The Experts below are selected from a list of 3300 Experts worldwide ranked by ideXlab platform
Dudley D Williams - One of the best experts on this subject based on the ideXlab platform.
-
bacterial community dynamics in the Hyporheic Zone of an intermittent stream
The ISME Journal, 2012Co-Authors: Roberta R. Fulthorpe, Catherine M Febria, Paul Beddoes, Dudley D WilliamsAbstract:The dynamics of in situ bacterial communities in the Hyporheic Zone of an intermittent stream were described in high spatiotemporal detail. We assessed community dynamics in stream sediments and interstitial pore water over a two-year period using terminal-restriction fragment length polymorphism. Here, we show that sediments remained saturated despite months of drought and limited hydrologic connectivity. The intermittency of stream surface water affected interstitial pore water communities more than Hyporheic sediment communities. Seasonal changes in bacterial community composition was significantly associated with water intermittency, phosphate concentrations, temperature, nitrate and dissolved organic carbon (DOC) concentrations. During periods of low- to no-surface water, communities changed from being rich in operational taxonomic units (OTUs) in isolated surface pools, to a few OTUs overall, including an overall decline in both common and rare taxa. Individual OTUs were compared between porewater and sediments. A total of 19% of identified OTUs existed in both porewater and sediment samples, suggesting that bacteria use Hyporheic sediments as a type of refuge from dessication, transported through hydrologically connected pore spaces. Stream intermittency impacted bacterial diversity on rapid timescales (that is, within days), below-ground and in the Hyporheic Zone. Owing to the coupling of intermittent streams to the surrounding watershed, we stress the importance of understanding connectivity at the pore scale, consequences for below-ground and above-ground biodiversity and nutrient processing, and across both short- and long-time periods (that is, days to months to years).
-
sources and seasonal patterns of dissolved organic matter dom in the Hyporheic Zone
Hydrobiologia, 2010Co-Authors: Jessica Wong, Dudley D WilliamsAbstract:The Hyporheic Zone is a region underneath streambeds that integrates surface and groundwater. Although its location is central to biogeochemical linkages between the riparian Zone, dissolved nutrients, and benthic biota, the seasonal quality and likely sources of dissolved organic matter (DOM) in the Hyporheic Zone are not well understood. To investigate DOM characteristics in the Hyporheic Zone, water from the surface and subsurface (at depths 20, 60, and 100 cm below the streambed) was sampled every 4 weeks from 2007 to 2008 in a third-order stream in southern Ontario. Using UV spectroscopy, measures of spectral slopes, aromaticity, and A 254/A 365 ratios (molecular weight) were obtained. Temporal changes in these measures were consistent with watershed processes such as shedding of leaf litter in the fall, and photochemical and biofilm influence in the spring and summer. The fluorescence index (a measure of relative DOM source) suggested that at the surface and in the downwelling Zone, DOM microbial sources increased with depth in the sediment, regardless of the season. Excitation–emission matrices (EEMs) showed seasonally distinct, protein-like DOM components of bacterial origin that were stronger in the fall. Leachates from specific allochthonous DOM sources—leaf litter from Betula papyrifera (white birch) and Thuja occidentalis (white cedar)—and an autochthonous source, biofilm, were isolated and incubated with unfiltered surface water. EEMs from these leachates indicated that these sources could indeed help explain observed patterns of DOM in surface and subsurface waters. These results suggest that although DOM sources were relatively constant, biogeochemical processing within the Hyporheic Zone resulted a DOM pool that was temporally dynamic and altered the nature of organic matter transported downstream into lakes and rivers.
-
perspectives and predictions on the microbial ecology of the Hyporheic Zone
Freshwater Biology, 1999Co-Authors: Richard G. Storey, Roberta R. Fulthorpe, Dudley D WilliamsAbstract:1. Studies of Hyporheic microbial ecology have suggested an important role for Hyporheic microbial processes in stream ecosystem functioning. Using evidence from microbial communities in other aquatic habitats, some predictions are made concerning the diversity of microbial types and microbial processes likely to occur in the Hyporheic Zone, and the relative importance of these various types to the Hyporheic ecosystem. 2. It is predicted that the biofilm growth form of interstitial micro-organisms will create a variety of microniches, allowing coexistence of a great diversity of microbial types, and promoting the activity of some otherwise poor competitors. It is further predicted that the confluence of reduced groundwaters and aerobic surface waters will favour chemolithotrophic processes in the Hyporheic Zone, but that these will contribute significantly to Hyporheic production only if surface water is very low in dissolved organic carbon, or the groundwater is extremely reduced, such as by the influence of riparian wetlands. A variety of anaerobic respiratory pathways, such as nitrate, ferric ion, sulphate and even methanogenic respiration will be employed in the Hyporheic Zone, with biofilm dynamics permitting these to occur even in aerobic sediments. Anaerobic pathways may account for a significant proportion of total Hyporheic organic matter mineralization. 3. The role of fungi in Hyporheic dynamics is, as yet, almost completely unstudied. However, it is expected that they will be important in breaking down buried particulate organic matter (POM), which may account for a large proportion of total stream POM. 4. Physicochemical conditions in Hyporheic sediments appear to be highly heterogeneous, and this heterogeneity may be very important in the cycling of certain nutrients, especially nitrogen, which involves a series of steps requiring different conditions. 5. Various new techniques are now available by which biofilm dynamics and in situ microbial processes may be measured. Studies are recommended of intact microbial communities both at the microscale of the biofilm and at the scale of the heterogeneities occurring in Hyporheic sediments. Studies are needed that measure actual rates of microbial processes under in situ conditions.
Timothy Sickbert - One of the best experts on this subject based on the ideXlab platform.
-
stream water bypass through a meander neck laterally extending the Hyporheic Zone
Hydrogeology Journal, 2006Co-Authors: Eric W Peterson, Timothy SickbertAbstract:A meander lobe neck diverts stream water into a Hyporheic flow path adjacent to a low gradient stream, Little Kickapoo Creek, Illinois, USA. Hyporheic processes have been well-documented in surface water–groundwater mixing Zones underlying and directly adjacent to streams. Alluvial aquifers underlying meander necks provide a further extension of the Hyporheic Zone. Hydraulic head and temperature data, collected from a set of wells across a meander neck, show stream water moves through the meander neck. The hydraulic gradient across the meander neck (0.006) is greater than the stream gradient (0.003) between the same points, driving the bypass. Rapid subsurface response to elevated stream stage shows a hydraulic connection between the stream and the alluvial aquifer. Temperature data and a Peclet number (Pe) of 43.1 indicate that thermal transport is dominated by advection from the upstream side to the downstream side of the meander neck. The temperature observed within the alluvial aquifer correlates with seasonal temperature variation. Together, the pressure and temperature data indicate that water moves across the meander neck. The inflow of stream water through the meander neck suggests that the meander system may host biogeochemical Hyporheic Zone processes.
-
stream water bypass through a meander neck laterally extending the Hyporheic Zone
Hydrogeology Journal, 2006Co-Authors: Eric W Peterson, Timothy SickbertAbstract:A meander lobe neck diverts stream water into a Hyporheic flow path adjacent to a low gradient stream, Little Kickapoo Creek, Illinois, USA. Hyporheic process- es have been well-documented in surface water-ground- water mixing Zones underlying and directly adjacent to streams. Alluvial aquifers underlying meander necks provide a further extension of the Hyporheic Zone. Hydraulic head and temperature data, collected from a set of wells across a meander neck, show stream water moves through the meander neck. The hydraulic gradient across the meander neck (0.006) is greater than the stream gradient (0.003) between the same points, driving the bypass. Rapid subsurface response to elevated stream stage shows a hydraulic connection between the stream and the alluvial aquifer. Temperature data and a Peclet number (Pe) of 43.1 indicate that thermal transport is dominated by advection from the upstream side to the downstream side of the meander neck. The temperature observed within the alluvial aquifer correlates with
Evan V Arntzen - One of the best experts on this subject based on the ideXlab platform.
-
multi omics comparison reveals metabolome biochemistry not microbiome composition or gene expression corresponds to elevated biogeochemical function in the Hyporheic Zone
Science of The Total Environment, 2018Co-Authors: Emily B Graham, Evan V Arntzen, Alex R Crump, David W Kennedy, Sarah J Fansler, Samuel O Purvine, Carrie D Nicora, William C Nelson, Malak M Tfaily, James C StegenAbstract:Biogeochemical hotspots are pervasive at terrestrial-aquatic interfaces, particularly within groundwater-surface water mixing Zones (Hyporheic Zones), and they are critical to understanding spatiotemporal variation in biogeochemical cycling. Here, we use multi 'omic comparisons of hotspots to low-activity sediments to gain mechanistic insight into Hyporheic Zone organic matter processing. We hypothesized that microbiome structure and function, as described by metagenomics and metaproteomics, would distinguish hotspots from low-activity sediments by shifting metabolism towards carbohydrate-utilizing pathways and elucidate discrete mechanisms governing organic matter processing in each location. We also expected these differences to be reflected in the metabolome, whereby hotspot carbon (C) pools and metabolite transformations therein would be enriched in sugar-associated compounds. In contrast to expectations, we found pronounced phenotypic plasticity in the Hyporheic Zone microbiome that was denoted by similar microbiome structure, functional potential, and expression across sediments with dissimilar metabolic rates. Instead, diverse nitrogenous metabolites and biochemical transformations characterized hotspots. Metabolomes also corresponded more strongly to aerobic metabolism than bulk C or N content only (explaining 67% vs. 42% and 37% of variation respectively), and bulk C and N did not improve statistical models based on metabolome composition alone. These results point to organic nitrogen as a significant regulatory factor influencing Hyporheic Zone organic matter processing. Based on our findings, we propose incorporating knowledge of metabolic pathways associated with different chemical fractions of C pools into ecosystem models will enhance prediction accuracy.
-
multi omics comparison reveals metabolome biochemistry not microbiome composition or gene expression corresponds to elevated biogeochemical function in the Hyporheic Zone
bioRxiv, 2018Co-Authors: Emily B Graham, Evan V Arntzen, Alex R Crump, David W Kennedy, Sarah J Fansler, Samuel O Purvine, Carrie D Nicora, William C Nelson, Malak M Tfaily, James C StegenAbstract:Biogeochemical hotspots are pervasive at terrestrial-aquatic interfaces, particularly within groundwater-surface water mixing Zones (Hyporheic Zones), and they are critical to understanding spatiotemporal variation in biogeochemical cycling. Here, we use multi omic comparisons of hotspots to low-activity sediments to gain mechanistic insight into Hyporheic Zone organic matter processing. We hypothesized that microbiome structure and function, as described by metagenomics and metaproteomics, would distinguish hotspots from low-activity sediments through a shift towards carbohydrate-utilizing metabolic pathways and elucidate discrete mechanisms governing organic matter processing in each location. We also expected these differences to be reflected in the metabolome, whereby hotspot carbon (C) pools and metabolite transformations therein would be enriched in sugar-associated compounds. In contrast to expectations, we found pronounced phenotypic plasticity in the Hyporheic Zone microbiome that was denoted by similar microbiome structure, functional potential, and expression across sediments with dissimilar metabolic rates. Instead, diverse nitrogenous metabolites and biochemical transformations characterized hotspots. Metabolomes also corresponded more strongly to aerobic metabolism than bulk C content only (explaining 67% vs. 42% of variation), and bulk C did not improve statistical models based on metabolome composition alone. These results point to organic nitrogen as a significant regulatory factor influencing Hyporheic Zone organic matter processing. Based on our findings, we propose incorporating knowledge of metabolic pathways associated with different chemical fractions of C pools into ecosystem models will enhance prediction accuracy.
-
effect of rapidly changing river stage on uranium flux through the Hyporheic Zone
Ground Water, 2007Co-Authors: Brad G Fritz, Evan V ArntzenAbstract:Measurement of ground water/surface water interaction within the Hyporheic Zone is increasingly recognized as an important aspect of subsurface contaminant fate and transport. Understanding the interaction between ground water and surface water is critical in developing a complete conceptual model of contaminant transport through the Hyporheic Zone. At the Hanford Site near Richland, Washington, ground water contaminated with uranium discharges to the Columbia River through the Hyporheic Zone. Ground water flux varies according to changes in hydraulic gradient caused by fluctuating river stage, which changes in response to operation of dams on the Columbia River. Piezometers and continuous water quality monitoring probes were installed in the Hyporheic Zone to provide long-term, high-frequency measurement of hydraulic gradient and estimated uranium concentrations. Subsequently, the flux of water and uranium was calculated for each half-hour time period over a 15-month study period. In addition, measurement of water levels in the near-shore unconfined aquifer enhanced the understanding of the relationship between river stage, aquifer elevation, and uranium flux. Changing river stage resulted in fluctuating hydraulic gradient within the Hyporheic Zone. Further, influx of river water caused lower uranium concentrations as a result of dilution. The methods employed in this study provide a better understanding of the interaction between surface and ground water in a situation with a dynamically varying vertical hydraulic gradient and illustrate how the combination of relatively standard methods can be used to derive an accurate estimation of water and contaminant flux through the Hyporheic Zone.
-
investigation of the Hyporheic Zone at the 300 area hanford site
2007Co-Authors: Brad G Fritz, Nancy P Kohn, Tyler J Gilmore, Doug Mcfarland, Evan V Arntzen, Rob D Mackley, Gregory W Patton, Donaldo P Mendoza, Amoret L BunnAbstract:The Remediation Task of the Science and Technology (S&T) Project is intended to provide research to meet several objectives concerning the discharge of groundwater contamination into the river at the 300 Area of the Hanford Site. This report serves to meet the research objectives by developing baseline data for future evaluation of remedial technologies, evaluating the effects changing river stage on near-shore groundwater chemistry, improving estimates of contaminant flux to the river, providing estimates on the extent of contaminant discharge areas along the shoreline, and providing data to support computer models used to evaluate remedial alternatives. This report summarizes the activities conducted to date and provides an overview of data collected through July 2006. Recent geologic investigations (funded through other U. S. Department of Energy (DOE) programs) have provided a more complete geologic interpretation of the 300 Area and a characterization of the vertical extent of uranium contamination. Extrapolation of this geologic interpretation into the Hyporheic Zone is possible, but there is little data to provide corroboration. Penetration testing was conducted along the shoreline to develop evidence to support the extrapolation of the mapping of the geologic facies. In general, this penetration testing provided evidence supporting the extrapolation of themore » most recent geologic interpretation, but it also provided some higher resolution detail on the shape of the layer than constrains contaminant movement. Information on this confining layer will provide a more detailed estimate of the area of river bed that has the potential to be impacted by uranium discharge to the river from groundwater transport. Water sampling in the Hyporheic Zone has provided results that illustrate the degree of mixing that occurs in the Hyporheic Zone. Uranium concentrations measured at individual sampling locations can vary by several orders of magnitude depending on the river and near-shore aquifer elevations. It is shown in this report that the concentrations of all the measured constituents in water samples collected from the Hyporheic Zone vary according to the ratio of groundwater and river water in the sample. One important aspect of this is that specific conductance provides a sensitive indicator of the relative contribution of groundwater and river water in a particular sample. This is because of the large difference is specific conductance of groundwater (~400 μS/cm) and river water (~130 μS/cm). It appears that in the Hyporheic Zone, advection of contaminates occurs very quickly, and variations in concentrations are a function of dilution rather than any chemistry effects caused by the difference in water chemistry between groundwater and river water.« less
-
investigation of the Hyporheic Zone at the 300 area hanford site
2007Co-Authors: Brad G Fritz, Nancy P Kohn, Tyler J Gilmore, Doug Mcfarland, Evan V Arntzen, Rob D Mackley, Gregory W Patton, Donaldo P Mendoza, Amoret L BunnAbstract:The Remediation Task of the Science and Technology (S&T) Project is intended to provide research to meet several objectives concerning the discharge of groundwater contamination into the river at the 300 Area of the Hanford Site. This report serves to meet the research objectives by developing baseline data for future evaluation of remedial technologies, evaluating the effects changing river stage on near-shore groundwater chemistry, improving estimates of contaminant flux to the river, providing estimates on the extent of contaminant discharge areas along the shoreline, and providing data to support computer models used to evaluate remedial alternatives. This report summarizes the activities conducted to date and provides an overview of data collected through July 2006. Recent geologic investigations (funded through other U. S. Department of Energy (DOE) programs) have provided a more complete geologic interpretation of the 300 Area and a characterization of the vertical extent of uranium contamination. Extrapolation of this geologic interpretation into the Hyporheic Zone is possible, but there is little data to provide corroboration. Penetration testing was conducted along the shoreline to develop evidence to support the extrapolation of the mapping of the geologic facies. In general, this penetration testing provided evidence supporting the extrapolation of themore » most recent geologic interpretation, but it also provided some higher resolution detail on the shape of the layer than constrains contaminant movement. Information on this confining layer will provide a more detailed estimate of the area of river bed that has the potential to be impacted by uranium discharge to the river from groundwater transport. Water sampling in the Hyporheic Zone has provided results that illustrate the degree of mixing that occurs in the Hyporheic Zone. Uranium concentrations measured at individual sampling locations can vary by several orders of magnitude depending on the river and near-shore aquifer elevations. It is shown in this report that the concentrations of all the measured constituents in water samples collected from the Hyporheic Zone vary according to the ratio of groundwater and river water in the sample. One important aspect of this is that specific conductance provides a sensitive indicator of the relative contribution of groundwater and river water in a particular sample. This is because of the large difference is specific conductance of groundwater (~400 μS/cm) and river water (~130 μS/cm). It appears that in the Hyporheic Zone, advection of contaminates occurs very quickly, and variations in concentrations are a function of dilution rather than any chemistry effects caused by the difference in water chemistry between groundwater and river water.« less
Eric W Peterson - One of the best experts on this subject based on the ideXlab platform.
-
stream water bypass through a meander neck laterally extending the Hyporheic Zone
Hydrogeology Journal, 2006Co-Authors: Eric W Peterson, Timothy SickbertAbstract:A meander lobe neck diverts stream water into a Hyporheic flow path adjacent to a low gradient stream, Little Kickapoo Creek, Illinois, USA. Hyporheic processes have been well-documented in surface water–groundwater mixing Zones underlying and directly adjacent to streams. Alluvial aquifers underlying meander necks provide a further extension of the Hyporheic Zone. Hydraulic head and temperature data, collected from a set of wells across a meander neck, show stream water moves through the meander neck. The hydraulic gradient across the meander neck (0.006) is greater than the stream gradient (0.003) between the same points, driving the bypass. Rapid subsurface response to elevated stream stage shows a hydraulic connection between the stream and the alluvial aquifer. Temperature data and a Peclet number (Pe) of 43.1 indicate that thermal transport is dominated by advection from the upstream side to the downstream side of the meander neck. The temperature observed within the alluvial aquifer correlates with seasonal temperature variation. Together, the pressure and temperature data indicate that water moves across the meander neck. The inflow of stream water through the meander neck suggests that the meander system may host biogeochemical Hyporheic Zone processes.
-
stream water bypass through a meander neck laterally extending the Hyporheic Zone
Hydrogeology Journal, 2006Co-Authors: Eric W Peterson, Timothy SickbertAbstract:A meander lobe neck diverts stream water into a Hyporheic flow path adjacent to a low gradient stream, Little Kickapoo Creek, Illinois, USA. Hyporheic process- es have been well-documented in surface water-ground- water mixing Zones underlying and directly adjacent to streams. Alluvial aquifers underlying meander necks provide a further extension of the Hyporheic Zone. Hydraulic head and temperature data, collected from a set of wells across a meander neck, show stream water moves through the meander neck. The hydraulic gradient across the meander neck (0.006) is greater than the stream gradient (0.003) between the same points, driving the bypass. Rapid subsurface response to elevated stream stage shows a hydraulic connection between the stream and the alluvial aquifer. Temperature data and a Peclet number (Pe) of 43.1 indicate that thermal transport is dominated by advection from the upstream side to the downstream side of the meander neck. The temperature observed within the alluvial aquifer correlates with
Catherine M Febria - One of the best experts on this subject based on the ideXlab platform.
-
bacterial community dynamics in the Hyporheic Zone of an intermittent stream
The ISME Journal, 2012Co-Authors: Roberta R. Fulthorpe, Catherine M Febria, Paul Beddoes, Dudley D WilliamsAbstract:The dynamics of in situ bacterial communities in the Hyporheic Zone of an intermittent stream were described in high spatiotemporal detail. We assessed community dynamics in stream sediments and interstitial pore water over a two-year period using terminal-restriction fragment length polymorphism. Here, we show that sediments remained saturated despite months of drought and limited hydrologic connectivity. The intermittency of stream surface water affected interstitial pore water communities more than Hyporheic sediment communities. Seasonal changes in bacterial community composition was significantly associated with water intermittency, phosphate concentrations, temperature, nitrate and dissolved organic carbon (DOC) concentrations. During periods of low- to no-surface water, communities changed from being rich in operational taxonomic units (OTUs) in isolated surface pools, to a few OTUs overall, including an overall decline in both common and rare taxa. Individual OTUs were compared between porewater and sediments. A total of 19% of identified OTUs existed in both porewater and sediment samples, suggesting that bacteria use Hyporheic sediments as a type of refuge from dessication, transported through hydrologically connected pore spaces. Stream intermittency impacted bacterial diversity on rapid timescales (that is, within days), below-ground and in the Hyporheic Zone. Owing to the coupling of intermittent streams to the surrounding watershed, we stress the importance of understanding connectivity at the pore scale, consequences for below-ground and above-ground biodiversity and nutrient processing, and across both short- and long-time periods (that is, days to months to years).