A5018308160- Soil and Water Nutrient Dynamics
- Fish Ecology and Management Studies
- Hydrology and Watershed Management Studies
- Freshwater macroinvertebrate diversity and ecology
- Aquatic Ecosystems and Phytoplankton Dynamics
- Water Quality and Resources Studies
- Hydrology and Sediment Transport Processes
- Aquatic Invertebrate Ecology and Behavior
- Groundwater and Isotope Geochemistry
- Marine and coastal ecosystems
- Diatoms and Algae Research
- Groundwater flow and contamination studies
- Urban Stormwater Management Solutions
- Water Quality and Pollution Assessment
- Water Quality Monitoring and Analysis
- Biocrusts and Microbial Ecology
- Animal Ecology and Behavior Studies
- Ecosystem dynamics and resilience
- Wastewater Treatment and Nitrogen Removal
- Radioactive contamination and transfer
- Mine drainage and remediation techniques
- Plant and animal studies
- Microfluidic and Bio-sensing Technologies
- American Environmental and Regional History
- Fecal contamination and water quality
Murray State University
2008-2023
Oak Ridge National Laboratory
1999
University of Michigan
1988
NOAA Great Lakes Environmental Research Laboratory
1988
We assembled data from a global network of automated lake observatories to test hypotheses regarding the drivers ecosystem metabolism. estimated daily rates respiration and gross primary production (GPP) for up full year in each lake, via maximum likelihood fits free‐water metabolism model continuous high‐frequency measurements dissolved oxygen concentrations. Uncertainties were determined by bootstrap analysis, allowing lake‐days with poorly constrained rate estimates be down‐weighted...
We used nondisruptive, whole-stream methods to measure hydraulic characteristics, ecosystem metabolism, and phosphorus cycling in the west fork of Walker Branch (WB), Tennessee Hugh White Creek (HWC), North Carolina. Although similar many their hydrological chemical transient storage zone volume HWC was relatively large (∼1.5 times that flowing water zone), whereas WB small (∼0.1 zone). Both streams were highly heterotrophic (gross primary production: total respiration ratios <0.1), although...
Streambed temperature patterns were measured in three riffles of a northern Michigan (USA) warmwater river using 95-cm long stainless steel probes. In with uniform small particle substrata, suggested that streamwater infiltration occurred at the head riffles, affecting substrate temperatures as much 50 cm deep. At downstream end cool water was nearer streambed surface. Temperature very irregular when large rocks and on bed. These data also suggest may be useful tool determining presence...
Interstitial temperature and chemistry were examined longitudinally with depth in a hyporheic zone beneath riffle–pool sequence of third-order, sand-bottom river northern Michigan (USA). Longitudinal patterns compared surface groundwater chemistries at the site over 10-km length river. water was more characteristic upstream end downstream end. Hyporheic longitudinal occurred for temperature, chloride, silica, soluble reactive phosphorus, winter dissolved oxygen. Dissolved organic carbon...
SUMMARY 1. We monitored streamwater and streambed sediment porewaters from White Clay Creek (WCC), SE Pennsylvania, for dissolved organic carbon (DOC), oxygen (DO) conductivity to investigate matter processing within the hyporheic zone. Dissolved DO concentrations were higher in than and, many cases, continued diminish with increasing depth into streambed. 2. Hydrological exchange data demonstrated that permeability of stream bed declines constrains downwelling, effectively isolating >30...
A case study of hyporheic research in a northern Michigan river is presented to illustrate some potential effects subsurface hydrology on microbial ecology. Hydrologic flow between downwelling and an upwelling zone beneath riffle-pool sequence promoted hyporheic-groundwater interaction differentiated regions increased bacterial activity, production, turnover time, responsiveness dissolved organic carbon enrichment. Large gaps knowledge exist the structure function fungal, bacterial,...
Twenty conservative tracer injections were carried out in the same reach of a small woodland stream order to determine how variation discharge and leaf accumulation affect hydraulic parameters. The made at various rates ranging from 2·6 40 l/s. Five during late autumn, when there large accumulations leaves stream. Estimates parameters by fitting transient storage solute transport model concentration profiles. Velocity increased almost linearly with increasing discharge, indicating decline...
We studied trends in nutrient cycling and periphyton characteristics (biomass, species composition, productivity, content) along longitudinal gradients laboratory streams to test the hypothesis that upstream-downstream linkages produce distinct patterns stream ecosystems. Periphyton communities were grown under uniform light flow conditions two 88-m-long created by connecting four channel segments (each 0.3 m wide 22 long) series. At end of 8 wk, large declines streamwater N P concentrations...
Relationships among stream surface water (9-km reach), substream hyporheic (10-m pool-riffle-pool and riparian groundwater (single site) biogeochemical patterns were examined in four seasons (1989-1990) a temperate ecosystem (Michigan, USA). Surface concentrations of chloride, dissolved organic carbon (DOC), chlorophyll-a exceeded those during most sampling periods. Groundwater silica (SiO 2 ), soluble reactive phosphorus (SRP), nitrate+nitrite (NO 3 -N), ammonium (NH 4 -N) generally higher...
Bacterial biomass, activity, and production were examined within the hyporheic zone of a sandy-bed, north-temperate stream over three seasons. Date (November, February, May), (upwelling, downwelling), depth (10 cm, 50 cm into bed) significant main effects on bacterial variables. Biomass significantly higher in May than during November generally at 10 depth. Activity was downwelling followed by minor peak May. Production 10-fold that upwelling zone. Response bacteria to DOC enrichments...
Abstract Phytoplankton biomass and production regulates key aspects of freshwater ecosystems yet its variability subsequent predictability is poorly understood. We estimated within‐lake variation in using high‐frequency chlorophyll fluorescence data from 18 globally distributed lakes. tested how at monthly, daily, hourly scales was related to wind, water temperature, radiation within lakes as well productivity physical attributes among Within lakes, monthly dominated, but combined daily were...
Eutrophication of inland waters is expected to increase the frequency and severity harmful algal blooms (HABs). Toxin-production associated with HABs has negative effects on human health aquatic ecosystem functioning. Despite evidence that flagellates can ingest toxin-producing cyanobacteria, interactions between members microbial loop are underestimated in our understanding food web bloom dynamics. Physical allelopathic a mixotrophic flagellate (Cryptomonas sp.) two strains cyanobacteria...
Abstract Spatial synchrony is defined by related fluctuations through time in population abundances measured at different locations. The degree of relatedness typically declines with increasing distance between sampling Standard approaches for assessing assume isotropy space and uniformity across timescales analysis, but it now known that spatial variability timescale structure dynamics are common features. We tested the patterns freshwater plankton Kentucky Lake, U.S.A. also evaluated...
Spatial synchrony in population dynamics is a ubiquitous ecological phenomenon that can result from predator–prey interactions, synchronized environmental variation (Moran effects), or dispersal. Of these, dispersal historically has been the least well studied natural systems, partly because of difficulty quantifying situ. We hypothesized routes plankton were based on major and consistent water current movements Kentucky Lake, large reservoir western Kentucky, USA. Then, using 26‐year time...
ABSTRACT Nutrient patterns were examined spatially and temporally from 1989 to 1998 in Kentucky Lake U.S.A., the largest mainstem reservoir on Tennessee River system. Nutrients included NO3 −-N, NH4 +-N, PO4 −, SiO2, SO4 −2, Cl−. Seasonal most nutrient concentrations described well by cosine functions. descriptions had less variance than discharge related of concentrations, possibly due regulation discharge. Differing land-use practices either side associated with significantly different...
We have developed and implemented a summary field exercise for an introductory hydrogeology course without laboratory section. This builds on lectures problem sets that use pre-existing data. During one day in April, students measure hydraulic heads, stream spring flow, stream-bed seepage within the rural watershed of third-order perennial western Kentucky. Students calculate net specific discharge at various scales, map groundwater flow watershed, vertical gradients mouth where enters...
Two hundred eighty-two taxa of diatoms (Bacillariophyta) were identified from composited benthic samples collected at 16 sites on the Little River in western Kentucky 2000 and 2003. The basin is heavily impacted by non-point source pollution consisting high nutrient inputs siltation agricultural urban runoff. Pennate dominated flora comprising >96% total throughout basin. Commonly occurring pennate species included Achnanthidium minutissimum, Amphora perpusilla, Cocconeis placentula var....