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? Rhizodeposition, or the addition of C from roots to soil C pools, is expected to increase if net primary production is stimulated and some excess C is allocated below-ground. We investigated the effects of 5 yrs of elevated CO2 on below-ground C dynamics in a native, C3?C4 grassland ecosystem in Colorado, USA. ? Cylinder harvests following each growing season and monolith excavation at the end of the experiment provided data on root biomass, root C : N ratios, and root and soil ?13C values. We applied an isotopic mixing model to quantify new soil C inputs on elevated and ambient CO2 treatments. ? Root biomass increased by 23% and root C : N ratios increased by 26% after 5 yrs of elevated CO2. Species-specific...
Soil microbial organisms are central to carbon (C) and nitrogen (N) transformations in soils, yet not much is known about the stable isotope composition of these essential regulators of element cycles. We investigated the relationship between C and N availability and stable C and N isotope composition of soil microbial biomass across a three million year old semiarid substrate age gradient in northern Arizona. The δ15N of soil microbial biomass was on average 7.2‰ higher than that of soil total N for all substrate ages and 1.6‰ higher than that of extractable N, but not significantly different for the youngest and oldest sites. Microbial 15N enrichment relative to soil extractable and total N was low at the...
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We used a combination of stable isotope analysis of carbon and nitrogen values in nesting loggerhead sea turtle samples to describe the foraging area used by each turtle. Here we present the stable isotope values for United States Geological Survey (USGS) turtles sampled in the remote Dry Tortugas National Park, south Florida, and their assigned foraging area.
This dataset contains mercury concentrations and locations of wintering red-legged kittiwakes in the western subartic Pacific Ocean. These data support the following publication: Fleishman, AB, RA Orben, N Kokubun, A Will, R Paredes, JT Ackerman, A Takahashi, AS Kitaysky, and SA Shaffer. 2019. Wintering in the Western Subarctic Pacific increases mercury contamination of red-legged kittiwakes. Environmental Science and Technology, in press.
Two native desert shrubs were evaluated for their growth potential and water and nitrogen uptake patterns over a nitrate-contaminated aquifer at a former uranium ore-processing facility in northeastern Arizona. Sarcobatus vermiculatus and Atriplex canescens are obligate and facultative phreatophytes, respectively, that dominate the local desert plant community. The main questions we addressed were: (1) Are these shrubs able to use water or nitrogen from the alluvial aquifer? (2) If so, does grazing interfere with that ability of shrubs? (3) What would be the ideal strategy to take up N from the plume and prevent its expansion and recharge using shrubs? ?18O and ?D isotope signatures from water in plant stem samples...
* • Relative abundances of carbon and nitrogen isotopes in fungal sporocarps are useful in assessing mycorrhizal or saprotrophic status, and might provide insights into the evolutionary history of these traits. * • Sporocarps of known mycorrhizal or saprotrophic genera were collected at Woods Creek, OR, USA, and isotopically compared with foliage, litter, soils and wood collected from the same site. Possible trophic strategies were then isotopically assessed in archived specimens of the Pezizales of known molecular phylogeny from the western United States. * • At Woods Creek, mycorrhizal fungi were 3.5‰ ± 0.6‰ depleted in δ13C and 5.7‰ ± 0.4‰ enriched in δ15N compared with saprotrophic fungi. By...
For the first time in history a short pulse of water was intentionally released for environmental purposes in April–May 2014 into the final 160 km stretch of the Colorado River, south of the Mexican border. During this pulse the sources and turnover of dissolved nutrients (nitrate, ammonium, phosphate, silicate and carbon), particulate organic matter, along with stable isotopes of suspended particulate carbon and nitrogen, were studied. The river water, as it flowed along the dry riverbed became rapidly depleted in N-NO3(from 21 to 0.5 μmol L−1), while dissolved organic carbon of terrestrial C3plant origin became depleted in13C and thus more negative δ13CDOCvalues. At the confluence with the Hardy River, the pulsed...
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Data provided here describe geochemical correction of carbon-14 in dissolved inorganic carbon (DIC) for groundwater age dating. Datasets include major ion chemistry of groundwater samples, model parameter inputs, and final corrected carbon-14 in DIC. Geochemical correction was completed in two phases: determination of reactive phase mole transfers through an inverse geochemical model (PHREEQC; Parkhurst and Appleo, 1992) and tracking of isotopic mass transfer among phases (NetpathXL; Parkhusrtand Charlton, 2008). Parkhurst, D.L., and Appelo, C.A.J., 2013, Description of input and examples for PHREEQC version 3—A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical...
Tags: Cenozoic, Connecticut, Holocene, Idaho, Illinois, All tags...
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Data set includes water Sr:Ca, Ba:Ca, and δ18O for the Upper Mississippi River and tributaries and otolith Sr:Ca, Ba:Ca, and δ18O data from bigheaded carp collected in pools 19-21 of the Upper Mississippi River. Abstract from manuscript: Knowledge of environments used during early life history and movement patterns of Bighead Carp (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix), collectively termed bigheaded carps, in the Upper Mississippi River (UMR) would be valuable for informing control measures to limit further population expansion and impacts of these species. Lock and Dam 19 (LD19) is a high-head dam on the UMR that delineates downriver areas where bigheaded carps are well-established from upriver...
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Caddisfly-dominated microbial-carbonate mounds and avian eggshell fragments are common in a nearshore, oolite facies of the Tipton Shale Member of the Eocene Green River Formation. The fossils occur in a 9 m thick carbonate sequence exposed on the south-west flank of Essex Mountain, Sweetwater County, Wyoming. The eggshell was determined to be of avian origin by examination of the radial eggshell microstructure by scanning electron microscopy and polarized light microscopy. Common allochems in the limestone include: ooids, pisoids, oncoids, ostracods, gastropods, intraclasts, caddisfly larval/pupal cases, fish bones, avian bones and avian eggshell fragments. Carbonate mineralogy varies between 95% calcite and 95%...
Water use and carbon acquisition were examined in a northern Utah population of Juniperus osteosperma (Torr.) Little. Leaf-level carbon assimilation, which was greatest in the spring and autumn, was limited by soil water availability. Gas exchange, plant water potential and tissue hydrogen stable isotopic ratio (deltaD) data suggested that plants responded rapidly to summer rain events. Based on a leaf area index of 1.4, leaf-level water use and carbon acquisition scaled to canopy-level means of 0.59 mm day(-1) and 0.13 mol m(-2) ground surface day(-1), respectively. Patterns of soil water potential indicated that J. osteosperma dries the soil from the surface downward to a depth of about 1 m. Hydraulic redistribution...
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We investigated the effects of winter and summer drought on plants of the Colorado Plateau in western North America. This winter-cold, summer-hot desert region receives both winter and summer precipitation. Droughts were imposed for two consecutive years using rainout shelters. Here, we examine drought effects on the hydrologic interactions between plants and soil. We chose three perennial species for this study, representing different rooting patterns and responsiveness to precipitation pulses: Oryzopsis hymenoides, a perennial bunch grass with shallow roots; Gutierrezia sarothrae, a subshrub with dimorphic roots; and Ceratoides lanata, a predominantly deep-rooted woody shrub. Drought effects on plant water status...
The mobility and bioavailability of Se depend on its redox state, and reduction of Se oxyanions to less mobile, reduced species controls transport of this potentially toxic element in the environment. Stable isotope fractionation of Se is currently being developed as an indicator of Se immobilization through reduction. In this study, Se isotope fractionation resulting from reduction of Se(VI) and Se(IV) oxyanions by natural microbial consortia was measured in sediment slurry experiments under nearly natural conditions, with no substrate added. Experiments were conducted with a wide range of initial Se concentrations and with sediment and water from three locations with contrasting environmental settings. The products...
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Degassing thermal features at Yellowstone National Park include spectacular geysers, roiling hot springs, bubbling mud pots, fumaroles, frying pans, and areas of passive degassing characterized by steaming ground. Most of these features are readily identified by visible clouds of steam that are occasionally accompanied by a strong “rotten egg” odor from emissions of hydrogen sulfide gas. Gas compositions typically are greater than 90% carbon dioxide with lesser amounts of helium, hydrogen, hydrogen sulfide, methane, nitrogen and other trace components. The composition of the gas and relative amounts of gas and steam relate both to the type of feature as well as the geographic location within the park. In 2003 we...
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Examination of food webs and trophic niches provide insight into organisms’ functional ecology, yet few studies have examined the trophodynamics within submarine canyons, where the interaction of morphology and oceanography influences food deposition. Stable isotope analysis and Bayesian ellipses documented deep-sea food web structure and trophic niches in Baltimore Canyon and the adjacent open slopes in the U.S. Mid-Atlantic Region. Results revealed isotopically diverse feeding groups, comprising approximately 5 trophic levels. Regression analysis indicated that consumer isotope data are structured by site (canyon vs. slope), feeding group, and depth. Benthic feeders were enriched in 13C and 15N relative to suspension...
The growing awareness that plants might use a variety of nitrogen (N) forms, both organic and inorganic, has raised questions about the role of resource partitioning in plant communities. It has been proposed that coexisting plant species might be able to partition a limited N pool, thereby avoiding competition for resources, through the uptake of different chemical forms of N. In this study, we used in situ stable isotope labeling techniques to assess whether coexisting plant species of a temperate grassland (England, UK) display preferences for different chemical forms of N, including inorganic N and a range of amino acids of varying complexity. We also tested whether plants and soil microbes differ in their preference...
Rivermouth ecosystems are areas where tributary waters mix with lentic near-shore waters and provide habitat for many Laurentian Great Lakes fish and wildlife species. Rivermouths are the interface between terrestrial activities that influence rivers and the ecologically important nearshore. Stable isotopes of nitrogen (N) and carbon (C) in consumers were measured from a range of rivermouths systems to address two questions: 1) What is the effect of rivermouth ecosystems and land cover on the isotopic composition of N available to rivermouth consumers? 2) Are rivermouth consumers composed of lake-like or river-like C? For question 1, data suggest that strong relationships between watershed agriculture and consumer...
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The late Pleistocene was a climatically dynamic period, with abrupt shifts between cool-wet and warm-dry conditions. Increased effective precipitation supported large pluvial lakes and long-lived spring ecosystems in valleys and basins throughout the western and southwestern U.S., but the source and seasonality of the precipitation are debated. Here we present stable carbon and oxygen isotope data from tooth enamel of late Pleistocene herbivores recovered from paleowetland deposits at Tule Spring Fossil Beds National Monument in the Las Vegas Valley of southern Nevada, as well as modern herbivores from the surrounding area, to investigate whether winter or summer precipitation was responsible for driving the wet...
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Mesopelagic fishes represent an important component of the marine food web due to their global distributions, high abundances and ability to transport organic material throughout a large part of the water column. This study combined stable isotope (SIA) and gut content analyses (GCA) to characterize the trophic structure of mesopelagic fishes in the north central Gulf of Mexico. Additionally this study examined whether mesopelagic fishes utilized chemosynthetic energy from cold seeps. Specimens were collected (9-25 August 2007) over three deep (>1000 m) cold seeps at discrete depths (surface to 1503 m) over the diurnal cycle. Gut content analyses classified 31 species (5 families) of mesopelagic fishes into 5 feeding...
Understanding the behavior of engineered nanoparticles in the environment and within organisms is perhaps the biggest obstacle to the safe development of nanotechnologies. Reliable tracing is a particular issue for nanoparticles such as ZnO, because Zn is an essential element and a common pollutant thus present at elevated background concentrations. We synthesized isotopically enriched (89.6%) with a rare isotope of Zn (67Zn) ZnO nanoparticles and measured the uptake of 67Zn by L. stagnalis exposed to diatoms amended with the particles. Stable isotope technique is sufficiently sensitive to determine the uptake of Zn at an exposure equivalent to lower concentration range (<15 μg g−1). Without a tracer, detection...
map background search result map search result map Rhizodeposition stimulated by elevated CO2 in a semiarid grassland Palaeoenvironments associated with caddisfly-dominated microbial-carbonate mounds from the Tipton Shale Member of the Green River Formation: Eocene Lake Gosiute Carbon acquisition and water use in a Northern Utah Juniperus osteosperma (Utah juniper) population. Summer and winter drought in a cold desert ecosystem (Colorado Plateau) part I: effects on soil water and plant water uptake Trophic structure of mesopelagic fishes in the Gulf of Mexico revealed by gut content and stable isotope analyses Food-web dynamics and isotopic niches in deep-sea communities residing in a submarine canyon and on the adjacent open slopes Geochemical Correction of Carbon-14 in Dissolved Inorganic Carbon used for Groundwater Age Dating in the Glacial Aquifer System, Conterminous United States Chemical and isotopic data on gases and waters for thermal and non-thermal features across Yellowstone National Park, v. 2.0 Upper Mississippi River water and bigheaded carp otolith chemistry data Data release for Seasonality of precipitation in the southwestern United States during the late Pleistocene inferred from stable isotopes in herbivore tooth enamel Stable isotope values for Dry Tortugas nesting loggerheads sampled 2013-2018 Rhizodeposition stimulated by elevated CO2 in a semiarid grassland Stable isotope values for Dry Tortugas nesting loggerheads sampled 2013-2018 Food-web dynamics and isotopic niches in deep-sea communities residing in a submarine canyon and on the adjacent open slopes Upper Mississippi River water and bigheaded carp otolith chemistry data Summer and winter drought in a cold desert ecosystem (Colorado Plateau) part I: effects on soil water and plant water uptake Chemical and isotopic data on gases and waters for thermal and non-thermal features across Yellowstone National Park, v. 2.0 Data release for Seasonality of precipitation in the southwestern United States during the late Pleistocene inferred from stable isotopes in herbivore tooth enamel Palaeoenvironments associated with caddisfly-dominated microbial-carbonate mounds from the Tipton Shale Member of the Green River Formation: Eocene Lake Gosiute Trophic structure of mesopelagic fishes in the Gulf of Mexico revealed by gut content and stable isotope analyses Geochemical Correction of Carbon-14 in Dissolved Inorganic Carbon used for Groundwater Age Dating in the Glacial Aquifer System, Conterminous United States