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USGS2020

Use of upland and riparian areas by wintering bald eagles and implications for wind energy

Weather can shape movements of animals and alter their exposure to anthropogenic threats. Bald eagles ( Haliaeetus leucocephalus ) are increasingly at risk from collision with turbines used in onshore wind energy generation. In the midwestern United States, development of this energy source typically occurs in upland areas that bald eagles use only intermittently. Our objective was to determine the factors that cause wintering bald eagles to occupy riparian areas and riskier, upland areas. We tracked 20 bald eagles using telemetry in the Upper Midwest (MN, IA, MO, WI, IL, USA) during winter 2014–2015 and 2015–2016 and evaluated habitat use by eagles in response to variation in weather and time of year. Eagles used riparian areas more when wind speed and atmospheric pressure were low. Exclusive use of uplands was more frequent during weather systems with low pressure and high humidity and after long periods of cold weather. There was a non‐linear response to time of year (measured by days before migration) in the frequency of exclusive use of uplands or riparian areas. Probability of exclusive use of either landscape was generally constant within 95 days prior to migration. The probability of use of riparian areas, however, was markedly less during dates >100 days before migration. Our results suggest that eagles are most likely to be exposed to wind energy developments located in upland areas during low pressure systems, after long periods of cold weather, and several months before the onset of spring migration. This information helps to better understand the factors influencing bald eagle habitat use in winter and will be useful to managers and developers wishing to establish effective strategies to avoid, minimize, and mitigate take, and to survey for mortalities at wind energy developments.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2021

Conservation implications of spatiotemporal variation in the terrestrial ecology of Western spadefoots

Conservation of species reliant on ephemeral resources can be especially challenging in the face of a changing climate. Western spadefoots ( Spea hammondii ) are small burrowing anurans that breed in ephemeral pools, but adults spend the majority of their lives underground in adjacent terrestrial habitat. Western spadefoots are of conservation concern throughout their range because of habitat loss, but little is known about the activity patterns and ecology of their terrestrial life stage. We conducted a radio-telemetry study of adult western spadefoots at 2 sites in southern California, USA, from December 2018 to November 2019 to characterize their survival, behavior, and movements from breeding through aestivation to refine conservation and management for the species. Western spadefoot survival varied seasonally, with risk of mortality higher in the active season than during aestivation. The probability of movement between successive observations was higher during the winter and spring and when atmospheric moisture was high and soil water content at 10-cm depth was low. The amount of rain between observations had the strongest effect on the probability of movement between observations; for every 20 mm of rainfall between observations, western spadefoots were 2.4 times more likely to move. When movements occurred, movement rates were highest when both relative humidity and soil water content at 10-cm depth were high. The conditions under which western spadefoots were likely active on the surface, likely to have moved, and moved at the highest rates are conditions that reduce the risk of desiccation of surface-active spadefoots. Western spadefoot home range areas varied between study sites and were mostly <1 ha, although 1 individual's home range area was >6 ha. Western spadefoots rapidly dispersed from the breeding pools, and asymptotic distances from the breeding pool were generally reached by June. The asymptotic distance from the breeding pool varied between sites, with the 95th percentile of the posterior predictive distribution reaching 486 m at 1 site and 187 m at the other. Western spadefoots did not select most habitat components disproportionately to their availability, but at Crystal Cove State Park, they avoided most evaluated vegetation types (graminoids, forbs, and shrubs). Spatial variation was evident in most evaluated western spadefoot behaviors; context-dependent behavior suggests that site-specific management is likely necessary for western spadefoots. Furthermore, comparison with an earlier study of western spadefoots at Crystal Cove State Park indicated substantial temporal variation in western spadefoot behavior. Therefore, basing management decisions on short-term studies might fail to meet conservation objectives. Better understanding the influences of spatial context and climatic variation on western spadefoot behavior will improve conservation efforts for this species.

California↗

USGS2017

Historical patterns of acidification and increasing CO2 flux associated with Florida springs

Florida has one of the highest concentrations of springs in the world, with many discharging into rivers and predominantly into eastern Gulf of Mexico coast, and they likely influence the hydrochemistry of these adjacent waters; however, temporal and spatial trends have not been well studied. We present over 20 yr of hydrochemical, seasonally sampled data to identify temporal and spatial trends of pH, alkalinity, partial pressure of carbon dioxide (pCO 2 ), and CO 2 flux from five first-order-magnitude (springs that discharge greater than 2.83 m 3 s −1 ) coastal spring groups fed by the Floridan Aquifer System that ultimately discharge into the Gulf of Mexico. All spring groups had pCO 2 levels (averages 3174.3–6773.2 μatm) that were much higher than atmospheric levels of CO 2 and demonstrated statistically significant temporal decreases in pH and increases in CO 2 flux, pCO 2 , and alkalinity. Total carbon flux emissions increased from each of the spring groups by between 3.48 × 10 7 and 2.856 × 10 8 kg C yr −1 over the time period. By 2013 the Springs Groups in total emitted more than 1.1739 × 10 9 kg C yr −1 . Increases in alkalinity and pCO 2 varied from 90.9 to 347.6 μmol kg −1 and 1262.3 to 2666.7 μatm, respectively. Coastal data show higher CO 2 evasion than the open Gulf of Mexico, which suggests spring water influences nearshore waters. The results of this study have important implications for spring water quality, dissolution of the Florida carbonate platform, and identification of the effect and partitioning of carbon fluxes to and within coastal and marine ecosystems.

Florida↗

USGS2020

From forests to fish: Mercury in mountain lake food webs influenced by factors at multiple scales

Mountain lakes, while seemingly pristine, have been subjected to historical fish stocking practices and exposure to atmospherically deposited contaminants like mercury. Mercury bioaccumulation in these ecosystems varies widely due to strong environmental gradients, and there are complex, hierarchical factors that affect mercury transport and loading, methylmercury production, and food web biomagnification. We sought to assess how representative variables associated with watershed, lake, and food web‐scale processes—specifically, catchment tree cover, lake benthic primary production, and fish diet, respectively—are associated with mercury concentrations in mountain lake fish. Mean fish mercury concentrations varied threefold between lakes, with nearshore tree cover and fish diet accounting for the most variance in fish mercury. Tree cover was likely positively correlated to fish Hg due to its contributions to local deposition and its effect on lake biogeochemistry. Fish with benthic diets tended to have higher mercury concentrations, illustrating that food web processes are an important consideration when investigating drivers of contaminant bioaccumulation. Our results suggest that both landscape and ecological factors are determinants of fish mercury bioaccumulation, and thus variables at multiple scales should be considered when managing mountain lake food webs for mercury exposure risk.

Washington↗

USGS2023

Spatial and temporal variability in summertime dissolved carbon dioxide and methane in temperate ponds and shallow lakes

Small waterbodies have potentially high greenhouse gas emissions relative to their small footprint on the landscape, although there is high uncertainty in model estimates. Scaling their carbon dioxide (CO 2 ) and methane (CH 4 ) exchange with the atmosphere remains challenging due to an incomplete understanding and characterization of spatial and temporal variability in CO 2 and CH 4 . Here, we measured partial pressures of CO 2 ( p CO 2 ) and CH 4 ( p CH 4 ) across 30 ponds and shallow lakes during summer in temperate regions of Europe and North America. We sampled each waterbody in three locations at three times during the growing season, and tested which physical, chemical, and biological characteristics related to the means and variability of p CO 2 and p CH 4 in space and time. Summer means of p CO 2 and p CH 4 were inversely related to waterbody size and positively related to floating vegetative cover; p CO 2 was also positively related to dissolved phosphorus. Temporal variability in partial pressure in both gases weas greater than spatial variability. Although sampling on a single date was likely to misestimate mean seasonal p CO 2 by up to 26%, mean seasonal p CH 4 could be misestimated by up to 64.5%. Shallower systems displayed the most temporal variability in p CH 4 and waterbodies with more vegetation cover had lower temporal variability. Inland waters remain one of the most uncertain components of the global carbon budget; understanding spatial and temporal variability will ultimately help us to constrain our estimates and inform research priorities.

Limnology and Oceanography↗

USGS2026

Increasing artificial light at night enhances salmonid predator foraging efficiency in an urbanized lake

Artificial light at night (ALAN) poses a threat to ecosystems globally. It includes both direct and indirect light, or skyglow, which occurs when ALAN scatters in the atmosphere, extending beyond its original source. We analyzed ALAN trends in Lake Washington, WA, from 2014 to 2023 using Visible Infrared Imaging Radiometer Suite (VIIRS) nighttime light measurements, evaluated the relationship between in situ and satellite measurements, and modeled predator search volumes for a juvenile salmon predator, cutthroat trout ( Oncorhynchus clarki ), as a function of ambient light and turbidity conditions. Open water regions experienced significant increases in ALAN, while nearshore areas primarily showed no or negative trends, revealing the role of skyglow in shaping open water light environments. Using a visual foraging model for cutthroat trout, we found that juvenile salmon at the shallow southern pelagic site experienced light 28 times brighter, resulting in a 168% greater predation vulnerability than those at the northern site. In the Ship Canal, a narrow corridor for outmigrating salmon, predator search volumes were 249% higher than at the southern site. These contrasts in predation vulnerability demonstrate how local conditions influence predator–prey dynamics and provide critical insight for targeting mitigation of both nearshore and distant light sources.

Washington↗

USGS2023

Validity of the Landsat surface reflectance archive for aquatic science: Implications for cloud-based analysis

Originally developed for terrestrial science and applications, the US Geological Survey Landsat surface reflectance (SR) archive spanning ~ 40 yr of observations has been increasingly utilized in large-scale water-quality studies. These products, however, have not been rigorously validated using in situ measured reflectance. This letter quantifies and demonstrates the quality of the SR products by harnessing a sizeable global dataset ( N = 1100). We found that the Landsat 8/9 SR in the green and red bands marginally meet the targeted accuracy requirements (30%), whereas the uncertainties in the blue and coastal-aerosol bands ranged from 48% to 110%. We further observed > +25% biases in the visible bands of Landsat 5/7 SR, which can introduce an apparent downward trend when applied in time-series analyses combined with Landsat 8/9. Users must exercise caution when using this archive for trend analyses, and progress in atmospheric correction is required to foster advanced applications of the Landsat archive for aquatic science.

Limnology and Oceanography Letters↗

USGS2024

Arctic fishes reveal patterns in radiocarbon age across habitats and with recent climate change

Climate change alters the sources and age of carbon in Arctic food webs by fostering the release of older carbon from degrading permafrost. Radiocarbon ( 14 C) traces carbon sources and age, but data before rapid warming are rare and limit assessments over time. We capitalized on 14 C data collected ~ 40 years ago that used fish as natural samplers by resampling the same species today. Among resampled fish, those using freshwater food webs had the oldest 14 C ages (> 1000 yr BP), while those using marine food webs had the youngest 14 C ages (near modern). One migratory species encompassed the entire range of 14 C ages because juveniles fed in freshwater streams and adults fed in offshore marine habitats. Over ~ 40 yr, average 14 C ages of freshwater and marine feeding fish shifted closer to atmospheric values, suggesting a potential influence from “greening of the Arctic.”

Alaska↗

USGS2019

Review: Endophytic microbes and their potential applications in crop management

Endophytes are microbes (mostly bacteria and fungi) present in plants. Endophytic microbes are often functional in that they may carry nutrients from the soil into plants, modulate plant development, increase stress tolerance of plants, suppress virulence in pathogens, increase disease resistance in plants, and suppress development of competitor plant species. Endophytic microbes have been shown: 1) obtain nutrients in soils and transfer nutrients to plants in the rhizophagy cycle and other nutrient‐transfer symbioses; 2) increase plant growth and development; 3) reduce oxidative stress of hosts; 4) protect plants from disease; 5) deter feeding by herbivores; and 6) suppress growth of competitor plant species. Because of the effective functions of endophytic microbes, we suggest that endophytic microbes may significantly reduce use of agrochemicals (fertilizers, fungicides, insecticides, and herbicides) in the cultivation of crop plants. The loss of endophytic microbes from crop plants during domestication and long‐term cultivation could be remedied by transfer of endophytes from wild relatives of crops to crop species. Increasing atmospheric carbon dioxide levels could reduce the efficiency of the rhizophagy cycle due to repression of reactive oxygen used to extract nutrients from microbes in roots.

Pest Management Science↗

USGS2006

Analysis of the surface hydrology in a regional climate model

This paper discusses the surface hydrology of a multi‐year simulation of present day climate over the United States (US) conducted with a regional climate model (RegCM) nested within a general circulation model (GCM). The RegCM, which is run with a 60 km gridpoint spacing is interactively coupled with a state‐of‐the‐art surface physics package that includes full surface hydrology calculations (the Biosphere‐Atmosphere Transfer Scheme or BATS). The hydrologic budgets of ten regional drainage basins in the US are analysed. Model results are compared with available observations and with results from previous modelling experiments to evaluate the feasibility of using nested RegCM/GCM models for hydrology studies. In our experiment, the model captures the basic seasonality of the basin hydrologic budgets, although the simulated precipitation amounts are too high over the western US and too low over the eastern US. As a result, runoff, snow cover and soil water content are underestimated over the eastern US basins, while evaporation and runoff are overestimated in some of the western US basins. Topographically induced characteristics of precipitation, snow cover and runoff are well simulated over the mountainous western regions. Also well captured is the inter‐basin variation of hydrologic budgets which occurs in response to different climatic settings. The springtime snowmelt and peak runoff season generally occurs in the model earlier in the year than is observed. Although our work indicates that the coupled regional modelling system can be useful in applications to hydrological studies, results from this experiment indicate that better accuracy in the simulation of regional climatic variables and more detailed representation of some hydrologic processes would be required before the coupled modelling system could be used to provide accurate assessments of hydrologic responses to climate change.

Quarterly Journal of the Royal Meteorological Soci↗

USGS2003

Oxygen isotopes in nitrate: New reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration

Despite a rapidly growing literature on analytical methods and field applications of O isotope-ratio measurements of NO 3 − in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying δ 18 O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isotopic compositions for distribution as reference materials for O isotope-ratio measurements: USGS34 (KNO 3 ) with low δ 18 O and USGS35 (NaNO 3 ) with high δ 18 O and ‘mass-independent’ δ 17 O. The procedure used to produce USGS34 involved equilibration of HNO 3 with 18 O-depleted meteoric water. Nitric acid equilibration is proposed as a simple method for producing laboratory NO 3 − reference materials with a range of δ 18 O values and normal (mass-dependent) 18 O: 17 O: 16 O variation. Preliminary data indicate that the equilibrium O isotope-fractionation factor ( α ) between [NO 3 − ] and H 2 O decreases with increasing temperature from 1.0215 at 22°C to 1.0131 at 100°C. USGS35 was purified from the nitrate ore deposits of the Atacama Desert in Chile and has a high 17 O: 18 O ratio owing to its atmospheric origin. These new reference materials, combined with previously distributed NO 3 − isotopic reference materials IAEA-N3 (=IAEA-NO-3) and USGS32, can be used to calibrate local laboratory reference materials for determining offset values, scale factors, and mass-independent effects on N and O isotope-ratio measurements in a wide variety of environmental NO 3 − samples. Preliminary analyses yield the following results (normalized with respect to VSMOW and SLAP, with reproducibilities of ±0.2–0.3‰, 1 σ ): IAEA-N3 has δ 18 O = +25.6‰ and δ 17 O = +13.2‰; USGS32 has δ 18 O = +25.7‰; USGS34 has δ 18 O = −27.9‰ and δ 17 O = −14.8‰; and USGS35 has δ 18 O = +57.5‰ and δ 17 O = +51.5‰.

Rapid Communications in Mass Spectrometry↗

USGS2004

Using dual-bacterial denitrification to improve δ15N determinations of nitrates containing mass-independent 17O

The bacterial denitrification method for isotopic analysis of nitrate using N 2 O generated from Pseudomonas aureofaciens may overestimate δ 15 N values by as much as 1–2‰ for samples containing atmospheric nitrate because of mass-independent 17 O variations in such samples. By analyzing such samples for δ 15 N and δ 18 O using the denitrifier Pseudomonas chlororaphis , one obtains nearly correct δ 15 N values because oxygen in N 2 O generated by P. chlororaphis is primarily derived from H 2 O. The difference between the apparent δ 15 N value determined with P. aureofaciens and that determined with P. chlororaphis , assuming mass-dependent oxygen isotopic fractionation, reflects the amount of mass-independent 17 O in a nitrate sample. By interspersing nitrate isotopic reference materials having substantially different δ 18 O values with samples, one can normalize oxygen isotope ratios and determine the fractions of oxygen in N 2 O derived from the nitrate and from water with each denitrifier. This information can be used to improve δ 15 N values of nitrates having excess 17 O. The same analyses also yield estimates of the magnitude of 17 O excess in the nitrate (expressed as Δ 17 O) that may be useful in some environmental studies. The 1- σ uncertainties of δ 15 N, δ 18 O and Δ 17 O measurements are ±0.2, ±0.3 and ±5‰, respectively.

Rapid Communications in Mass Spectrometry↗

USGS2010

Novel silver tubing method for quantitative introduction of water into high temperature conversion systems for stable hydrogen and oxygen isotopic measurements

A new method to seal water in silver tubes for use in a TC/EA reduction unit using a semi-automated sealing apparatus can yield reproducibilities (1 standard deviation) of δ 2 H and &delta 18 O measurements of 1.0 ‰ and 0.06 ‰, respectively. These silver tubes containing reference waters may be preferred for calibration of H- and O-bearing materials analyzed with a TC/EA reduction unit. The new sealing apparatus employs a computer controlled stepping motor to produce silver tubes identical in length. The reproducibility of mass of water sealed in tubes (in a range of 200 to 400 µg) can be as good as 1 percent. Although silver tubes sealed with reference waters are robust and can be shaken or heated to 110 °C with no loss of integrity, they should not be frozen because the expansion during the phase transition of water to ice will break the cold seals and all water will be lost. They should be shipped in insulated containers. This new method eliminates air inclusions and isotopic fractionation of water associated with the loading of water into capsules using a syringe. The method is also more than an order of magnitude faster than preparing water samples in ordinary Ag capsules. Nevertheless, some laboratories may prefer loading water into silver capsules because expensive equipment is not needed, but they are cautioned to apply the necessary corrections for evaporation, back exchange with laboratory atmospheric moisture, and blank.

Rapid Communications in Mass Spectrometry↗

USGS2016

Stable isotope analyses of oxygen (18O:17O:16O) and chlorine (37Cl:35Cl) in perchlorate: reference materials, calibrations, methods, and interferences

Rationale Perchlorate (ClO 4 − ) is a common trace constituent of water, soils, and plants; it has both natural and synthetic sources and is subject to biodegradation. The stable isotope ratios of Cl and O provide three independent quantities for ClO 4 − source attribution and natural attenuation studies: δ 37 Cl, δ 18 O, and δ 17 O (or Δ 17 O or 17 Δ) values. Documented reference materials, calibration schemes, methods, and interferences will improve the reliability of such studies. Methods Three large batches of KClO 4 with contrasting isotopic compositions were synthesized and analyzed against VSMOW-SLAP, atmospheric O 2 , and international nitrate and chloride reference materials. Three analytical methods were tested for O isotopes: conversion of ClO 4 − to CO for continuous-flow IRMS (CO-CFIRMS), decomposition to O 2 for dual-inlet IRMS (O2-DIIRMS), and decomposition to O 2 with molecular-sieve trap (O2-DIIRMS+T). For Cl isotopes, KCl produced by thermal decomposition of KClO 4 was reprecipitated as AgCl and converted into CH 3 Cl for DIIRMS. Results KClO 4 isotopic reference materials (USGS37, USGS38, USGS39) represent a wide range of Cl and O isotopic compositions, including non-mass-dependent O isotopic variation. Isotopic fractionation and exchange can affect O isotope analyses of ClO 4 − depending on the decomposition method. Routine analyses can be adjusted for such effects by normalization, using reference materials prepared and analyzed as samples. Analytical errors caused by SO 4 2 − , NO 3 − , ReO 4 2 − , and C-bearing contaminants include isotope mixing and fractionation effects on CO and O 2 , plus direct interference from CO 2 in the mass spectrometer. The results highlight the importance of effective purification of ClO 4 − from environmental samples. Conclusions KClO 4 reference materials are available for testing methods and calibrating isotopic data for ClO 4 − and other substances with widely varying Cl or O isotopic compositions. Current ClO 4 − extraction, purification, and analysis techniques provide relative isotope-ratio measurements with uncertainties much smaller than the range of values in environmental ClO 4 − , permitting isotopic evaluation of environmental ClO 4 − sources and natural attenuation.

Rapid Communications in Mass Spectrometry↗

USGS2021

USGS44, a new high-purity calcium carbonate reference material for δ13C measurements

Rationale The stable carbon isotopic ( δ 13 C) reference material (RM) LSVEC Li 2 CO 3 has been found to be unsuitable for δ 13 C standardization work because its δ 13 C value increases with exposure to atmospheric CO 2 . A new CaCO 3 RM, USGS44, has been prepared to alleviate this situation. Methods USGS44 was prepared from 8 kg of Merck high-purity CaCO 3 . Two sets of δ 13 C values of USGS44 were determined. The first set of values was determined by online combustion, continuous-flow (CF) isotope-ratio mass spectrometry (IRMS) of NBS 19 CaCO 3 ( δ 13 C VPDB = +1.95 milliurey (mUr) exactly, where mUr = 0.001 = 1‰), and LSVEC Li 2 CO 3 ( δ 13 C VPDB = −46.6 mUr exactly), and normalized to the two-anchor δ 13 C VPDB-LSVEC isotope-delta scale. The second set of values was obtained by dual-inlet (DI)-IRMS of CO 2 evolved by reaction of H 3 PO 4 with carbonates, corrected for cross contamination, and normalized to the single-anchor δ 13 C VPDB scale. Results USGS44 is stable and isotopically homogeneous to within 0.02 mUr in 100-μg amounts. It has a δ 13 C VPDB-LSVEC value of −42.21 ± 0.05 mUr. Single-anchor δ 13 C VPDB values of −42.08 ± 0.01 and −41.99 ± 0.02 mUr were determined by DI-IRMS with corrections for cross contamination. Conclusions The new high-purity, well-homogenized calcium carbonate isotopic reference material USGS44 is stable and has a δ 13 C VPDB-LSVEC value of −42.21 ± 0.05 mUr for both EA/IRMS and DI-IRMS measurements. As a carbonate relatively depleted in 13 C, it is intended for daily use as a secondary isotopic reference material to normalize stable carbon isotope delta measurements to the δ 13 C VPDB-LSVEC scale. It is useful in quantifying drift with time, determining mass-dependent isotopic fractionation (linearity correction), and adjusting isotope-ratio-scale contraction. Due to its fine grain size (smaller than 63 μm), it is not suitable as a δ 18 O reference material. A δ 13 C VPDB-LSVEC value of −29.99 ± 0.05 mUr was determined for NBS 22 oil.

Rapid Communications in Mass Spectrometry↗

USGS2012

Perils of categorical thinking: "Oxic/anoxic" conceptual model in environmental remediation

Given ambient atmospheric oxygen concentrations of about 21 percent (by volume), the lower limit for reliable quantitation of dissolved oxygen concentrations in groundwater samples is in the range of 0.1–0.5 mg/L. Frameworks for assessing in situ redox condition are often applied using a simple two-category (oxic/anoxic) model of oxygen condition. The "oxic" category defines the environmental range in which dissolved oxygen concentrations are clearly expected to impact contaminant biodegradation, either by supporting aerobic biodegradation of electron-donor contaminants like petroleum hydrocarbons or by inhibiting anaerobic biodegradation of electron-acceptor contaminants like chloroethenes. The tendency to label the second category "anoxic" leads to an invalid assumption that oxygen is insignificant when, in fact, the dissolved oxygen concentration is less than detection but otherwise unknown. Expressing dissolved oxygen concentrations as numbers of molecules per volume, dissolved oxygen concentrations that fall below the 0.1 mg/L field detection limit range from 1 to 1017 molecules/L. In light of recent demonstrations of substantial oxygen-linked biodegradation of chloroethene contaminants at dissolved oxygen concentrations well below the 0.1–0.5 mg/L field detection limit, characterizing "less than detection" oxygen concentrations as "insignificant" is invalid.

Remediation Journal↗

USGS2015

Water-quality assessment of the Lower Grand River Basin, Missouri and Iowa, USA, in support of integrated conservation practices

The effectiveness of agricultural conservation programmes to adequately reduce nutrient exports to receiving streams and to help limit downstream hypoxia issues remains a concern. Quantifying programme success can be difficult given that short-term basin changes may be masked by long-term water-quality shifts. We evaluated nutrient export at stream sites in the 44 months that followed a period of increased, integrated conservation implementation within the Lower Grand River Basin. These short-term responses were then compared with export that occurred in the main stem and adjacent rivers in northern Missouri over a 22-year period to better contextualize any recent changes. Results indicate that short-term (October 2010 through May 2014) total nitrogen (TN) concentrations in the Grand River were 20% less than the long-term average, and total phosphorus (TP) concentrations were 23% less. Nutrient reductions in the short term were primarily the result of the less-than-average precipitation and, consequently, streamflow that was 36% below normal. Therefore, nutrient concentrations measured in tributary streams were likely less than normal during the implementation period. Northern Missouri streamflow-normalized TN concentrations remained relatively flat or declined over the period 1991 through 2013 likely because available sources of nitrogen, determined as the sum of commercial fertilizers, available animal manures and atmospheric inputs, were typically less than crop requirement for much of that time frame. Conversely, flow-normalized stream TP concentrations increased over the past 22 years in northern Missouri streams, likely in response to many years of phosphorus inputs in excess of crop requirements. Stream nutrient changes were most pronounced during periods that coincided with the major tillage, planting and growth phases of row crops and increased streamflow. Nutrient reduction strategies targeted at the period February through June would likely have the greatest impact on reducing nutrient export from the basin. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

River Research and Applications↗

USGS2017

Weather radar data correlate to hail-induced mortality in grassland birds

Small-bodied terrestrial animals such as songbirds (Order Passeriformes) are especially vulnerable to hail-induced mortality; yet, hail events are challenging to predict, and they often occur in locations where populations are not being studied. Focusing on nesting grassland songbirds, we demonstrate a novel approach to estimate hail-induced mortality. We quantify the relationship between the probability of nests destroyed by hail and measured Level-III Next Generation Radar (NEXRAD) data, including atmospheric base reflectivity, maximum estimated size of hail and maximum estimated azimuthal wind shear. On 22 June 2014, a hailstorm in northern Colorado destroyed 102 out of 203 known nests within our research site. Lark bunting ( Calamospiza melanocorys ) nests comprised most of the sample ( n = 186). Destroyed nests were more likely to be found in areas of higher storm intensity, and distributions of NEXRAD variables differed between failed and surviving nests. For 133 ground nests where nest-site vegetation was measured, we examined the ameliorative influence of woody vegetation, nest cover and vegetation density by comparing results for 13 different logistic regression models incorporating the independent and additive effects of weather and vegetation variables. The most parsimonious model used only the interactive effect of hail size and wind shear to predict the probability of nest survival, and the data provided no support for any of the models without this predictor. We conclude that vegetation structure may not mitigate mortality from severe hailstorms and that weather radar products can be used remotely to estimate potential for hail mortality of nesting grassland birds. These insights will improve the efficacy of grassland bird population models under predicted climate change scenarios.

Remote Sensing in Ecology and Conservation↗