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Shifts in plant community structure in shrub and grass-dominated ecosystems are occurring over large land areas in the western US. It is not clear what effect this vegetative change will have on rates of carbon and nitrogen cycling, and thus long-term ecosystem productivity. To study the effect of different plant species on the decomposability of soil organic substrates and rates of C- and N-cycling, we conducted laboratory incubations of soils from a 15-yr-old experimental plot where big sagebrush (Artemisia tridentata Nutt.) and crested wheatgrass (Agropyron desertorum [Fisch.] Schult.) plants had been planted in a grid pattern. Soil samples collected from beneath crested wheatgrass had significantly greater total...
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The Maumee River transports huge loads of nitrogen (N) and phosphorus (P) to Lake Erie. The increased concentrations of N and P are causing eutrophication of the lake, creating hypoxic zones, and contributing to phytoplankton blooms. It is hypothesized that the P loads are a major contributor to harmful algal blooms that occur in the western basin of Lake Erie, particularly in summer. The Maumee River has been identified by the United States Environmental Protection Agency as a priority watershed where action needs to be taken to reduce nutrient loads. This study quantified rates of biogeochemical processes affecting downstream flux of N and P by 1) measuring indices of potential sediment P retention and 2) measuring...
Nitric oxide (NO) is a relatively short-lived trace gas that reacts with oxygen in the troposphere to produce the air pollutant ozone. It also reacts with water vapor to form nitric and nitrous acids, which acidify precipitation and increase N deposition. Models currently used to predict soil NO fluxes are based on the assumption that NO flux is proportional to the gross rate of nitrification or N mineralization; however, this assumption has not been tested because of the difficulty in measuring gross N-cycling rates in situ. We measured soil NO fluxes, gross and net N-cycling rates, and a variety of other soil characteristics in the forest floor and intact soil cores at nine undisturbed forest and rangeland ecosystems...
Coupled measurements of nitrate (NO3 −), nitrogen (N), and oxygen (O) isotopic composition (δ 15NNO3 and δ 18ONO3) were made in surface waters of Monterey Bay to investigate multiple N cycling processes occurring within surface waters. Profiles collected throughout the year at three sites exhibit a wide range of values, suggesting simultaneous and variable influence of both phytoplankton NO3 − assimilation and nitrification within the euphotic zone. Specifically, increases in δ 18ONO3 were consistently greater than those in δ 15NNO3. A coupled isotope steady state box model was used to estimate the amount of NO3 − supplied by nitrification in surface waters relative to that supplied from deeper water. The model...
Soils that are physically disturbed are often reported to show net nitrification and NO3? loss. To investigate the response of soil N cycling rates to soil mixing, we assayed gross rates of mineralization, nitrification, NH4+ consumption, and NO3? consumption in a suite of soils from eleven woody plant communities in Oregon, New Mexico, and Utah. Results suggest that the common response of net NO3? flux from disturbed soils is not a straightforward response of increased gross nitrification, but instead may be due to the balance of several factors. While mineralization and NH4+ assimilation were higher in mixed than intact cores, NO3? consumption declined. Mean net nitrification was 0.12 mg N kg?1 d?1 in disturbed...
Nitrate (NO3 −) concentrations and dual isotopic composition (δ 15N and δ 18O) were measured during various seasons and tidal conditions in Elkhorn Slough to evaluate mixing of sources of NO3 − within this California estuary. We found the isotopic composition of NO3 − was influenced most heavily by mixing of two primary sources with unique isotopic signatures, a marine (Monterey Bay) and terrestrial agricultural runoff source (Old Salinas River). However, our attempt to use a simple two end-member mixing model to calculate the relative contribution of these two NO3 − sources to the Slough was complicated by periods of nonconservative behavior and/or the presence of additional sources, particularly during the dry...
Groundwater nitrification is a poorly characterized process affecting the speciation and transport of nitrogen. Cores from two sites in a plume of contamination were examined using culture-based and molecular techniques targeting nitrification processes. The first site, located beneath a sewage effluent infiltration bed, received treated effluent containing O2 (> 300 µM) and NH4+ (51–800 µM). The second site was 2.5 km down-gradient near the leading edge of the ammonium zone within the contaminant plume and featured vertical gradients of O2, NH4+, and NO3− (0–300, 0–500, and 100–200 µM with depth, respectively). Ammonia- and nitrite-oxidizers enumerated by the culture-based MPN method were low in abundance at both...
Anthropogenic activity is causing dramatic changes in the nitrogen (N) cycle in many ecosystems. Most research has focused on the increase in N input caused by atmospheric deposition and invasion of N-fixing species, and on their effects on resource availability and species composition. However, in contrast to many ecosystems experiencing large increases in N input, many arid ecosystems are experiencing loss of nutrients due to land-use change. An important component of many arid ecosystems on a worldwide basis is the microbiotic crust, a biological soil crust composed of lichens, cyanobacteria, mosses, and algae. Nitrogen fixation by lichens and cyanobacteria comprising the crust is the primary source of N input...
This dataset includes data collected to determine the effects of formaldehyde on nitrification processes in biofilters of recirculating aquaculture systems (RAS) from two field trials. Biofilter nitrification was monitored by measuring the levels of total ammonia nitrogen, nitrite, and nitrate in experimental aquaria containing a small biofilter before and after formaldehyde was applied to the test system.
The soil emission rates (fluxes) of nitrous oxide (N2O) and nitrogen oxides (NO + NO2 = NOx) through a seasonal snowpack were determined by a flux gradient method from near-continuous 2-year measurements using an automated system for sampling interstitial air at various heights within the snowpack from a subalpine site at Niwot Ridge, Colorado. The winter seasonal-averaged N2O fluxes of 0.047-0.069 nmol m-2 s-1 were ~15 times higher than observed NOx fluxes of 0.0030-0.0067 nmol m-2 s-1. During spring N2O emissions first peaked and then dropped sharply as the soil water content increased from the release of snowpack meltwater, while other gases, including NOx and CO2 did not show this behavior. To compare and contrast...
Shifts in plant community structure in shrub and grass-dominated ecosystems are occurring over large land areas in the western US. It is not clear what effect this vegetative change will have on rates of carbon and nitrogen cycling, and thus long-term ecosystem productivity. To study the effect of different plant species on the decomposability of soil organic substrates and rates of C- and N-cycling, we conducted laboratory incubations of soils from a 15-yr-old experimental plot where big sagebrush (Artemisia tridentata Nutt.) and crested wheatgrass (Agropyron desertorum [Fisch.] Schult.) plants had been planted in a grid pattern. Soil samples collected from beneath crested wheatgrass had significantly greater total...
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The Maumee River transports huge loads of nitrogen (N) and phosphorus (P) to Lake Erie. The increased concentrations of N and P are causing eutrophication of the lake, creating hypoxic zones, and contributing to phytoplankton blooms. It is hypothesized that the P loads are a major contributor to harmful algal blooms that occur in the western basin of Lake Erie, particularly in summer. The Maumee River has been identified by the United States Environmental Protection Agency as a priority watershed where action needs to be taken to reduce nutrient loads. This study quantified rates of biogeochemical processes affecting downstream flux of N and P by 1) measuring indices of potential sediment P retention and 2) measuring...
This dataset includes laboratory data collected to determine the effects of hydrogen peroxide on nitrification processes in biofilters of recirculating aquaculture systems (RAS). Data from the laboratory studies were used to inform methods used to conduct field trials in pilot- and commercial-scale RAS. Biofilter nitrification was monitored by measuring the levels of total ammonia-nitrogen, nitrite-nitrogen, and nitrate-nitrogen in experimental aquaria containing a small biofilter before and after hydrogen peroxide was applied to the test system. There are 4 excel workbooks associated with this data set: RASHP Range finding Trial.csv, RASHP Definitive Trial.csv, Hydrogen Peroxide Lab Studies.csv, and DO after HP...
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Lake Superior is historically a nutrient poor lake that does not typically support significant cyanobacterial blooms. However, the lake has been experiencing an increase in blooms in the western portion of the basin recently. The largest blooms documented have occurred after recent major flooding events, indicating that nutrients transported to the lake during these events may be a source for the blooms. This study looks into the combination of streambed sediment-derived nutrient data during base flow conditions and suspended and settled sediment-derived nutrient data from storm events to provide information about nutrient transformation and storage in the river networks of the Bois Brule River and Siskiwit River...
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Data describe the results of a controlled laboratory mesocosm experiment evaluating the influence of a nitrifier enriched microbial community on silver carp (Hypophthalmichthys molitrix) milt eDNA degradation. Parameters described include the concentration results, limit of detection, and limit of quantification of two silver carp specific quantitative PCR assays and water chemistry results of experimental mesocosms.
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Synopsis: This study summarized results of a comparative 15N-tracer study from a wide variety of sites throughout the United States, to derive general principles related to headwater streams and nitrogen dynamics. Standardized protocols were applied in 12 headwater streams representing a wide diversity of biomes throughout the United States. These sites were part of the Lotic Intersite Nitrogen eXperiment (LINX). The most rapid uptake and transformation of inorganic nitrogen occurred in the smallest streams. Ammonium entering these streams was removed within a few tens to hundreds of meters, primarily through assimilation by microorganisms, sorption to sediments, and nitrification. Nitrate was also removed from...
This dataset includes laboratory data collected to determine the effects of formaldehyde on nitrification processes in biofilters of recirculating aquaculture systems (RAS). Data from the laboratory studies were used to inform methods used to conduct field trials in a pilot and commercial-scale RAS. Biofilter nitrification was monitored by measuring the levels of total ammonia nitrogen, nitrite, and nitrate in experimental aquaria containing a small biofilter before and after formaldehyde was applied to the test system.
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The Maumee River transports huge loads of nitrogen (N) and phosphorus (P) to Lake Erie. The increased concentrations of N and P are causing eutrophication of the lake, creating hypoxic zones, and contributing to phytoplankton blooms. It is hypothesized that the P loads are a major contributor to harmful algal blooms that occur in the western basin of Lake Erie, particularly in summer. The Maumee River has been identified by the United States Environmental Protection Agency as a priority watershed where action needs to be taken to reduce nutrient loads. This study quantified rates of biogeochemical processes affecting downstream flux of N and P by 1) measuring indices of potential sediment P retention and 2) measuring...
Elaeagnus angustifolia L., a nonnative N2-fixer, has established within riparian corridors of the interior western United States and is now the fourth most frequently occurring woody riparian plant in this region. We examined whether E. angustifolia alters pools and fluxes of soil inorganic N at eight sites dominated by Populus deltoides ssp. wislizeni along the Rio Grande in New Mexico over 2 years. E. angustifolia contributed a small fraction of total leaf fall (<5% across sites) but accounted for a disproportionately high amount of N (19%) that entered the system from P. deltoides and E. angustifolia leaf fall, due to the high N content (>2%) of E. angustifolia senesced leaves. Soil inorganic N concentrations...
Anthropogenic activity is causing dramatic changes in the nitrogen (N) cycle in many ecosystems. Most research has focused on the increase in N input caused by atmospheric deposition and invasion of N-fixing species, and on their effects on resource availability and species composition. However, in contrast to many ecosystems experiencing large increases in N input, many arid ecosystems are experiencing loss of nutrients due to land-use change. An important component of many arid ecosystems on a worldwide basis is the microbiotic crust, a biological soil crust composed of lichens, cyanobacteria, mosses, and algae. Nitrogen fixation by lichens and cyanobacteria comprising the crust is the primary source of N input...


map background search result map search result map Control of Nitrogen Export from Watersheds by Headwater Streams Great Lakes Restoration Initiative: Nutrient cycling in riverbed sediment in the Maumee River Basin, 2019 and 2021 Data (ver. 2.0, March 2024) Great Lakes Restoration Initiative: Nutrient cycling in riverbed sediment in the Maumee River Basin, 2019 Data Great Lakes Restoration Initiative: Nutrient cycling in riverbed sediment in the Maumee River Basin, 2021 Data (ver. 2.0, March 2024) Water chemistry and molecular eDNA data observed in experimental laboratory mesocosms exposed to different nitrogen amendments in the presence or absence of a nitrifier enriched microbial community Phosphorus and nitrogen cycling in streambed and suspended sediment in Bois Brule and Siskiwit Rivers WI, 2021-2023 Data Water chemistry and molecular eDNA data observed in experimental laboratory mesocosms exposed to different nitrogen amendments in the presence or absence of a nitrifier enriched microbial community Phosphorus and nitrogen cycling in streambed and suspended sediment in Bois Brule and Siskiwit Rivers WI, 2021-2023 Data Great Lakes Restoration Initiative: Nutrient cycling in riverbed sediment in the Maumee River Basin, 2019 and 2021 Data (ver. 2.0, March 2024) Great Lakes Restoration Initiative: Nutrient cycling in riverbed sediment in the Maumee River Basin, 2019 Data Great Lakes Restoration Initiative: Nutrient cycling in riverbed sediment in the Maumee River Basin, 2021 Data (ver. 2.0, March 2024) Control of Nitrogen Export from Watersheds by Headwater Streams