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Results for “Winging It”

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USGS2004

Estimating disturbance effects from military training using developmental instability and physiological measures of plant stress

We used developmental instability, water potential, and variable fluorescence to determine if populations of winged sumac (Rhus copallinum) were being negatively effected by military training disturbance. We established nine sites that represented a land-use disturbance gradient with three impact levels (low, medium, and high), the effects mostly due to mechanized infantry training maneuvers. Although mean values of developmental instability, water potential, and variable fluorescence differed significantly among sites, the patterns did not consistently differentiate sites relative to the disturbance gradient. At the population level, some measures of developmental instability and variable fluorescence were positively correlated. All nine sites consisted of habitat mosaics, with the abundance of higher quality habitat patches and canopy gaps closely related to habitat impacts. It may be that R. copallinum is selecting similar micro-environments at all sites and therefore minimizing inter-site variation in stress measures, despite large differences in overall habitat condition. Our results call for caution in developing ecological indicators using the response of physiological and morphological measures from a single plant species. ?? 2003 Elsevier Ltd. All rights reserved.

Ecological Indicators↗

USGS2006

Balancing predation and egg harvest in a colonial seabird: A simulation model

We developed an individual-based model to study the effects of different regimes of harvesting eggs and natural predation on reproductive success in a colony of the glaucous-winged gull ( Larus glaucescens ) in Glacier Bay National Park, Alaska. The model incorporates the sequence of egg laying, relaying, and incubation to hatching for individual nests and calculates hatching success, incubation length, and the total number of eggs laid (as a result of re-nesting and relaying) in all nests in the colony. Stochasticity is incorporated in the distribution of nest lay dates, predation rates, and nests attacked during predation and harvest events. We estimated parameter values by fitting the model to data collected at a small colony during 1999 and 2000 using maximum likelihood. We then simulated harvests and analyzed model predictions. Model outputs indicate that harvesting early, and at one time, provides a predictable take of eggs with the least impact to gulls.

Ecological Modelling↗

USGS2008

Simulating the impact of cholinesterase-inhibiting pesticides on non-target wildlife in irrigated crops

We present a simulation model for risk assessment of the impact of insecticide inhibitors of cholinesterase (ChE) applied in irrigated agricultural fields on non-target wildlife. The model, which we developed as a compartment model based on difference equations (??t = 1 h), consists of six submodels describing the dynamics of (1) insecticide application, (2) insecticide movement into floodable soil, (3) irrigation and rain, (4) insecticide dissolution in water, (5) foraging and insecticide intake from water, and (6) ChE inhibition and recovery. To demonstrate application of the model, we simulated historical and "worst-case" scenarios of the impact of ChE-inhibiting insecticides on white-winged doves (Zenaida asiatica) inhabiting natural brushland adjacent to cotton and sugarcane fields in the Lower Rio Grande Valley of Texas, USA. Only when a rain event occurred just after insecticide application did predicted levels of ChE inhibition surpass the diagnostic level of 20% exposure. The present model should aid in assessing the effect of ChE-inhibiting insecticides on ChE activity of different species that drink contaminated water from irrigated agricultural fields, and in identifying specific situations in which the juxtaposition of environmental conditions and management schemes could result in a high risk to non-target wildlife. ?? 2007 Elsevier B.V. All rights reserved.

Ecological Modelling↗

USGS2017

Season, molt, and body size influence mercury concentrations in grebes

We studied seasonal and physiological influences on mercury concentrations in western grebes (Aechmophorus occidentalis) and Clark's grebes (A. occidentalis) across 29 lakes and reservoirs in California, USA. Additionally, at three of these lakes, we conducted a time series study, in which we repeatedly sampled grebe blood mercury concentrations during the spring, summer, and early fall. Grebe blood mercury concentrations were higher among males (0.61 ± 0.12 μg/g ww) than females (0.52 ± 0.10 μg/g ww), higher among Clark's grebes (0.58 ± 0.12 μg/g ww) than western grebes (0.51 ± 0.10 μg/g ww), and exhibited a strong seasonal pattern (decreasing by 60% from spring to fall). Grebe blood THg concentrations exhibited a shallow, inverse U-shaped pattern with body size, and was lowest among the smallest and largest grebes. Further, the relationship between grebe blood mercury concentrations and wing primary feather molt exhibited a shallow U-shaped pattern, where mercury concentrations were highest among birds that had not yet begun molting, decreased approximately 24% between pre-molt and late molt, and increased approximately 19% from late molt to post-molt. Because grebes did not begin molting until mid-summer, lower grebe blood mercury concentrations observed in late summer and early fall were consistent with the onset of primary feather molt. However, because sampling date was a much stronger predictor of grebe mercury concentrations than molt, other seasonally changing environmental factors likely played a larger role than molt in the seasonal variation in grebe mercury concentrations. In the time series study, we found that seasonal trends in grebe mercury concentrations were not consistent among lakes, indicating that lake-specific variation in mercury dynamics influence the overall seasonal decline in grebe blood mercury concentrations. These results highlight the importance of accounting for sampling date, as well as ecological processes that may influence mercury concentrations, when developing monitoring programs to assess site-specific exposure risk of mercury to wildlife.

California↗

USGS2010

Change in avian abundance predicted from regional forest inventory data

An inability to predict population response to future habitat projections is a shortcoming in bird conservation planning. We sought to predict avian response to projections of future forest conditions that were developed from nationwide forest surveys within the Forest Inventory and Analysis (FIA) program. To accomplish this, we evaluated the historical relationship between silvicolous bird populations and FIA-derived forest conditions within 25 ecoregions that comprise the southeastern United States. We aggregated forest area by forest ownership, forest type, and tree size-class categories in county-based ecoregions for 5 time periods spanning 1963-2008. We assessed the relationship of forest data with contemporaneous indices of abundance for 24 silvicolous bird species that were obtained from Breeding Bird Surveys. Relationships between bird abundance and forest inventory data for 18 species were deemed sufficient as predictive models. We used these empirically derived relationships between regional forest conditions and bird populations to predict relative changes in abundance of these species within ecoregions that are anticipated to coincide with projected changes in forest variables through 2040. Predicted abundances of these 18 species are expected to remain relatively stable in over a quarter (27%) of the ecoregions. However, change in forest area and redistribution of forest types will likely result in changed abundance of some species within many ecosystems. For example, abundances of 11 species, including pine warbler (Dendroica pinus), brown-headed nuthatch (Sitta pusilla), and chuckwills- widow (Caprimulgus carolinensis), are projected to increase within more ecoregions than ecoregions where they will decrease. For 6 other species, such as blue-winged warbler (Vermivora pinus), Carolina wren (Thryothorus ludovicianus), and indigo bunting (Passerina cyanea), we projected abundances will decrease within more ecoregions than ecoregions where they will increase.

Forest Ecology and Management↗

USGS2019

Assessing patterns of annual change to permafrost bluffs along the North Slope coast of Alaska using high-resolution imagery and elevation models

Coastal permafrost bluffs at Barter Island, on the North Slope, Beaufort Sea Coast of Alaska are among the most rapidly eroding along Alaska’s coast, having retreated up to 132 m between 1955 and 2015. Here we quantify rates and patterns of change over a single year using very-high resolution orthophotomosaics and co-registered surface elevation models derived from a survey-grade form of structure-from-motion photogrammetry from a fixed-wing, manned aircraft. The resulting elevation models were validated with over 10,000 ground check points and found that 95% agreed to within 20 cm, before accounting for real differences in the ground surface due to seasonality, vegetation, and checkpoint acquisition errors. This data set provides the most detailed and accurate measurements of coastal change to date along the Alaskan coast and the method is scaleable to more extensive coastlines. Between July 2014 and July 2015, the bluffs retreated an average of 1.3 m, and a maximum of 8.1 m, with an associated net volume loss of 38,100 ± 300 m3 (1.3 m3/m). This average retreat over this single year was slightly less than the 60-year mean rate of change of -1.5±0.1 m/yr, suggesting the 2014-2015 year represented relatively typical to slightly below average conditions. Most of the bluff material (70%) was lost during the 3 summer months (July to Sept) of 2014 and the remaining 30% between the late-summer and following winter-spring. The pattern of change was predominantly landward retreat of the top of the bluffs, removal of the debris apron and subsequent niching at the base of the bluffs during mid to late summer (July to Sept) followed by erosion of the bluff face and deposition of debris at the base of the bluff through the remainder of the year (Sept to the following July). Drivers of the observed change are likely a combination of thermal erosion on the bluff face throughout the summer and episodic thermo-mechanical removal of material, niching, and undercutting of the base associated with high-water levels driven by low-pressure storms and westerly winds. These patterns and high rates of change are believed to be broadly representative of coastal permafrost bluffs found along many high-latitude coastlines worldwide.

Alaska↗

USGS2021

Domoic acid and saxitoxin in seabirds in the United States between 2007 and 2018

As harmful algal blooms (HABs) increase in magnitude and duration worldwide, they are becoming an expanding threat to marine wildlife. Over the past decade, blooms of algae that produce the neurotoxins domoic acid (DA) and saxitoxin (STX) and documented concurrent seabird mortality events have increased bicoastally in the United States. We conducted a retrospective analysis of HAB related mortality events in California, Washington, and Rhode Island between 2007 and 2018 involving 12 species of seabirds, to document the levels, ranges, and patterns of DA and STX in eight sample types (kidney, liver, stomach, intestinal, cloacal, cecal contents, bile, blood) collected from birds during these events. Samples ( n = 182 ) from 83 birds were examined for DA ( n = 135) or STX ( n = 17) or both toxins simultaneously ( n = 30), using ELISA or LCMS at the National Oceanographic and Atmospheric Administration, National Marine Fisheries Service (NOAA-NMFS) Wildlife Algal-toxin Research and Response Network (WARRN-West) or the University of California, Santa Cruz (UCSC). DA or STX was detected in seven of the sample types with STX below the minimum detection limit in blood for the three samples tested. DA was found in 70% and STX was found in 23% of all tested samples. The ranges of detectable levels of DA and STX in all samples were 0.65–681,190.00 ng g −1 and 2.00–20.95 ng g −1 , respectively. Cloacal contents from a Pacific loon ( Gavia pacifica ) collected in 2017 from Ventura County, California, had the highest maximum level of DA for all samples and species tested in this study. The highest level of STX for all samples and species was detected in the bile of a northern fulmar ( Fulmarus glacialis ) collected in 2018 from San Luis Obispo County, California. DA detections were consistently found in gastrointestinal samples, liver, bile, and kidney, whereas STX detections were most frequently seen in liver and bile samples. Co-occurring HAB toxins (DA and STX) were detected in white-winged scoters ( Melanitta deglandi ) in 2009, a Brandt's cormorant ( Phalacrocorax penicillatus ) in 2015, and a northern fulmar and common murre ( Uria aalge ) in 2018. This article provides DA and STX tissue concentrations and patterns in avian samples and shows the utility of various sample types for the detection of HAB toxins. Future research to understand the pharmacodynamics of these toxins in avian species and to establish lethal doses in various bird species would be beneficial.

Harmful Algae↗

USGS2016

Gut content analysis of Lake Michigan waterbirds in years with avian botulism type E mortality, 2010–2012

Waterbird die-offs caused by Clostridium botulinum neurotoxin type E (BoNT/E) have occurred sporadically in the Great Lakes since the late 1960s, with a recent pulse starting in the late 1990s. In recent die-offs, round gobies ( Neogobius melanostomus ) have been implicated as vectors for the transfer of BoNT/E to fish-eating birds due to the round goby invasion history and their importance as prey. Dreissenid mussels ( Dreissena spp.) are also potentially involved in BoNT/E transmission to birds and round gobies. We examined gut contents of waterbirds collected in Lake Michigan during die-offs in 2010–2012, and the gut contents of culled, presumably BoNT/E-free double-crested cormorants ( Phalacrocorax auritus ). Round gobies were found in 86% of the BoNT/E-positive individuals, 84% of the BoNT/E-negative birds, and 94% of the BoNT/E-free cormorants examined. Double-crested cormorants, ring-billed gulls ( Larus delewarensis ), and common loons ( Gavia immer ) consumed larger-sized round gobies than horned and red-necked grebes ( Podiceps auritus and Podiceps grisegena ), white-winged scoters ( Melanitta deglandi ), and long-tailed ducks ( Clangula hymealis ). Other common prey included dreissenid mussels, terrestrial insects, and alewives ( Alosa pseudoharengus ). Our data emphasize the importance of round gobies and mussels in diets of Lake Michigan waterbirds and suggest they may play a role in the transfer of BoNT/E to waterbirds; however, round gobies and mussels were found in BoNT/E-positive, -negative, and -free individuals, suggesting that other factors, such as alternative trophic pathways for toxin transfer, bird migratory timing and feeding locations, prey behavior, and individual physiological differences across birds may affect the likelihood that a bird will succumb to BoNT/E intoxication.

Journal of Great Lakes Research↗

USGS2013

Photogrammetric monitoring of lava dome growth during the 2009 eruption of Redoubt Volcano

The 2009 eruption of Redoubt Volcano, Alaska, began with a phreatic explosion on 15 March followed by a series of at least 19 explosive events and growth and destruction of at least two, and likely three, lava domes between 22 March and 4 April. On 4 April explosive activity gave way to continuous lava effusion within the summit crater. We present an analysis of post-4 April lava dome growth using an oblique photogrammetry approach that provides a safe, rapid, and accurate means of measuring dome growth. Photogrammetric analyses of oblique digital images acquired during helicopter observation flights and fixed-wing volcanic gas surveys produced a series of digital elevation models (DEMs) of the lava dome from 16 April to 23 September. The DEMs were used to calculate estimates of volume and time-averaged extrusion rates and to quantify morphological changes during dome growth. Effusion rates ranged from a maximum of 35 m 3 s − 1 during the initial two weeks to a low of 2.2 m 3 s − 1 in early summer 2009. The average effusion rate from April to July was 9.5 m 3 s − 1 . Early, rapid dome growth was characterized by extrusion of blocky lava that spread laterally within the summit crater. In mid-to-late April the volume of the dome had reached 36 × 10 6 m 3 , roughly half of the total volume, and dome growth within the summit crater began to be limited by confining crater walls to the south, east, and west. Once the dome reached the steep, north-sloping gorge that breaches the crater, growth decreased to the south, but the dome continued to inflate and extend northward down the gorge. Effusion slowed during 16 April–1 May, but in early May the rate increased again. This rate increase was accompanied by a transition to exogenous dome growth. From mid-May to July the effusion rate consistently declined. The decrease is consistent with observations of reduced seismicity, gas emission, and thermal anomalies, as well as declining rates of geodetic deflation or inflation. These trends suggest dome growth ceased by July 2009. The volume of the dome at the end of the 2009 eruption was about 72 × 10 6 m 3 , more than twice the estimated volume of the largest dome extruded during the 1989–1990 eruption. In total, the 2009 dome extends over 400 m down the glacial gorge on the north end of the crater, with a total length of 1 km, width of 500 m and an average thickness of 200 m.

Alaska↗

USGS2013

Rapid chemical evolution of tropospheric volcanic emissions from Redoubt Volcano, Alaska, based on observations of ozone and halogen-containing gases

We report results from an observational and modeling study of reactive chemistry in the tropospheric plume emitted by Redoubt Volcano, Alaska. Our measurements include the first observations of Br and I degassing from an Alaskan volcano, the first study of O 3 evolution in a volcanic plume, as well as the first detection of BrO in the plume of a passively degassing Alaskan volcano. This study also represents the first detailed spatially-resolved comparison of measured and modeled O 3 depletion in a volcanic plume. The composition of the plume was measured on June 20, 2010 using base-treated filter packs (for F, Cl, Br, I, and S) at the crater rim and by an instrumented fixed-wing aircraft on June 21 and August 19, 2010. The aircraft was used to track the chemical evolution of the plume up to ~ 30 km downwind (2 h plume travel time) from the volcano and was equipped to make in situ observations of O 3 , water vapor, CO 2 , SO 2 , and H 2 S during both flights plus remote spectroscopic observations of SO 2 and BrO on the August 19th flight. The airborne data from June 21 reveal rapid chemical O 3 destruction in the plume as well as the strong influence chemical heterogeneity in background air had on plume composition. Spectroscopic retrievals from airborne traverses made under the plume on August 19 show that BrO was present ~ 6 km downwind (20 min plume travel time) and in situ measurements revealed several ppbv of O 3 loss near the center of the plume at a similar location downwind. Simulations with the PlumeChem model reproduce the timing and magnitude of the observed O 3 deficits and suggest that autocatalytic release of reactive bromine and in-plume formation of BrO were primarily responsible for the observed O 3 destruction in the plume. The measurements are therefore in general agreement with recent model studies of reactive halogen formation in volcanic plumes, but also show that field studies must pay close attention to variations in the composition of ambient air entrained into volcanic plumes in order to unambiguously attribute observed O 3 anomalies to specific chemical or dynamic processes. Our results suggest that volcanic eruptions in Alaska are sources of reactive halogen species to the subarctic troposphere.

Alaska↗

USGS2011

Interspecies transmission and limited persistence of low pathogenic avian influenza genomes among Alaska dabbling ducks

The reassortment and geographic distribution of low pathogenic avian influenza (LPAI) virus genes are well documented, but little is known about the persistence of intact LPAI genomes among species and locations. To examine persistence of entire LPAI genome constellations in Alaska, we calculated the genetic identities among 161 full-genome LPAI viruses isolated across 4 years from five species of duck: northern pintail ( Anas acuta ), mallard ( Anas platyrhynchos ), American green-winged teal ( Anas crecca ), northern shoveler ( Anas clypeata ) and American wigeon ( Anas americana ). Based on pairwise genetic distance, highly similar LPAI genomes (>99% identity) were observed within and between species and across a range of geographic distances (up to and >1000 km), but most often between isolates collected 0–10 km apart. Highly similar viruses were detected between years, suggesting inter-annual persistence, but these were rare in our data set with the majority occurring within 0–9 days of sampling. These results identify LPAI transmission pathways in the context of species, space and time, an initial perspective into the extent of regional virus distribution and persistence, and insight into why no completely Eurasian genomes have ever been detected in Alaska. Such information will be useful in forecasting the movement of foreign-origin avian influenza strains should they be introduced to North America.

Alaska↗

USGS2009

Developmental toxicity in white leghorn chickens following in ovo exposure to perfluorooctane sulfonate (PFOS)

Studies show that perfluorinated compounds cause various toxicological effects; nevertheless, effects on immune function and developmental endpoints have not been addressed at length. This study examined the effects of perfluorooctane sulfonate (PFOS) in white leghorn hatchlings on various developmental, immunological, and clinical health parameters. In addition, serum PFOS concentrations were determined by LC/MS/MS. Embryonic day (ED) 0 eggs were injected with either safflower oil/10% DMSO (control, 0 mg/kg egg wt) or PFOS in safflower oil/10% DMSO at 1, 2.5, or 5 mg/kg egg wt, and the chicks were grown to post-hatch day (PHD) 14. Treatment with PFOS did not affect hatch rate. Following in ovo exposure chicks exhibited increases in spleen mass at all treatment levels, in liver mass at 2.5 and 5 mg/kg egg wt, and in body length (crown-rump length) at the 5 mg/kg treatment. Right wings were shorter in all treatments compared to control. Increases in the frequency of brain asymmetry were evident in all treatment groups. SRBC-specific immunoglobulin (IgM and IgY combined) titers were decreased significantly at all treatment levels, while plasma lysozyme activity was increased at all treatment levels. The PHA skin test response decreased in relation to increasing PFOS dose. Serum concentrations where significant immunological, morphological, and neurological effects were observed at the lowest dose (1 mg/kg egg wt) averaged 154 ng PFOS/g serum. These concentrations fall within environmental ranges reported in blood samples from wild caught avian species; thereby, verifying that the environmental egg concentrations used for the injections do indeed relate to serum levels in hatchlings that are also environmentally relevant. These data indicate that immune alterations and brain asymmetry can occur in birds following in ovo exposure to environmentally relevant concentrations of PFOS and demonstrates the need for further research on the developmental effects of perfluorinated compounds in various species. ?? 2009 Elsevier Inc.

Reproductive Toxicology↗

USGS2011

Thematic accuracy of the National Land Cover Database (NLCD) 2001 land cover for Alaska

The National Land Cover Database (NLCD) 2001 Alaska land cover classification is the first 30-m resolution land cover product available covering the entire state of Alaska. The accuracy assessment of the NLCD 2001 Alaska land cover classification employed a geographically stratified three-stage sampling design to select the reference sample of pixels. Reference land cover class labels were determined via fixed wing aircraft , as the high resolution imagery used for determining the reference land cover classification in the conterminous U.S. was not available for most of Alaska. Overall thematic accuracy for the Alaska NLCD was 76.2% (s.e. 2.8%) at Level II (12 classes evaluated) and 83.9% (s.e. 2.1%) at Level I (6 classes evaluated) when agreement was defined as a match between the map class and either the primary or alternate reference class label. When agreement was defined as a match between the map class and primary reference label only, overall accuracy was 59.4% at Level II and 69.3% at Level I. The majority of classification errors occurred at Level I of the classification hierarchy (i.e., misclassifications were generally to a different Level I class, not to a Level II class within the same Level I class). Classification accuracy was higher for more abundant land cover classes and for pixels located in the interior of homogeneous land cover patches.

Alaska↗

USGS2014

Fitting statistical distributions to sea duck count data: implications for survey design and abundance estimation

Determining appropriate statistical distributions for modeling animal count data is important for accurate estimation of abundance, distribution, and trends. In the case of sea ducks along the U.S. Atlantic coast, managers want to estimate local and regional abundance to detect and track population declines, to define areas of high and low use, and to predict the impact of future habitat change on populations. In this paper, we used a modified marked point process to model survey data that recorded flock sizes of Common eiders, Long-tailed ducks, and Black, Surf, and White-winged scoters. The data come from an experimental aerial survey, conducted by the United States Fish & Wildlife Service (USFWS) Division of Migratory Bird Management, during which east-west transects were flown along the Atlantic Coast from Maine to Florida during the winters of 2009–2011. To model the number of flocks per transect (the points), we compared the fit of four statistical distributions (zero-inflated Poisson, zero-inflated geometric, zero-inflated negative binomial and negative binomial) to data on the number of species-specific sea duck flocks that were recorded for each transect flown. To model the flock sizes (the marks), we compared the fit of flock size data for each species to seven statistical distributions: positive Poisson, positive negative binomial, positive geometric, logarithmic, discretized lognormal, zeta and Yule–Simon. Akaike’s Information Criterion and Vuong’s closeness tests indicated that the negative binomial and discretized lognormal were the best distributions for all species for the points and marks, respectively. These findings have important implications for estimating sea duck abundances as the discretized lognormal is a more skewed distribution than the Poisson and negative binomial, which are frequently used to model avian counts; the lognormal is also less heavy-tailed than the power law distributions (e.g., zeta and Yule–Simon), which are becoming increasingly popular for group size modeling. Choosing appropriate statistical distributions for modeling flock size data is fundamental to accurately estimating population summaries, determining required survey effort, and assessing and propagating uncertainty through decision-making processes.

Statistical Methodology↗

USGS2002

Environmental contaminants in prey and tissues of the peregrine falcon in the Big Bend Region, Texas, USA.

Peregrine falcons ( Falco peregrinus ) have been recorded nesting in Big Bend National Park, Texas, USA and other areas of the Chihuahuan Desert since the early 1900s. From 1993 to 1996, peregrine falcon productivity rates were very low and coincided with periods of low rainfall. However, low productivity also was suspected to be caused by environmental contaminants. To evaluate potential impacts of contaminants on peregrine falcon populations, likely avian and bat prey species were collected during 1994 and 1997 breeding seasons in selected regions of western Texas, primarily in Big Bend National Park. Tissues of three peregrine falcons found injured or dead and feathers of one live fledgling also were analyzed. Overall, mean concentrations of DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], a metabolite of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane], were low in all prey species except for northern rough-winged swallows ( Stelgidopteryx serripennis , mean = 5.1 microg/g ww). Concentrations of mercury and selenium were elevated in some species, up to 2.5 microg/g dw, and 15 microg/g dw, respectively, which upon consumption could seriously affect reproduction of top predators. DDE levels near 5 microg/g ww were detected in carcass of one peregrine falcon found dead but the cause of death was unknown. Mercury, selenium, and DDE to some extent, may be contributing to low reproductive rates of peregrine falcons in the Big Bend region.

Texas↗

USGS2011

Bird mercury concentrations change rapidly as chicks age: Toxicological risk is highest at hatching and fledging

Toxicological risk of methylmercury exposure to juvenile birds is complex due to the highly transient nature of mercury concentrations as chicks age. We examined total mercury and methylmercury concentrations in blood, liver, kidney, muscle, and feathers of 111 Forster's tern (Sterna forsteri), 69 black-necked stilt (Himantopus mexicanus), and 43 American avocet (Recurvirostra americana) chicks as they aged from hatching through postfledging at wetlands that had either low or high mercury contamination in San Francisco Bay, California. For each waterbird species, internal tissue, and wetland, total mercury and methylmercury concentrations changed rapidly as chicks aged and exhibited a quadratic, U-shaped pattern from hatching through postfledging. Mercury concentrations were highest immediately after hatching, due to maternally deposited mercury in eggs, then rapidly declined as chicks aged and diluted their mercury body burden through growth in size and mercury depuration into growing feathers. Mercury concentrations then increased during fledging when mass gain and feather growth slowed, while chicks continued to acquire dietary mercury. In contrast to mercury in internal tissues, mercury concentrations in chick feathers were highly variable and declined linearly with age. For 58 recaptured Forster's tern chicks, the proportional change in blood mercury concentration was negatively related to the proportional change in body mass, but not to the amount of feathers or wing length. Thus, mercury concentrations declined more in chicks that gained more mass between sampling events. The U-shaped pattern of mercury concentrations from hatching to fledging indicates that juvenile birds may be at highest risk to methylmercury toxicity shortly after hatching when maternally deposited mercury concentrations are still high and again after fledging when opportunities for mass dilution and mercury excretion into feathers are limited.

Environmental Science & Technology↗

USGS2014

Metamorphosis enhances the effects of metal exposure on the mayfly, Centroptilum triangulifer

The response of larval aquatic insects to stressors such as metals is used to assess the ecological condition of streams worldwide. However, nearly all larval insects metamorphose from aquatic larvae to winged adults, and recent surveys indicate that adults may be a more sensitive indicator of stream metal toxicity than larvae. One hypothesis to explain this pattern is that insects exposed to elevated metal in their larval stages have a reduced ability to successfully complete metamorphosis. To test this hypothesis we exposed late-instar larvae of the mayfly, Centroptilum triangulifer , to an aqueous Zn gradient (32–476 μg/L) in the laboratory. After 6 days of exposure, when metamorphosis began, larval survival was unaffected by zinc. However, Zn reduced wingpad development at concentrations above 139 μg/L. In contrast, emergence of subimagos and imagos tended to decline with any increase in Zn. At Zn concentrations below 105 μg/L (hardness-adjusted aquatic life criterion), survival between the wingpad and subimago stages declined 5-fold across the Zn gradient. These results support the hypothesis that metamorphosis may be a survival bottleneck, particularly in contaminated streams. Thus, death during metamorphosis may be a key mechanism explaining how stream metal contamination can impact terrestrial communities by reducing aquatic insect emergence.

Environmental Science & Technology↗

USGS1997

Habitat use and movements of shovelnose sturgeon in Pool 13 of the upper Mississippi River during extreme low flow conditions

We monitored habitat use and movement of 27 adult shovelnose sturgeon in Pool 13 of the upper Mississippi River, Iowa-Illinois, by radio-telemetry in April through August 1988. Our objective was to determine the response of this species to unusually low water conditions in the upper Mississippi River in 1988. Most (94%) telemetry contacts were made in 3 habitat types: main channel (50%), main channel border where wing dams were present (29%), and tailwaters of Lock and Dam 12 (15%). Habitat use in spring was affected by the extreme low flows. We often found tagged shovelnose sturgeon in the main channel and tailwaters during the spring period (11 March–20 May) where water velocities were highest. This was in contrast to other studies where shovelnose sturgeon did not occupy those areas during years with normal spring flows. Shovelnose sturgeon were typically found in areas with a sand bottom, mean water depth of 5.8 m, and mean bottom current velocity of 0.23 m sec -1 . They occupied areas of swifter current but were not always found in the fastest current in their immediate vicinity. Tagged shovelnose sturgeon tended to remain in the upper, more riverine portion of the pool, and we observed no emigration from the study pool. Linear total range of movement from the tagging site ranged from 1.9 to 54.6 km during the study period.

Illinois;Iowa↗