged F. heteroclitus, 89 were recaptured 30–63 days later. Mean growth rate (0.06–0.15 mm day?1 across all shoreline types) was greatest at riprap, lowest at Spartina and Phragmites, and intermediate at bulkhead, where growth was not significantly different from any other shoreline. This suggests that discernible environments exist along different shoreline types, even at the scale of tens of meters. No difference in movement distance was detected at different shoreline types; most individuals displayed a high degree of site fidelity. Forty-seven percent were recaptured within 5 m of their tagging location, although alongshore movements up to 475 m were recorded. Estimates of relative F. heteroclitus productivity, using relative density data from a concurrent study, were highest along Spartina and Phragmites, intermediate at riprap, and lowest at bulkhead. Therefore, despite greater growth rates along riprap than at vegetated shores, armoring reduces abundance sufficiently to negatively impact localized productivity of F. heteroclitus.  相似文献   

15.
Effects of initial concentrations of Moringa oleifera seed coagulant for removing Chemical Oxygen Demand and Total Dissolved Solids from municipal solid waste leachate have been evaluated at an optimum pH of 7 and temperature of 318 K. The kinetic data obtained from the experiments were fitted to the pseudo first-order, pseudo second-order, Elovich and intraparticle diffusion models. Based on a regression coefficient (R 2), the equilibrium (kinetic) data were best fitted with the Elovich model (R 2 = 0.993 for Chemical Oxygen Demand and R 2 = 0.996 for Total Dissolved Solids) than that of other models. The results of the kinetic models study indicated that the adsorption capacity of M. oleifera seed as a coagulant for removing Chemical Oxygen Demand and Total Dissolved Solids in a leachate increased up to 100 mg L?1, beyond which the adsorption capacity got reduced. Finally, the present study concluded that M. oleifera seed coagulant could be employed effectively for the removal of Chemical Oxygen Demand and Total Dissolved Solids in a municipal solid waste leachate.  相似文献   

16.
Abundance of the prymnesiophyte Phaeocystis pouchetii was quantified via light microscopy at 2-week to monthly intervals in Massachusetts Bay (southern Gulf of Maine, NW Atlantic) during 1992–2012. Variability in the abundance and seasonal cycle of Phaeocystis are described and synoptic hydrographic, nutrient, and meteorological data were analyzed to identify factors that may influence Phaeocystis abundance. The maximum Phaeocystis abundance was 14?×?106 cells L?1 (10 Apr 2008). It was frequently (5 of 8 years) absent prior to year 2000, but not thereafter. Seasonally, it first appeared in February to early March, reached peak abundance in mid-April, and persisted until May or early June for a duration of 0–112 days (mean 34 days). A long-term alternation between Phaeocystis and centric diatom abundance was apparent, suggesting winter-spring selection of either Phaeocystis or centric diatoms. Phytoplankton community analysis suggested that blooms affected the rest of the phytoplankton community. Phaeocystis blooms were manifest as a substantial increase in particulate nutrients above normal levels. Phaeocystis blooms were preceded in February by a slightly elevated concentration of NO3 (9.3 vs. 6.5 μM when absent) and PO4 (0.99 vs. 0.79 μM when absent). Blooms were also preceded by elevated ratios of NO3/PO4, NO3/Si, and PO4/Si, and warmer, saltier waters reflecting reduced river discharge. The correlation with salinity and river discharge suggests that Phaeocystis bloom variability is partially determined by annually varying circulation processes that determine the degree of low nutrient, low salinity coastal water intrusion into Massachusetts Bay.  相似文献   

17.
While multiple species of macroalgae and seagrass can benefit from elevated CO2 concentrations, competition between such organisms may influence their ultimate responses. This study reports on experiments performed with a Northwest Atlantic species of the macroalgae, Ulva, and the seagrass, Zostera marina, grown under ambient and elevated levels of pCO2, and subjected to competition with each other. When grown individually, elevated pCO2 significantly increased growth rates and productivity of Ulva and Zostera, respectively, beyond control treatments (by threefold and 27%, respectively). For both primary producers, significant declines in tissue δ13C signatures suggested that increased growth and productivity were associated with a shift from use of HCO3? toward CO2 use. When grown under higher pCO2, Zostera experienced significant increases in leaf and rhizome carbon content as well as significant increases in leaf carbon-to-nitrogen ratios, while sediments within which high CO2 Zostera were grown had a significantly higher organic carbon content. When grown in the presence of Ulva; however, above- and below-ground productivity and tissue nitrogen content of Zostera were significantly lower, revealing an antagonistic interaction between elevated CO2 and the presence of Ulva. The presence of Zostera had no significant effect on the growth of Ulva. Collectively, this study demonstrates that while Ulva and Zostera can each individually benefit from elevated pCO2 levels, the ability of Ulva to grow more rapidly and inhibit seagrass productivity under elevated pCO2, coupled with accumulation of organic C in sediments, may offset the potential benefits for Zostera within high CO2 environments.  相似文献   

18.
The revised representatives of ammonite genera Malbosiceras and Pomeliceras from the Berriasian of the Crimean Mountains are classed with seven species, four of the first genus [M. malbosi (Pictet), M. chaperi (Pictet), M. broussei (Mazenot), M. pictetiforme Tavera] and three of the second one [P. aff. boisseti Nikolov, P. breveti (Pomel), P. (?) funduklense Lysenko et Arkadiev sp. nov.]. The identified species are described. The genus Mazenoticeras is considered as synonym of Malbosiceras. The above species prove that all the Berriasian zones (jacobi, occitanica and boissieri) are characteristic of corresponding deposits in the Crimean Mountains.  相似文献   

19.
The study of low-cost techniques for the tertiary treatment of wastewater is of global interest; above all low-energy techniques that do not require the use of chemicals. In this study, a wastewater treatment technology based on the filtration by a zooplanktonic population (Daphnia magna) is studied in controlled laboratory and mesocosm experiments for different hydraulic retention times (HRT). The efficiency of the treatment is evaluated in terms of particle removal efficiency. From laboratory experiments, HRT over 12 h and Daphnia concentrations above 50 individuals l?1 guarantee a particle removal efficiency greater than 30 %. However, low HRT of 6 h would require Daphnia concentrations above 70 individuals l?1 in order to obtain a particle removal efficiency of 20 %. The minimum removal efficiency of 2 % was for HRT = 3 h, independent of the Daphnia concentration. In the mesocosm, the growth of Daphnia individuals enhanced Daphnia magna filtering rates and higher removal efficiencies than those in the laboratory for the same HRT range. In the mesocosm experiments E. coli concentrations were reduced to a maximum of 2 logarithmic units. A balance equation model is proposed to predict particle removal efficiencies for varying HRT.  相似文献   

20.
A high-spatial resolution study design was used to investigate the relationship between land use practices, stream physicochemistry, hydroclimate, and stream Escherichia (E) coli concentrations in a mixed-land-use watershed in the Appalachian region. Stream samples were collected daily from six monitoring sites and analyzed for total E. coli counts using an enzyme metabolism indicator method. Statistical comparison of E. coli concentration time series showed significant (p?<?0.05) differences between study sites. Although highest average E. coli concentrations were observed at two agricultural sites (534 and 582 colony-forming counts (CFU) per 100 mL, respectively), highest total loadings were observed within the receiving stream, with values increasing downstream (2?×?1012 and 4.2?×?1012 study total CFU for bracketed upstream and downstream sites, respectively). No single physical variable displayed a significant correlation (p?<?0.05) with observed E. coli concentration at every site. However, sites displayed different patterns of significant correlations (p?<?0.05) between E. coli concentration and both physicochemical (e.g. pH, dissolved oxygen saturation) and hydroclimate variables (e.g. streamflow and precipitation). Percent agricultural land cover was the only land use category that showed significant (p?<?0.04) correlation with study average E. coli concentrations, thereby emphasizing the importance of land use practices to stream pathogen regimes. Results validate the analytical method and provide high-resolution, detailed, quantitative characterizations of stream E. coli regimes, thereby supplying land and water resource managers with science-based information to advance management decisions and improve public health.  相似文献   

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