Adjacent Streams Research Articles

Landslide-induced iron mobilisation shapes benthic accumulation of nutrients, trace metals and REE fractionation in an oligotrophic alpine stream

Large alpine landslides that entrain substantial organic material below the water table and create suspended floodplains may have long-term consequences for the mobilisation of redox sensitive elements, such as Fe, into streamwaters. In turn, the cycling of iron in aquatic systems can influence the fate of nutrients, alter primary productivity, enhance accumulation of trace metals and induce fractionation of rare earth elements (REE). In this study we examine a reach of a pristine oligotrophic alpine stream bracketing a 30year-old landslide and explore the consequences of landslide-induced Fe mobilisation for aqueous geochemistry and the composition of benthic stream cobble biofilm. Elevated Fe2+ and Mn in landslide zone stream waters reflect inputs of circumneutral groundwater from the landslide debris-zone floodplain. Geochemical characteristics are consistent with reductive dissolution being a primary mechanism of Fe2+ and Mn mobilisation. Stream cobble biofilm in the landslide zone is significantly (P<0.01) enriched in poorly crystalline Fe(III) (∼10–400 times background) and Mn (∼15–150 times background) (1M HCl extractable; Fe(III)Ab). While the landslide zone accounts for less than ∼9% of the total stream length, we estimate it is responsible for approximately 60–80% of the stream’s benthic biofilm load of poorly crystalline Fe(III) and Mn. Biofilm Fe(III) precipitates are comprised mainly of ferrihydrite, lepidocrocite and an organic-Fe species, while precipitate samples collected proximal to hyporheic seeps contain abundant sheath structures characteristic of the neutrophilic Fe(II)-oxidising bacteria Leptothrix spp. Stream-cobble Fe(III)-rich biofilm is accumulating PO43− (∼3–30 times background) and behaving as a preferential substrate for photosynthetic periphyton, with benthic PO43−, chlorophyll a, organic carbonHCl and total N all significantly positively correlated with Fe(III)Ab and significantly elevated within the landslide zone (P<0.01). P K-edge XANES indicates P is associated with both ferric and Ca-phosphate minerals, while SEM-EDX elemental mapping of Fe(III) precipitates reveal strong spatial associations between P, Ca and Fe. Cobble Fe(III)-rich biofilm is also sorbing and accumulating multiple trace metals and REE. Within the landslide zone there are significant (P<0.01) enrichments (up to ∼10–100 times background) for most trace metals examined here and metals display significant positive linear correlations with Fe(III)Ab on a log transformed basis. Stream cobble biofilm also exhibits distinct REE fractionation along the flow path, with light REE (La, Ce, Nd, Pr) preferentially partitioning to the Fe(III) and Mn-rich biofilm within the landslide zone. Accumulation of PO43− and trace metals in this relatively environmentally labile form may have implications for their bioavailability and downstream transport, but further research is required to assess possible ecological consequences. This study demonstrates the potential for large alpine landslides to encourage reach-scale circumneutral Fe mobilisation in adjacent streams, thereby shaping multiple aspects of benthic stream geochemistry for many years after the landslide event itself.

A continuous flow microfluidic calorimeter: 3-D numerical modeling with aqueous reactants

A computational analysis of the reacting flow field, species diffusion and heat transfer processes with thermal boundary layer effects in a microchannel reactor with a coflow configuration was performed. Two parallel adjacent streams of aqueous reactants flow along a wide, shallow, enclosed channel in contact with a substrate, which is affixed to a temperature controlled plate. The Fluent computational fluid dynamics package solved the Navier–Stokes, mass transport and energy equations. The energy model, including the enthalpy of reaction as a nonuniform heat source, was validated by calculating the energy balance at several control volumes in the microchannel. Analysis reveals that the temperature is nearly uniform across the channel thickness, in the direction normal to the substrate surface; hence, measurements made by sensors at or near the surface are representative of the average temperature. Additionally, modeling the channel with a glass substrate and a silicone cover shows that heat transfer is predominantly due to the glass substrate. Finally, using the numerical results, we suggest that a microcalorimeter could be based on this configuration, and that temperature sensors such as optical nanohole array sensors could have sufficient spatial resolution to determine enthalpy of reaction.

Recreational stream crossing effects on sediment delivery and macroinvertebrates in southwestern Virginia, USA.

Trail-based recreation has increased over recent decades, raising the environmental management issue of soil erosion that originates from unsurfaced, recreational trail systems. Trail-based soil erosion that occurs near stream crossings represents a non-point source of pollution to streams. We modeled soil erosion rates along multiple-use (hiking, mountain biking, and horseback riding) recreational trails that approach culvert and ford stream crossings as potential sources of sediment input and evaluated whether recreational stream crossings were impacting water quality based on downstream changes in macroinvertebrate-based indices within the Poverty Creek Trail System of the George Washington and Jefferson National Forest in southwestern Virginia, USA. We found modeled soil erosion rates for non-motorized recreational approaches that were lower than published estimates for an off-road vehicle approach, bare horse trails, and bare forest operational skid trail and road approaches, but were 13 times greater than estimated rates for undisturbed forests and 2.4 times greater than a 2-year old clearcut in this region. Estimated soil erosion rates were similar to rates for skid trails and horse trails where best management practices (BMPs) had been implemented. Downstream changes in macroinvertebrate-based indices indicated water quality was lower downstream from crossings than in upstream reference reaches. Our modeled soil erosion rates illustrate recreational stream crossing approaches have the potential to deliver sediment into adjacent streams, particularly where BMPs are not being implemented or where approaches are not properly managed, and as a result can negatively impact water quality below stream crossings.

Influence of a tributary stream on benthic communities in a Didymosphenia geminata impacted stream in the Sierra Nevada, USA

The freshwater stalked diatom Didymosphenia geminata can alter benthic community structure. However, the numbers of D. geminata that must be present to do this is not clear. Is it possible that benthic communities in streams with D. geminata are not altered? A comparison of benthic communities in two similar, adjacent streams (one with and one without D. geminata) was conducted to identify the effects of D. geminata presence on benthic community structure. An additional comparison was made below the confluence of the two streams to determine the influence of an unregulated tributary stream on the temporal and spatial patterns of potential impacts of D. geminata on benthic communities. Benthic algal biomass (chlorophyll a and ash-free dry weight) in the D. geminata stream (dominated by D. geminata and Achnanthidium spp. throughout study period) was an order of magnitude higher. High D. geminata growth altered the physical environment of the stream benthos resulting in fewer grazing invertebrates and greater densities of burrowing invertebrates such as Chironomidae and Oligochaeta. Below the confluence, benthic community structure became more similar to the non-D. geminata stream. Results show that extensive growth of D. geminata can alter benthic communities, however, an unregulated non-D. geminata tributary stream can assuage impacts and establish benthic community structure resembling the non-D. geminata tributary stream over a relatively short distance. This study provides insight into the extent and mechanisms by which growth of D. geminata affects benthic communities and helps determine the influence of tributary stream on D. geminata growth and patterns in benthic communities.

The delivery of dissolved organic carbon from a forested hillslope to a headwater stream in southeastern Pennsylvania, USA

AbstractRiparian soils, rich in organic carbon, act as a source of dissolved organic carbon (DOC) to the adjacent stream, but the hydrologic factors that control the delivery of DOC are not well characterized. A mechanistic two‐dimensional, variably saturated flow and reactive transport finite element model (FEM) was developed to explore both biodegradable DOC (BDOC) and refractory DOC (RDOC) delivery processes during storms for a hillslope transect in a southeastern Pennsylvania Piedmont watershed. The model indicated that DOC concentrations in outflow from a hillslope peaked on the falling limb of the discharge hydrograph, a temporal sequence consistent with a flushing hypothesis. Factors that control the lag time between the stream water peak discharge and peak DOC concentration were analyzed using a Monte Carlo simulation coupled with a multiple linear regression. The results are consistent with previous studies showing that the majority of DOC delivered to a stream during storms originates from the riparian zone. Further, the model suggests that the duration of the flood wave and hydraulic properties of the riparian soil play important roles in controlling the lag time between peak discharge and peak DOC concentration in outflow from a hillslope.

Study of the effects of single and multiple periodic droplet impingements on liquid film heat transfer

A study of heat transfer and film dynamics caused by single and multiple streams of impinging droplets using HFE-7100 as the cooling liquid under constant heat flux conditions is presented. Single and multiple streams of mono-dispersed droplets were produced using a piezoelectric droplet generator with the ability to adjust parameters such as droplet impingement frequency, droplet diameter, droplet velocity, and spacing between adjacent impinging droplet streams. In this study, a heater consisting of a thin layer of Indium Tin Oxide (ITO) as heating element, combined with a Zinc Selenide (ZnSe) substrate was used for characterizing the heat transfer behavior and hydrodynamic phenomena of impinged liquid films near or at the onset of critical heat flux (CHF). Film thickness inside the impact crater was measured using the Total Internal Reflection (TIR) technique. Hydrodynamic phenomena of the droplet impact craters were analyzed using a high speed imaging technique. Impact regimes of the impinging droplets were identified and classified, and their effects on heat transfer performance are discussed.The study supports the notion that forced convection is the main heat transfer mechanism inside the impact crater due mainly to the high frequency and periodic nature of droplet impingement. Furthermore, droplet impingement regimes such as spreading and splashing have been observed to play an important role in the overall heat transfer behavior. Spacing between adjacent impinging droplet streams is also an important factor in surface cooling when multiple droplet streams are used.

Hydrologic Controls on Nitrogen and Phosphorous Dynamics in Relict Oxbow Wetlands Adjacent to an Urban Restored Stream

AbstractAlthough wetlands are known to be sinks for nitrogen (N) and phosphorus (P), their function in urban watersheds remains unclear. We analyzed water and nitrate (NO3−) and phosphate (PO43−) dynamics during precipitation events in two oxbow wetlands that were created during geomorphic stream restoration in Baltimore County, Maryland that varied in the nature and extent of connectivity to the adjacent stream. Oxbow 1 (Ox1) received 1.6‐4.2% and Oxbow 2 (Ox2) received 4.2‐7.4% of cumulative streamflow during storm events from subsurface seepage (Ox1) and surface flow (Ox2). The retention time of incoming stormwater ranged from 0.2 to 6.7 days in Ox1 and 1.8 to 4.3 days in Ox2. Retention rates in the wetlands ranged from 0.25 to 2.74 g N/m2/day in Ox1 and 0.29 to 1.94 g N/m2/day in Ox2. Percent retention of the NO3−‐N load that entered the wetlands during the storm events ranged from 64 to 87% and 23 to 26%, in Ox1 and Ox2, respectively. During all four storm events, Ox1 and Ox2 were a small net source of dissolved PO43− to the adjacent stream (i.e., more P exited than entered the wetland), releasing P at a rate of 0.23‐20.83 mg P/m2/day and 3.43‐24.84 mg P/m2/day, respectively. N and P removal efficiency of the oxbows were regulated by hydrologic connectivity, hydraulic loading, and retention time. Incidental oxbow wetlands have potential to receive urban stream and storm flow and to be significant N sinks, but they may be sources of P in urban watersheds.

The contribution of estuary-resident life histories to the return of adult Oncorhynchus kisutch.

This study evaluated estuarine habitat use, life-history composition, growth and survival of four successive broods of coho salmon Oncoryhnchus kisutch in Salmon River, Oregon, U.S.A. Subyearling and yearling O. kisutch used restored and natural estuarine wetlands, particularly in the spring and winter. Stream-reared yearling smolts spent an average of 2 weeks in the estuary growing rapidly before entering the ocean. Emergent fry also entered the estuary in the spring, and some resided in a tidal marsh throughout the summer, even as salinities increased to >20. A significant portion of the summer stream-resident population of juvenile O. kisutch migrated out of the catchment in the autumn and winter and used estuary wetlands and adjacent streams as alternative winter-rearing habitats until the spring when they entered the ocean as yearling smolts. Passive integrated transponder (PIT) tag returns and juvenile life-history reconstructions from otoliths of returning adults revealed that four juvenile life-history types contributed to the adult population. Estuarine-associated life-history strategies accounted for 20-35% of the adults returning to spawn in the four brood years, indicating that a sizable proportion of the total O. kisutch production is ignored by conventional estimates based on stream habitat capacity. Juvenile O. kisutch responses to the reconnection of previously unavailable estuarine habitats have led to greater life-history diversity in the population and reflect greater phenotypic plasticity of the species in the U.S. Pacific Northwest than previously recognized.

Tracing sources of organic matter in adjacent urban streams having different degrees of channel modification

Urbanization and stream-channel modifications affect organic matter concentrations and quality in streams, by altering allochthonous organic matter input and in-stream transformation. This study uses multiple tracers (δ13C, δ15N, C/N ratio, and chlorophyll-a) to track sources of organic matter in two highly urbanized bayous in Houston (Texas, USA). Wastewater treatment plants (WWTPs) are located in headwaters of both bayous and contribute more than 75% to water flow. Low isotopic relatedness to natural end-members and enriched δ15N values suggest the influence of WWTPs on the composition of all organic matter fractions. The two bayous differ in degree of channel improvement resulting in different responses to hydrological conditions. During high flow conditions, the influence of terrestrial organic matter and sediment resuspension was much more pronounced in the Buffalo Bayou than in the concrete-lined White Oak Bayou. Particulate organic matter (POM) in White Oak Bayou had similar values of enriched δ15N in all subsegments, whereas in Buffalo Bayou, the degree of δ15N enrichment was less in the subsegments of the lower watershed. The difference in riparian zone contributions and interactions with sediments/soils was likely responsible for the compositional differences between the two bayous. Phytoplankton inputs were significantly higher in the bayous, especially in slow-flowing sections, relative to the reference sites, and elevated phytoplankton inputs accounted for the observed stable C isotope differences between FPOM and high molecular weight dissolved organic matter (HMW DOM). Relative to POM, HMW DOM in the bayous was similar to WWTP effluents and showed minor longitudinal variability in both streams suggesting that WWTPs contribute much of the DOM in the systems. Urbanization has a major influence on organic matter sources and quality in these urban water bodies and these changes seem further enhanced by stream channel modifications.

Science Walden: new horizons of combined ecological sanitation with separated urine/feces and treatment wetlands

A new engineering concept, designed with separated urine/feces and graywater recovery, was proposed, and the first steps in taking this concept from the planning stage to implementation have been taken using pilot experiments within a small village. The village employs ecological toilet, equipped with 24 h ventilation, and constructed treatment wetlands consisting of both vertical and horizontal subsurface wetlands for graywater recovery. The quality of recovered graywater was similar to that of the water found in the adjacent stream, which is a concept of zero discharge system with graywater. Separated urine, in either fresh or stored form, was diluted with collected rainwater and with reused water without any detergent from a sink, to be supplied to vegetable garden as fertilizer. Separated dried feces were composted in the garden for approximately 3 months and then used as fertilizer. Dried and composted feces, together with stored urine, were characterized in terms of microbial community using pyrosequencing, to identify the presence of any potential pathogens, in order to confirm the system provides safe hygiene. Hypothesized idea of a micro-algae farm within the village might be proposed with separated urine serving as nutrients for algae that could in turn be cultivated as biofuel (diesel) produced from extracted lipids of algae. Through this pilot village test, we have taken a great stride towards practical realization of experimental concepts, in the form of this new urban water management model with ecological sanitation.

Mountaintop Removal Mining and Catchment Hydrology

Mountaintop mining and valley fill (MTM/VF) coal extraction, practiced in the Central Appalachian region, represents a dramatic landscape-scale disturbance. MTM operations remove as much as 300 m of rock, soil, and vegetation from ridge tops to access deep coal seams and much of this material is placed in adjacent headwater streams altering landcover, drainage network, and topography. In spite of its scale, extent, and potential for continued use, the effects MTM/VF on catchment hydrology is poorly understood. Previous reviews focus on water quality and ecosystem health impacts, but little is known about how MTM/VF affects hydrology, particularly the movement and storage of water, hence the hydrologic processes that ultimately control flood generation, water chemistry, and biology. This paper aggregates the existing knowledge about the hydrologic impacts of MTM/VF to identify areas where further scientific investigation is needed. While contemporary surface mining generally increases peak and total runoff, the limited MTM/VF studies reveal significant variability in hydrologic response. Significant knowledge gaps relate to limited understanding of hydrologic processes in these systems. Until the hydrologic impact of this practice is better understood, efforts to reduce water quantity and quality problems and ecosystem degradation will be difficult to achieve.

Effect of Manure Application on Abundance of Antibiotic Resistance Genes and Their Attenuation Rates in Soil: Field-Scale Mass Balance Approach

The development of models for understanding antibiotic resistance gene (ARG) persistence and transport is a critical next step toward informing mitigation strategies to prevent the spread of antibiotic resistance in the environment. A field study was performed that used a mass balance approach to gain insight into the transport and dissipation of ARGs following land application of manure. Soil from a small drainage plot including a manure application site, an unmanured control site, and an adjacent stream and buffer zone were sampled for ARGs and metals before and after application of dairy manure slurry and a dry stack mixture of equine, bovine, and ovine manure. Results of mass balance suggest growth of bacterial hosts containing ARGs and/or horizontal gene transfer immediately following slurry application with respect to ermF, sul1, and sul2 and following a lag (13 days) for dry-stack-amended soils. Generally no effects on tet(G), tet(O), or tet(W) soil concentrations were observed despite the presence of these genes in applied manure. Dissipation rates were fastest for ermF in slurry-treated soils (logarithmic decay coefficient of -3.5) and for sul1 and sul2 in dry-stack-amended soils (logarithmic decay coefficients of -0.54 and -0.48, respectively), and evidence for surface and subsurface transport was not observed. Results provide a mass balance approach for tracking ARG fate and insights to inform modeling and limiting the transport of manure-borne ARGs to neighboring surface water.

Data processing for oscillatory pumping tests

Characterizing the subsurface is important for many hydrogeologic projects such as site remediation and groundwater resource exploration. Methods based on the analysis of conventional pumping tests have the notable disadvantage that at a certain distance, the signal is small relative to the noise due to the effects of recharge, pumping in neighboring wells, change in the level or adjacent streams, and other common disturbances. This work focuses on oscillatory pumping tests in which fluid is extracted for half a period, then reinjected. We discuss a major advantage of oscillatory pumping tests: small amplitude signals can be recovered from noisy data measured at observation wells and quantify the uncertainties in the estimates. We demonstrate results from a joint inversion of storativity and transmissivity. We conclude with an analysis of the duration of the initial transient, providing lower bounds on the length of elapsed time until the effects of the transient can be neglected.

Nitrate fate and transport through current and former depressional wetlands in an agricultural landscape, Choptank Watershed, Maryland, United States

Understanding local groundwater hydrology and geochemistry is critical for evaluating the effectiveness of wetlands at mitigating agricultural impacts on surface waters. The effectiveness of depressional wetlands at mitigating nitrate (NO₃) transport from fertilized row crops, through groundwater, to local streams was examined in the watershed of the upper Choptank River, a tributary of Chesapeake Bay on the Atlantic Coastal Plain. Hydrologic, geochemical, and water quality data were collected from January of 2008 through December of 2009 from surface waters and networks of piezometers installed in and around current or former depressional wetlands of three major types along a gradient of anthropogenic alteration: (1) natural wetlands with native vegetation (i.e., forested); (2) prior-converted croplands, which are former wetlands located in cultivated fields; and (3) hydrologically restored wetlands, including one wetland restoration and one shallow water management area. These data were collected to estimate the orientation of groundwater flow paths and likely interactions of groundwater containing NO₃ from agricultural sources with reducing conditions associated with wetlands of different types. Natural wetlands were found to have longer periods of soil saturation and reducing conditions conducive to denitrification compared to the other wetland types studied. Because natural wetlands are typically located in groundwater recharge areas along watershed divides, nitrogen (N) from nearby agriculture was not intercepted. However, these wetlands likely improve water quality in adjacent streams via dilution. Soil and geochemical conditions conducive to denitrification were also present in restored wetlands and prior-converted croplands, and substantial losses of agricultural NO₃ were observed in groundwater flowing through these wetland sediments. However, delivery of NO₃ from agricultural areas through groundwater to these wetlands resulting in opportunities for denitrification were limited, particularly where reducing conditions did not extend throughout the entire thickness of the surficial aquifer allowing NO₃ to pass conservatively beneath a wetland along deeper groundwater flow paths. The complexity of N fate and transport associated with depressional wetlands complicates the understanding of their importance to water quality in adjacent streams. Although depressional wetlands often contribute low NO₃ water to local streams, their effectiveness as landscape sinks, for N from adjacent agriculture varies with natural conditions, such as the thickness of the aquifer and the extent of reducing conditions. Measurement of such natural geologic, hydrologic, and geochemical conditions are therefore fundamental to understanding N mitigation in individual wetlands.

Dissolved radionuclide in the industrial effluent of uranium facilities, Jaduguda, India

Dissolved radionuclides in the effluent of uranium mining industry were studied. Activity concentrations of uranium and radium were estimated in effluent water from different uranium mines and mill tailings ponds. The concentrations of U and 226Ra in untreated effluent water were found to be elevated. The concentrations of dissolved radionuclides in the adjacent aquatic streams and river were found to be of low range. The waste management technology used for removal process of dissolved radionuclides in the Effluent Treatment Plant (ETP) is found to be effective.

EFFECTS OF SINGLE AND DOUBLE STREAMS OF DROPLET IMPINGEMENTS ON SURFACE COOLING

This paper explores the effects of high-frequency impinging droplets on surface cooling. A single stream of impinging droplets at different impact angles was studied by measuring the surface temperature distribution and characterizing the impact crater morphology under different heat flux conditions. Film thickness inside the droplet impact craters was measured to understand the relationship between film thickness and impact angle. Additionally, double streams of impinging droplets at different impact spacings and impact angles were investigated. The optimum spacing between adjacent droplet streams was found to reduce droplet-to-droplet collision and splashing, resulting in enhanced heat transfer and better use of the cooling fluid.

Dynamics and retreat of the Late Weichselian Kongsfjorden ice stream, NW Svalbard

Terrestrial cosmogenic nuclide dating in combination with detailed landform mapping in the Kongsfjordhallet area, NW Svalbard, have provided new insight on configuration, dynamics, and deglaciation of the Late Weichselian Kongsfjorden ice stream. The minimum Late Weichselian ice surface elevation in Kongsfjorden was >449 m a.s.l. indicating considerably thicker ice and a steeper surface gradient than earlier suggested. For the adjacent inter-ice stream area an even steeper surface slope is reconstructed. The glacial landforms, as well as the surface exposure ages of erratic boulders at different elevations, suggest a gradual lowering of the ice surface. Deglaciation of the higher elevations was probably underway by 20.0 ka. At ca 16.6 ka a large moraine complex (‘the Kongsfjorden moraine’) was deposited close to the fjord mouth. The shape of the moraines, the steep ice surface gradient, as well as the correlation to fine laminated clay lacking ice rafted debris deposited in the trough beyond the moraine suggest that ice dynamics switched from ice-stream behaviour to a slower flowing outlet (tidewater) glacier. A Younger Dryas or Early Holocene advance of local valley glaciers is shown by moraine lobes cross-cutting the Late Weichselian lateral moraines.

Nitrogen and carbon dynamics beneath on-site wastewater treatment systems in Pitt County, North Carolina

On-site wastewater treatment systems (OWS) are a potentially significant non-point source of nutrients to groundwater and surface waters, and are extensively used in coastal North Carolina. The goal of this study was to determine the treatment efficiency of four OWS in reducing total dissolved nitrogen (TDN) and dissolved organic carbon (DOC) concentrations before discharge to groundwater and/or adjacent surface water. Piezometers were installed for groundwater sample collection and nutrient analysis at four separate residences that use OWS. Septic tank effluent, groundwater, and surface water samples (from an adjacent stream) were collected four times during 2012 for TDN and DOC analysis and pH, temperature, electrical conductivity, and dissolved oxygen measurements. Treatment efficiencies from the tank to the groundwater beneath the drainfields ranged from 33 to 95% for TDN and 45 to 82% for DOC, although dilution accounted for most of the concentration reductions. There was a significant positive correlation between nitrate concentration and separation distance from trench bottom to water table and a significant negative correlation between DOC concentration and separation distance. The TDN and DOC transport (>15 m) from two OWS with groundwater saturated drainfield trenches was significant.

Microscale Adaptive Response of Charophytes of the Negev Desert, Israel: Species Divergences by AFLP

Genetic diversity of Chara populations found in Israeli Negev Desert streams was analyzed using amplified fragment length polymorphism (AFLP) in 31 individuals. The adjacent streams Avdat and Aqev were used as study sites in the Ein Avdat National Park. A Jaccard phylogenetic tree, based on 468 loci, showed clear separation between four Chara species: C. vulgaris, C. contraria, C. gymnophylla and Chara sp. The last two species served as out groups from the Northern Israel. In both C. vulgaris and C. contraria, genetic differences were found between the populations originating in the two streams: higher private loci number (80 vs. 24 in C. vulgaris and 58 vs. 25 in C. contraria) and polymorphic loci level (45% vs. 23% in C. vulgaris and 39% vs. 21% in C. contraria) were found in Avdat compared to Aqev. The genetic divergence revealed within and between the two streams is presumably adaptive and determined by natural selection associated with ecological stress. Sunlight intensity, water level and pH were found to be the main ecological variables associated with species clustering, through selection, in the varying ecology of the sampling stations along each of the streams. Evidence for gene flow between and within the streams was found using the structure analysis, suggesting that sampling sites condition is the regulating factor for oospores establishing, and hence, gene flow occurs more often between sampling sites with similar ecological conditions.

Stream Water and Groundwater Interaction Revealed by Temperature Monitoring in Agricultural Areas

Variations in stream water, streambed, adjacent stream sediment, and groundwater temperatures in the Haean basin, Korea were examined using time series analyses including auto-correlation, spectral density, and cross-correlation functions. The temperatures of the ambient air, stream water, streambed (depth = 10 cm), and adjacent stream sediment (depth = 10 cm) showed distinctive diurnal variations with long-term seasonal cooling trends, while groundwater temperature showed only a seasonal decreasing trend with little diurnal variations. Auto-correlations and spectral densities of the stream water, streambed, and sediment temperatures also revealed strong daily cyclical behaviors, with longer periodic cycles varying from weekly to monthly. Amplitudes and lag times of the streambed thermal signals were also affected by the hydraulic conductivities of the sediments. Lower hydraulic conductivity indicates a more attenuated and slower thermal response for the streambed. The calculated vertical water flow velocities of the streambed revealed that the investigated stream locations were under losing or gaining conditions, depending on the location and time.