Todd V. Royer's research while affiliated with Indiana University East and other places

Publications (108)

Article
Full-text available
Agriculture alters the biogeochemical cycling of nutrients such as nitrogen (N), phosphorus (P), and silicon (Si) which contributes to the stoichiometric imbalance among these nutrients in aquatic systems. Limitation of Si relative to N and P can facilitate the growth of non-siliceous, potentially harmful, algal taxa which has severe environmental...
Article
Full-text available
A unified conceptual framework for river corridors requires synthesis of diverse site‐, method‐ and discipline‐specific findings. The river research community has developed a substantial body of observations and process‐specific interpretations, but we are still lacking a comprehensive model to distill this knowledge into fundamental transferable c...
Article
Full-text available
Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low‐nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing clima...
Article
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Agriculturally-driven land use change and hydrologic modifications have influenced solute transport in midwestern U.S. streams. A clear understanding of the mechanisms driving nutrient export from agricultural watersheds will be critical in mitigating diffuse nutrient pollution, given anticipated shifts in hydrology associated with a changing clima...
Preprint
Full-text available
Agriculture alters the biogeochemical cycling of nutrients such as nitrogen (N), phosphorus (P), and silicon (Si) which contributes to the stoichiometric imbalance among these nutrients in aquatic systems. Limitation of Si relative to N and P can facilitate the growth of non-siliceous, potentially harmful, algal taxa which has severe environmental...
Article
Environmental impacts on freshwater ecosystems persist due to inputs of excess fertilizer to agricultural landscapes. Conservation efforts, such as cover crops, are being encouraged to reduce nitrogen (N) and phosphorus (P) runoff from fields, but their effects on working lands are rarely documented. We quantified reductions of nitrate-N and solubl...
Article
Excess phosphorus (P) from agriculture is a leading cause of harmful and nuisance algal blooms in many freshwater ecosystems. Throughout much of the midwestern United States, extensive networks of subsurface tile drains remove excess water from fields and allow for productive agriculture. This enhanced drainage also facilitates the transport of P,...
Preprint
A unified conceptual framework for river corridors requires synthesis of diverse site-, method- and discipline-specific findings. The river research community has developed a substantial body of observations and process-specific interpretations, but we are still lacking a comprehensive model to distill this knowledge into fundamental transferable c...
Article
A significant fraction of Earth's land surface is used for agriculture, which has led to extensive modification and degradation of streams and rivers. Although highly modified, agricultural streams offer important opportunities for advancing our understanding of agroecosystems and applying the principles of translational ecology. Using examples fro...
Article
The Midwestern US is a highly productive agricultural region, and extended crop‐free periods in winter/spring can result in nitrogen (N) and phosphorus (P) losses to waterways that degrade downstream water quality. Planting winter cover crops can improve soil health while reducing nutrient leaching from farm fields during the fallow period. In this...
Article
Subsurface tile drainage speeds water removal from agricultural fields that are historically prone to flooding. While managed drainage systems improve crop yields, they can also contribute to the eutrophication of downstream ecosystems, as tile‐drained systems are conduits for nutrients to adjacent waterways. The changing climate of the Midwestern...
Article
Floodplain restoration constructed via the two-stage ditch in agricultural streams has the potential to enhance nutrient retention and prevent the eutrophication of downstream ecosystems. Identifying the role of biotic and abiotic factors influencing soluble reactive phosphorus (SRP) retention in floodplains is of interest given that changing redox...
Article
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Although most field and modeling studies of river corridor exchange have been conducted at scales ranging from tens to hundreds of meters, results of these studies are used to predict their ecological and hydrological influences at the scale of river networks. Further complicating prediction, exchanges are expected to vary with hydrologic forcing a...
Article
Full-text available
A comprehensive set of measurements and calculated metrics describing physical, chemical, and biological conditions in the river corridor is presented. These data were collected in a catchment-wide, synoptic campaign in the H. J. Andrews Experimental Forest (Cascade Mountains, Oregon, USA) in summer 2016 during low-discharge conditions. Extensive c...
Article
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The transport and processing of nutrients and organic matter in streams are important functions that influence the condition of watersheds and downstream ecosystems. In this study, we investigated the effects of streambed sediment removal on biogeochemical cycling in Fawn River, a gravel-bottomed river in Indiana, U.S.A. We measured stream metaboli...
Article
Full-text available
Ratios of nitrogen (N), phosphorus (P), and dissolved silica (DSi) influence how algal communities respond to nutrient loading, and DSi limitation can facilitate cyanobacterial dominance. The indicator of coastal eutrophication potential (ICEP), described previously by other researchers, predicts production by diatoms vs. nonsiliceous taxa based on...
Article
This study seeks to improve understanding of temperature patterns in reservoir outflows. We examined water temperatures in an irrigation storage reservoir, Island Park Reservoir, and its outflow, Henry’s Fork of the Snake River in eastern Idaho. Our objectives were to (1) quantify the extent to which daily temperature ranges in the reservoir outflo...
Article
Full-text available
A comprehensive set of measurements and calculated metrics describing physical, chemical, and biological conditions in the river corridor is presented. These data were collected in a catchment-wide, synoptic campaign in Lookout Creek within the H.J. Andrews Experimental Forest (Cascade Mountains, Oregon, USA) in summer 2016 during low discharge con...
Article
Full-text available
Although most field and modeling studies of river corridor exchange have been conducted a scales ranging from 10’s to 100’s of meters; results of these studies are used to predict their ecological and hydrological influences at the scale of river networks. Further complicating prediction, exchange are expected to vary with hydrologic forcing and th...
Article
Full-text available
Plain Language Summary Runoff of excess nutrients from crop fertilizers applied throughout the Mississippi‐Atchafalaya River Basin, particularly nitrogen (N) and phosphorus (P), pollute freshwater and coastal ecosystems such as the Gulf of Mexico. Though agriculture is the main source, year‐to‐year variation in the size of nutrient loads is largely...
Article
Full-text available
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to...
Article
Full-text available
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to...
Article
Full-text available
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to...
Article
Full-text available
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to...
Article
Agricultural land use in the Midwestern U.S. is the major source of nitrogen (N) causing recurring hypoxia in the northern Gulf of Mexico. Despite efforts to reduce losses, N export from tile-drained, agricultural watersheds throughout the Corn Belt persists. The use of effective agricultural conservation practices can reduce N loss from fields, ye...
Article
Expansion and intensification of managed landscapes for agriculture have resulted in severe unintended global impacts, including degradation of arable land and eutrophication of receiving water bodies. Modern agricultural practices rely on significant direct and indirect human energy inputs through farm machinery and chemical use, respectively, whi...
Article
Hyporheic restoration is of increasing interest given the role of hyporheic zones in supporting ecosystem services and functions. Given the prevalence of sediment pollution to waterways, an emerging restoration technique involves the removal of sediment from the intersticies of gravel‐bed streams. Here, we document streambed sediment removal follow...
Article
The insecticidal Cry1Ab protein expressed by transgenic (Bt) maize can enter adjacent water bodies via multiple pathways, but its fate in stream ecosystems is not as well studied as in terrestrial systems. In this study, we used a combination of field sampling and laboratory experiments to examine the occurrence, leaching, and degradation of solubl...
Conference Paper
Accurately estimating watershed nutrient export can be challenging as traditional monitoring approaches using grab samples often underestimate nutrient loads during storms. Continuous nitrate-N sensors offer an opportunity to examine nutrient dynamics on a more resolved temporal scale that could help document benefits of conservation and restoratio...
Conference Paper
Traditional monitoring approaches using grab samples can present limitations to accurately estimating watershed nutrient export during storms. Continuous nitrate-N sensors offer an opportunity to examine nutrient dynamics on a more resolved temporal scale that could help document benefits of conservation and restoration. We deployed continuous nitr...
Article
Full-text available
Background The nitrogen (N) cycle consists of complex microbe-mediated transformations driven by a variety of factors, including diversity and concentrations of N compounds. In this study, we examined taxonomic diversity and N substrate utilization by heterotrophic bacteria isolated from streams under complex and simple N-enrichment conditions. Res...
Article
Western Lake Erie Basin (WLEB) is the most intensively farmed region of the Great Lakes. Because of the flat topography and poorly-drained soils many farmers rely on drainage management practices (e.g., subsurface tile drainage, ditch channelization) to maintain productive agriculture. However, these practices also facilitate the delivery of excess...
Article
Traditional sampling methods for dissolved organic matter (DOM) in streams limit opportunities for long-term studies due to time and cost constraints. Passive DOM samplers were constructed following a design proposed previously which utilizes diethylaminoethyl (DEAE) cellulose as a sampling medium, and they were deployed throughout a temperate stre...
Article
Agricultural activities have heavily altered the nitrogen (N) cycle in stream ecosystems draining croplands, particularly in the midwestern United States. However, our knowledge about dissolved organic N (DON) biogeochemistry in agricultural ecosystems is limited. From January 2011 to June 2012, we investigated DON dynamics in an agricultural headw...
Article
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Denitrifiers remove fixed nitrogen from aquatic environments and hydrologic conditions are one potential driver of denitrification rate and denitrifier community composition. In this study, two agriculturally impacted streams in the Sugar Creek watershed in Indiana, USA with different hydrologic regimes were examined; one stream is seasonally ephem...
Article
We present a comprehensive data set of gross primary production (GPP) and ecosystem respiration (ER) in open-canopy, nutrient-rich streams draining row-crop agriculture in the midwestern United States. We used two approaches to characterize temporal and spatial variation in whole-stream metabolism: continuous measurements in one agricultural stream...
Article
To investigate the coupling between carbon (C) and phosphorus (P) cycling in a human-altered stream, we conducted a whole-ecosystem manipulation of the labile dissolved organic carbon (DOC) pool in a nitrate (NO3-)-rich stream in the midwestern United States. For 6 d, we increased stream DOC by similar to 1 mg L-1 through a continuous addition of s...
Article
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Pharmaceutical and personal care products are ubiquitous in surface waters but their effects on aquatic biofilms and associated ecosystem properties are not well understood. We measured in situ responses of stream biofilms to six common pharmaceutical compounds (caffeine, cimetidine, ciprofloxacin, diphenhydramine, metformin, ranitidine, and a mixt...
Article
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In streams, benthic bacterial communities are integral to multiple aspects of ecosystem function, including carbon and nitrogen cycles. Variation both in terms of bacterial community structure (based on taxo-nomic and/or functional genes) and function can reveal potential drivers of spatiotemporal patterns in stream pro-cesses. In this study, the a...
Article
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Carbon (C) and nitrogen (N) are strongly coupled across ecosystems due to stoichiometrically bal-anced assimilatory demand as well as dissimilatory processes such as denitrification. Microorganisms mediate these biogeochemical cycles, but how microbial communities respond to environmental changes, such as dissolved organic carbon (DOC) availability...
Article
The number of anthropogenic compounds that occur in aquatic ecosystems today is in the thousands, many at trace concentrations. One group of compounds that has captured the interest of both the scientific community and the general public is pharmaceutical and personal care products (PPCPs), for example, hormones, chemotherapy drugs, antihistamines,...
Article
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Anthropogenic activities increase rates of N input to the environment, and loss of this N is controlled by several factors, including denitrification. Streams are the initial receptors of terrestrial N, but the extent to which variability in stream denitrification rates are related to differences in microbial community structure are largely unexplo...
Article
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Inland freshwaters transform and retain up to half of the carbon that enters from the terrestrial environment and have recently been recognized as important components of regional and global carbon budgets. However, the importance of small streams to these carbon budgets is not well understood due to the lack of globally-distributed data, especiall...
Article
Processing of leaf litter is an important function in many environments and is influenced strongly by microorganisms. We investigated interactions between an aquatic hyphomycete, Tetrachaetum elegans, and two bacteria from the Cytophaga-Flavobacterium-Bacteroides group, that were isolated from decaying leaves in a stream. Laboratory experiments wer...
Conference Paper
Background/Question/Methods Land which has been subject to intense agricultural activity can play a key role in determining the health of aquatic ecosystems. Fertilizer runoff can lead to extremely high concentrations of nitrogen in streams, thus altering these aquatic resources. However, the microbial process of denitrification can remove nitrog...
Conference Paper
Background/Question/Methods Understanding the nitrogen cycle in streams is essential because anthropogenic inputs have dramatically increased nitrogen loading. Downstream transport of these nutrients can result in undesirable algal blooms and creation of “dead zones” in water bodies receiving lotic inputs. Although freshwater ecosystems harbor a...
Conference Paper
Background/Question/Methods Dissolved organic carbon (DOC) is the major source of fixed carbon in aquatic ecosystems and bacteria play a central role in its uptake in streams. DOC is also required for denitrification, a major pathway for returning nitrogen to the atmosphere. DOC in the environment is diverse, ranging from simple amino acids and m...
Article
We evaluated the effects of disturbance on stream benthic macroinvertebrates at the ecological scales of time, stream size, and burn extent in six segments of Cache Creek over the first 10 postfire years. Postfire changes in macroinvertebrate taxa richness, density, and dominant taxa in the burn streams were significantly different from those in th...
Article
Full-text available
In the midwestern United States, maize detritus enters streams draining agricultural land. Genetically modified Bt maize is commonly planted along streams and can possibly affect benthic macroinvertebrates, specifically members of the order Trichoptera, which are closely related to target species of some Bt toxins and are important detritivores in...
Article
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Widespread planting of maize throughout the agricultural Midwest may result in detritus entering adjacent stream ecosystems, and 63% of the 2009 US maize crop was genetically modified to express insecticidal Cry proteins derived from Bacillus thuringiensis. Six months after harvest, we conducted a synoptic survey of 217 stream sites in Indiana to d...
Conference Paper
Background/Question/Methods Agricultural fertilizer use has significantly increased export of bioavailable nitrogen to streams and ultimately coastal ecosystems, where eutrophication, harmful algal blooms, and hypoxia may result. Denitrification, the microbially-mediated anaerobic reduction of nitrate to dinitrogen gas, is an important N-cycle pat...
Conference Paper
Background/Question/Methods Land use is a key factor determining conditions in streams. In particular, streams impacted by surrounding agriculture receive increased nutrient loads as excess fertilizers drain from the agricultural land. Consequently, concentrations of nutrients, such as nitrogen, may be significantly higher in these streams than in...
Article
Contemporary information on road salt runoff is needed for management of water resources in regions experiencing urbanization and increased road density. We investigated seasonal Cl(-) concentrations among five streams in south-central Indiana that drained watersheds varying in degree of urbanization and ranging in size from 9.3 to 27 km(2). We als...
Article
Dissolved organic carbon (DOC) in streams draining hydrologically modified and intensively farmed watersheds has not been well examined, despite the importance of these watersheds to water quality issues and the potential of agricultural soils to sequester carbon. We investigated the dynamics of DOC for 14months during 2006 and 2007 in 6 headwater...
Article
Full-text available
Simple nitrogen (N) input/output balance calculations in agricultural systems are used to evaluate performance of nutrient management; however, they generally rely on extensive assumptions that do not consider leaching, denitrification, or annual depletion of soil N. We constructed a relatively complete N mass balance for the Big Ditch watershed, a...
Article
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Sediments can be important in regulating stream water P concentrations, and this has implications for establishing nutrient standards that have not been fully investigated. We evaluated abiotic and biotic processes to better understand the role of sediments in determining stream water dissolved P concentrations. Sediment and stream water samples we...
Article
Headwater streams draining agricultural landscapes receive maize leaves (Zea mays L.) via wind and surface runoff, yet the contribution of maize detritus to organic-matter processing in agricultural streams is largely unknown. We quantified decomposition and microbial respiration rates on conventional (non-Bt) and genetically engineered (Bt) maize...
Article
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Decomposition of leaf litter is a microbial mediated process that helps to transfer energy and nutrients from leaves to higher trophic levels in woodland streams. Generally, aquatic hyphomycetes are viewed as the major fungal group responsible for leaf litter decomposition. In this study, traditional microscopic examination (based on identification...
Article
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Nutrient enrichment is a frequently cited cause for biotic impairment of streams and rivers in the USA. Efforts are underway to develop nutrient standards in many states, but defensible nutrient standards require an empirical relationship between nitrogen (N) or phosphorus (P) concentrations and some criterion that relates nutrient levels to the at...
Article
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The influence of specific stressors, such as nutrient enrichment and physical habitat degradation, on biotic integrity requires further attention in Midwestern streams. We sampled 53 streams throughout Illinois and examined relationships between macroinvertebrate community structure and numerous physicochemical parameters. Streams were clustered in...
Article
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Corn (Zea mays L.) that has been genetically engineered to produce the Cry1Ab protein (Bt corn) is resistant to lepidopteran pests. Bt corn is widely planted in the midwestern United States, often adjacent to headwater streams. We show that corn byproducts, such as pollen and detritus, enter headwater streams and are subject to storage, consumption...
Article
1. Anthropogenic activities have increased reactive nitrogen availability, and now many streams carry large nitrate loads to coastal ecosystems. Denitrification is potentially an important nitrogen sink, but few studies have investigated the influence of benthic organic carbon on denitrification in nitrate-rich streams. 2. Using the acetylene-block...
Article
Agriculture is a major nonpoint source of phosphorus (P) in the Midwest, but how surface runoff and tile drainage interact to affect temporal concentrations and fluxes of both dissolved and particulate P remains unclear. Our objective was to determine the dominant form of P in streams (dissolved or particulate) and identify the mode of transport of...
Article
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Although fungi, bacteria, and specific bacterial taxa, such as the actinomycetes, have been studied extensively in various habitats, few studies have examined them simultaneously, especially on decomposing leaves in streams. In this study, sugar maple and white oak leaves were incubated in a stream in northeastern Ohio for 181 days during which sam...