Michelle Baker

Michelle Baker
Utah State University | USU · Department of Biology and the Ecology Center

PhD

About

78
Publications
10,483
Reads
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3,089
Citations
Additional affiliations
August 1999 - June 2015
Utah State University
Position
  • Faculty Member
August 1998 - August 1999
French National Centre for Scientific Research
Position
  • PostDoc Position
Education
September 1992 - May 1998

Publications

Publications (78)
Article
Full-text available
As human-dominated landscapes have expanded, the diversity of organic matter (OM) sources to rivers has increased, and knowledge of the composition and quality of these sources is lacking. It is important to characterize novel forms of OM that can affect retention, transport, and transformation of OM within watersheds. We collected fine particulate...
Article
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Lotic and lentic ecosystems are traditionally viewed as dominated by either benthic or water column processes. However, mid-sized rivers represent a transition zone where both benthic and water column processes may both contribute substantially to ecosystem dynamics. Ecosystem processes such as gross primary production (GPP), ecosystem respiration...
Article
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Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize back...
Article
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Stream bacterioplankton communities, a crucial component of aquatic ecosystems and surface water quality, are shaped by environmental selection (i.e., changes in taxa abundance associated with more or less favorable abiotic conditions) and passive dispersal (i.e., organisms’ abundance and distribution is a function of the movement of the water). Th...
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Bacteria in stream biofilms contribute to stream biogeochemical processes and are potentially sensitive to the substantial levels of pollution entering urban streams. To examine the effects of contaminants on stream biofilm bacteria in situ, we exposed growing biofilms to experimental additions of nutrients [nitrogen (N), phosphorus (P), and iron (...
Article
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Terrestrially derived organic matter (OM) is known to dominate the OM pool in reference watersheds. Urban watersheds are known to receive large OM loads compared to reference watersheds, but the proportion of terrestrial, autochthonous, and anthropogenic (e.g., wastewater effluent) sources of OM in urban watersheds remains unknown. Organic matter w...
Article
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Purpose: This paper presents findings of a quasi-experimental assessment to gauge the research productivity and degree of interdisciplinarity of research center outputs. Of special interest, we share an enriched visualization of research co-authoring patterns. Design/methodology/approach: We compile publications by 45 researchers in each of 1) the...
Article
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This article was unintentionally published twice in this journal, by the same authors.
Chapter
Solute dynamics describe the coupled physical, chemical, and biological processes that govern transport and transformations of materials dissolved in water. In this chapter, we describe empirical and modeling approaches to evaluate dynamics of conservative and reactive solutes in streams. Such approaches provide a foundation upon which studies of t...
Article
Along the river network, water, sediment, and nutrients are transported, cycled, and altered by coupled hydrological and biogeochemical processes. Our current understanding of the rates and processes controlling the cycling and removal of dissolved inorganic nutrients in river networks is limited due to a lack of empirical measurements in large, (n...
Article
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Water resources are increasingly impacted by growing human populations, land use, and climate changes, and complex interactions among biophysical processes. In an effort to better understand these factors in semiarid northern Utah, United States, we created a real-time observatory consisting of sensors deployed at aquatic and terrestrial stations t...
Article
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In response to water quality standard violations linked to excessive organic matter (OM) and a lack of sampling data informing the Total Maximum Daily Load (TMDL), an organic matter budget was created to quantify and identify sources of OM in the lower Jordan River (Salt Lake City, UT). By sampling dissolved, fine, and coarse particulate OM, as wel...
Article
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Urbanization substantially increases nitrogen (N) inputs and hydrologic losses relative to wildland ecosystems, although the fate of N additions to lawns and remnant grasslands remains contested. In montane semi-arid ecosystems, N cycling is often closely coupled to snowmelt (the dominant period of infiltration) and snow cover, which impact soil te...
Article
Full-text available
In response to water quality standard violations linked to excessive organic matter (OM) and a lack of sampling data informing the Total Maximum Daily Load (TMDL), an organic matter budget was created to quantify and identify sources of OM in the lower Jordan River (Salt Lake City, UT). By sampling dissolved, fine and coarse particulate OM, as well...
Article
The extent to which atmospheric nitrogen (N) deposition reflects land use differences and biogenic vs. fossil fuel reactive N sources remains unclear, yet represents a critical uncertainty in ecosystem N budgets. We compared N concentrations and isotopes in precipitation-event bulk (wet + dry) deposition across nearby valleys in northern Utah with...
Article
Despite the obvious hydrologic connection between streams and lakes in many regions of the world, rarely has this linkage been recognized conceptually. Most watersheds contain lakes or artificial reservoirs, so the linkages between these systems are widespread. Drawing on recent research in temperate and arctic regions, we describe a conceptual mod...
Article
Snowmelt dominates the hydrograph of many temperate montane streams, yet little work has characterized how stream water sources and nitrogen (N) dynamics vary across wildland to urban land use gradients in these watersheds. Across a third-order catchment in Salt Lake City, Utah, we asked where and when groundwater vs. shallow surface water inputs c...
Article
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Ecosystem metabolism, that is, gross primary productivity (GPP) and ecosystem respiration (ER), controls organic carbon (OC) cycling in stream and river networks and is expected to vary predictably with network position. However, estimates of metabolism in small streams outnumber those from rivers such that there are limited empirical data comparin...
Article
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Water quality monitoring programs across multiple disciplines use total suspended solids (TSS), and volatile suspended solids (VSS), to assess potential impairments of surface water and groundwater. While previous methods for instream filtering have been developed, the need for rapid, cost-effective, high volume sampling has increased with the need...
Article
Riparian plants incorporate nitrogen (N) from aquatic, terrestrial, and atmospheric sources, and their stable isotope compositions (d 15 N) may reflect land use impacts on N sources and transformations over scales of sites to watersheds. We surveyed leaf d 15
Article
Environmental science exists to seek solutions to problems related to human-nature interactions. Unfortunately, in many cases, environmental research findings are not effectively used because scientists are not able to convey their knowledge effectively to policy makers and the public, and/or because the questions they address are not directly link...
Article
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Nutrient transformation processes such as assimilation, dissimilatory transformation, and sorption to sediments are prevalent in benthic zones of headwater streams, but may also occur in the water column. The river continuum concept (RCC) predicts that water column processes become increasingly important with increasing stream size. We predicted th...
Article
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Urbanization, climate, and ecosystem change represent major challenges for managing water resources. Although water systems are complex, a need exists for a generalized representation of these systems to identify important components and linkages to guide scientific inquiry and aid water management. We developed an integrated Structure-Actor-Water...
Article
Rivers receive and process large quantities of terrestrial dissolved organic carbon (DOC). Biologically available (unstable) DOC leached from primary producers may stimulate (i.e., prime) the consumption of more stable terrestrially-derived DOC by heterotrophic microbes. We measured microbial DOC consumption (i.e., decay rates) from contrasting C s...
Article
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Stream ecosystem processes such as nutrient cycling may vary with stream position in the network. Using a scaling approach, we examined the relationship between stream size and nutrient uptake length, which represents the mean distance that a dissolved solute travels prior to removal from the water column. Ammonium (NH4+) uptake length increased pr...
Article
Full-text available
Stream ecosystem processes such as nutrient cycling may vary with stream position in the watershed. Using a scaling approach, we examined the relationship between stream size and nutrient uptake length, which represents the mean distance that a dissolved solute travels prior to removal from the water column. Ammonium uptake length increased proport...
Article
We used a stable isotope tracer to measure nitrogen (N) assimilation and transfer through Bull Trout Lake, a 0.3-km(2) mountain lake in Idaho, specifically to explore the relative importance of pelagic and benthic producers. (NO3-)-N-15 was added into the inflow stream above the lake during spring runoff and the resulting mass of tracer was measure...
Article
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Lakes within fluvial networks may affect dissolved organic matter (DOM) dynamics in streams by dampening spring DOM snowmelt flushing responses and/or by increasing summer DOM production. We assessed the temporal variability of dissolved organic carbon (DOC) concentration and DOM characteristics (specific ultraviolet absorbance (SUVA254); DOC:disso...
Article
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We used an in situ steady state 15N-labeled nitrate (15NO3-) and acetate (AcO-) well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as AcO-influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream. The experimental wells receiving conservative...
Article
Elevated nitrate (NO3⁻) concentrations can cause eutrophication, which may lead to harmful algal blooms, loss of habitat and reduction in biodiversity. Denitrification, a dissimilatory process that removes NO3⁻ mainly as dinitrogen gas (N2), is believed to be the dominant NO3⁻ removal pathway in aquatic ecosystems. Evidence suggests that a less wel...
Article
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Species diversity is important to ecosystems because of the increased probability of including species that are strong interactors and/or because multiple-species communities are more efficient at using resources due to synergisms and resource partitioning. Genetic diversity also contributes to ecosystem function through effects on primary producti...
Article
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Biogeochemical reactions associated with stream nitrogen cycling, such as nitrification and denitrification, can be strongly controlled by water and solute residence times in the hyporheic zone (HZ). We used a whole-stream steady state 15N-labeled nitrate (15NO3-) and conservative tracer (Cl-) addition to investigate the spatial and temporal physio...
Article
We examined transport time and substrate controls on hyporheic (HZ) nitrification and denitrification in an upland agricultural stream with a series of 15N tracer studies - whole-stream and in situ well-to-well steady-state 15NO3- and conservative tracer (Cl-) addition experiments. For the whole-stream experiment, we measured relevant solute, 15N i...
Article
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Hydrological and biogeochemical processes in stream reaches impact the downstream transport of nutrients. The output from one stream reach becomes the input for the next, leading to serial processing along stream networks. The shape of the uptake-concentration curve for each reach indicates in-stream biological uptake of nutrient. Combined with phy...
Article
Lakes can play a large role in structuring the chemical and physical templates of streams, yet they often are overlooked when stream function is evaluated. We examined how lakes within stream networks affect organic matter decomposition. We used a cotton-strip assay to evaluate cellulose decomposition potential (CDP) as loss of cotton-strip tensile...
Article
Full-text available
We used an in situ 15N-labeled nitrate (15NO3-) and acetate injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as acetate influences microbial denitrification in the hyporheic zone (HZ) of an upland (3rd-order) agricultural stream. A 48 h steady-state injection of a conservative tracer, chloride, and 15N...
Article
Nutrient cycling and export in streams and rivers should vary with flow regime, yet most studies of stream nutrient transformation do not include hydrologic variability. We used a stable isotope tracer of nitrogen (15N) to measure nitrate (NO3) uptake, storage, and export in a mountain stream, Spring Creek, Idaho, U.S.A. We conducted two tracer tes...
Article
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1] Application of transient storage models has become popular for characterizing hydrologic and biogeochemical processes in streams. The typical transient storage model represents exchange between the main channel and a single storage zone, essentially lumping together different exchange processes. Here we present a method to inform a transient sto...
Article
We evaluated how benthic algal assemblages that vary in composition, richness, and other diversity metrics; remove NO(3)-N from the water column of a mountain stream. Ecological theory and empirical studies suggest that ecosystem process rates should increase as richness increases because of niche separation or activity of dominant taxa. Accordingl...
Article
Given recent focus on large rivers as conduits for excess nutrients to coastal zones, their role in processing and retaining nutrients has been overlooked and understudied. Empirical measurements of nutrient uptake in large rivers are lacking, despite a substantial body of knowledge on nutrient transport and removal in smaller streams. Researchers...
Article
We evaluated the effects of periphyton elemental composition on the rate and ratios of N and P excretions by heptageniid mayfly larvae (Ephemeroptera). We predicted that excretion N:P ratios would relate primarily to mismatches between periphyton N:P and mayfly N:P. We immersed periphyton grown in a stream above (inlet: high N) and below (outlet: l...
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The New Zealand mud snail (NZMS) Potamopyrgus antipodarum is rapidly invading North American freshwaters, leading to speculation that native fisheries, especially those involving trout, will be negatively impacted. To assess whether trout would consume NZMSs and could assimilate nutrients from them, we conducted a laboratory N tracer study, a labor...
Article
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We evaluate the current state of knowledge concerning the ecosystem- and community-level importance of N2 fixation in streams. We reviewed the literature reporting N2-fixation contributions to stream N budgets and compared in-stream N2-fixation rates to denitrification and dissolved inorganic N (DIN)-uptake rates. In-stream N2 fixation rarely contr...
Article
Full-text available
We used whole-stream steady-state 15N-labeled nitrate (15NO3-) and conservative tracer (Cl-) additions to investigate the hydraulic and physiochemical factors controlling denitrification in the hyporheic zone (HZ) of an upland agricultural stream. We measured solute concentrations (15NO3-, 15N2(g), as well as NO3-, DOC, DO, Cl-), and hydraulic tran...
Article
Full-text available
In many watersheds, lakes and streams are hydrologically linked in spatial patterns that influence material transport and retention. We hypothesized that lakes affect stream nutrient cycling via modifications to stream hydrogeomorphology, source-waters, and biological communities. We tested this hypothesis in a lake district of the Sawtooth Mountai...
Article
The location of a stream reach relative to other landforms in a watershed is an important attribute. We hypothesized that lakes disrupt the frequency of finer, more mobile sediments and thereby change sediment transport processes such that benthic substrates are more stable (i.e., less mobile) below lakes than above lakes. In turn, we hypothesized...
Article
Lakes are common in glaciated mountain regions and geomorphic principles suggest that lake modifications to water and sediment fluxes should affect downstream channels. Lakes in the Sawtooth Mountains, Idaho, USA, were created during glaciation and we sought to understand how and to what extent glacial morphology and lake disruption of fluxes contr...
Article
The hydrology of streams and lakes has been well studied as separate ecosystems; however, the behavior and implications of hydrologic linkages between these ecosystems have been little considered. We analyzed the surface-water hydrodynamics of a stream–lake ecosystem for 3 years in the Sawtooth Mountains, Idaho, USA to understand how this coupled a...
Article
Relatively little is known about soil organic carbon (SOC) dynamics in montane ecosystems of the semi-arid western U.S. or the stability of current SOC pools under future climate change scenarios. We measured the distribution and quality of SOC in a mosaic of rangeland-forest vegetation types that occurs under similar climatic conditions on non-cal...
Article
Transient storage is often represented as characterizing the hyporheic zone, but it may also represent storage in the channel. We attempted to separate the size and exchange rate of both storage types using a combination of rhodamine WT tracer injections and cross-sectional flow velocity measurements, coupled with inverse modeling using STAMMT-L (a...
Article
Stream form and hydrologic processes may indirectly drive nutrient uptake, however developing predictive relationships has been elusive. Problems in establishing such relationships may lie in the sets of streams analyzed, which often span diverse channel-sizes, geology, and regions, or are too geomorphically similar. We collected field data on stre...
Article
Watershed structure can have a profound effect on physical, chemical, and biological characteristics of streams. We investigated stream reaches above and below lakes in three watersheds that varied in the size and numbers of lakes in the Sawtooth Mountains to address how lakes affect sediment mobility and how this in turn affects algal biomass. Dur...
Article
We have initiated an investigation to understand the factors controlling nitrate (NO3-) retention and denitrification in hyporheic zones of small streams and to quantify the fraction of nitrate retention in these streams due to hyporheic exchange. We are testing three hypotheses: (1) hyporheic denitrification in headwater, forested streams will be...
Article
Flood pulse inundation of riparian forests alters rates of nutrient retention and organic matter processing in the aquatic ecosystems formed in the forest interior. Along the Middle Rio Grande (New Mexico, USA), impoundment and levee construction have created riparian forests that differ in their inter-flood intervals (IFIs) because some floodplain...
Article
Summary1. Groundwater nitrate contamination has become a worldwide problem as increasing amounts of nitrogen fertilisers are used in agriculture. Alluvial groundwater is uniquely juxtaposed between soils and streams. Hydrological connections among these subsystems regulate nutrient cycling.2. We measured denitrification using an in situ acetylene-b...
Article
In mountain landscapes, stream form changes rapidly downstream, though this continuum is modified by local controls such as valley confinement, knickpoints, and lakes. Streams flowing into and out-of lakes may have different geomorphic characteristics than watershed position would predict because lakes attenuate flows and trap transported sediment....
Article
We present experimental evidence of the potential biodegradability of five dissolved free monosaccharides and disaccharides in three different subsystems of the Garonne River: the surface water, the hyporheic zone and the riparian groundwater. A first experiment of incubation of these sugars, alone and in combination, was conducted in surface water...
Article
Full-text available
In groundwater ecosystems, in situ primary production is low, and metabolism depends on organic matter inputs from other regions of the catchment. Heterotrophic metabolism and biogeochemistry in the floodplain groundwater of a headwater catchment (Rio Calaveras, New Mexico, USA) were examined to address the following questions: (1) How do groundwat...