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USGS2010

Changes in the timing of snowmelt and streamflow in Colorado: A response to recent warming

Trends in the timing of snowmelt and associated runoff in Colorado were evaluated for the 1978-2007 water years using the regional Kendall test (RKT) on daily snow-water equivalent (SWE) data from snowpack telemetry (SNOTEL) sites and daily streamflow data from headwater streams. The RKT is a robust, nonparametric test that provides an increased power of trend detection by grouping data from multiple sites within a given geographic region. The RKT analyses indicated strong, pervasive trends in snowmelt and streamflow timing, which have shifted toward earlier in the year by a median of 2-3 weeks over the 29-yr study period. In contrast, relatively few statistically significant trends were detected using simple linear regression. RKT analyses also indicated that November-May air temperatures increased by a median of 0.9 degrees C decade -1 , while 1 April SWE and maximum SWE declined by a median of 4.1 and 3.6 cm decade -1 , respectively. Multiple linear regression models were created, using monthly air temperatures, snowfall, latitude, and elevation as explanatory variables to identify major controlling factors on snowmelt timing. The models accounted for 45% of the variance in snowmelt onset, and 78% of the variance in the snowmelt center of mass (when half the snowpack had melted). Variations in springtime air temperature and SWE explained most of the interannual variability in snowmelt timing. Regression coefficients for air temperature were negative, indicating that warm temperatures promote early melt. Regression coefficients for SWE, latitude, and elevation were positive, indicating that abundant snowfall tends to delay snowmelt, and snowmelt tends to occur later at northern latitudes and high elevations. Results from this study indicate that even the mountains of Colorado, with their high elevations and cold snowpacks, are experiencing substantial shifts in the timing of snowmelt and snowmelt runoff toward earlier in the year.

Colorado↗

USGS2024

Event classification, seismicity, and eruption forecasting at Great Sitkin Volcano, Alaska: 1999–2023

The frequency content of volcanogenic seismicity is often used to classify events and their spatial and temporal progression is then used to map subsurface volcanic processes. The progression of volcano-seismic events and associated source processes also plays a critical role in eruption forecasting. Here we develop and evaluate a computerized methodology for characterizing volcano-seismic event types using Frequency Index and Average Peak Frequency. We apply and test this technique at Great Sitkin Volcano, Alaska, classifying over 9000 hypocenters between 1999 and 2023. This 24-year time span covers periods of seismic quiescence, earthquake activity on nearby tectonic (bookshelf) faults, precursory unrest from 2016 to 2021, and the explosive onset in May 2021 of the ongoing effusive eruption. We use the spatial and temporal evolution of classified event types to map the active volcanic and tectonic processes, develop a conceptual model of the subsurface magmatic system, and perform a retrospective analysis of eruption forecasts at Great Sitkin Volcano between 2016 and the present. The classification and progression of hypocenters suggests the subsurface Great Sitkin Volcano magmatic system consists of a mid- to lower- crustal source zone between 10 and 40 km depth and an upper crustal magma storage area between −1 and 10 km depth (hypocenter depth is referenced to sea level and negative depths reflect height above sea level). The earliest precursors occurred in July 2016 and consisted of deep long-period and volcano-tectonic earthquakes at mid-crustal depths suggesting the subsequent unrest and eruption were triggered by a deeper intrusion of magma. This mid-crustal seismic activity was immediately followed by the onset upper-crustal long-period events and volcano-tectonic earthquakes VTs suggesting a strong linkage between the shallow and deeper portions of the magmatic system. The upper crustal area was likely capped by the 1974 lava dome until the magmatic explosion on May 26, 2021.

Alaska↗

USGS2011

Evaluation of offshore stocking of Lake Trout in Lake Ontario

Restoration stocking of hatchery-reared lake trout Salvelinus namaycush has occurred in Lake Ontario since 1973. In U.S. waters, fish stocked through 1990 survived well and built a large adult population. Survival of yearlings stocked from shore declined during 1990–1995, and adult numbers fell during 1998–2005. Offshore stocking of lake trout was initiated in the late 1990s in response to its successful mitigation of predation losses to double-crested cormorants Phalacrocorax auritus and the results of earlier studies that suggested it would enhance survival in some cases. The current study was designed to test the relative effectiveness of three stocking methods at a time when poststocking survival for lake trout was quite low and losses due to fish predators was a suspected factor. The stocking methods tested during 2000–2002 included May offshore, May onshore, and June onshore. Visual observations during nearshore stockings and hydroacoustic observations of offshore stockings indicated that release methods were not a direct cause of fish mortality. Experimental stockings were replicated for 3 years at one site in the southwest and for 2 years at one site in the southeast. Offshore releases used a landing craft to transport hatchery trucks from 3 to 6 km offshore out to 55–60-m-deep water. For the southwest site, offshore stocking significantly enhanced poststocking survival. Among the three methods, survival ratios were 1.74 : 1.00 : 1.02 (May offshore : May onshore : June onshore). Although not statistically significant owing to the small samples, the trends were similar for the southeast site, with survival ratios of 1.67 : 1.00 : 0.72. Consistent trends across years and sites indicated that offshore stocking of yearling lake trout during 2000–2002 provided nearly a twofold enhancement in survival; however, this increase does not appear to be great enough to achieve the 12-fold enhancement necessary to return population abundance to restoration targets.

North American Journal of Fisheries Management↗

USGS2018

Avian keratin disorder of Alaska black-capped chickadees is associated with Poecivirus infection

Background Avian keratin disorder (AKD) is an epizootic of debilitating beak deformities, first documented in black-capped chickadees ( Poecile atricapillus ) in Alaska during the late 1990s. Similar deformities have now been recorded in dozens of species of birds across multiple continents. Despite this, the etiology of AKD has remained elusive, making it difficult to assess the impacts of this disease on wild populations. We previously identified an association between infection with a novel picornavirus, Poecivirus, and AKD in a small cohort of black-capped chickadees. Methods To test if the association between Poecivirus and AKD holds in a larger study population, we used targeted PCR followed by Sanger sequencing to screen 124 symptomatic and asymptomatic black-capped chickadees for Poecivirus infection. We further compared the efficacy of multiple non-terminal field sampling methods (buccal swabs, cloacal swabs, fecal samples, and blood samples) for Poecivirus screening. Finally, we used both in situ hybridization and a strand-specific expression assay to localize Poecivirus to beak tissue of AKD-positive individuals and to determine if virus is actively replicating in beak tissue. Results Poecivirus was detected in 28/28 (100%) individuals with AKD, but only 9/96 (9.4%) asymptomatic individuals with apparently normal beaks (p < 0.0001). We found that cloacal swabs are the most sensitive of these sample types for detecting Poecivirus in birds with AKD, but that buccal swabs should be combined with cloacal swabs in evaluating the infection status of asymptomatic birds. Finally, we used both in situ hybridization and a strand-specific expression assay to localize Poecivirus to beak tissue of AKD-positive individuals and to provide evidence of active viral replication. Conclusion The data presented here show a strong, statistically significant relationship between Poecivirus infection and AKD, and provide evidence that Poecivirus is indeed an avian virus, infecting and actively replicating in beak tissue of AKD-affected BCCH. Taken together, these data corroborate and extend the evidence for a potential causal association between Poecivirus and AKD in the black-capped chickadee. Poecivirus continues to warrant further investigation as a candidate agent of AKD.

Alaska↗

USGS2007

Seasonal variations in modern speleothem calcite growth in Central Texas, U.S.A

Variations in growth rates of speleothem calcite have been hypothesized to reflect changes in a range of paleoenvironmental variables, including atmospheric temperature and precipitation, drip-water composition, and the rate of soil CO2 delivery to the subsurface. To test these hypotheses, we quantified growth rates of modern speleothem calcite on artificial substrates and monitored concurrent environmental conditions in three caves across the Edwards Plateau in central Texas. Within each of two caves, different drip sites exhibit similar annual cycles in calcite growth rates, even though there are large differences between the mean growth rates at the sites. The growth-rate cycles inversely correlate to seasonal changes in regional air temperature outside the caves, with near-zero growth rates during the warmest summer months, and peak growth rates in fall through spring. Drip sites from caves 130 km apart exhibit similar temporal patterns in calcite growth rate, indicating a controlling mechanism on at least this distance. The seasonal variations in calcite growth rate can be accounted for by a primary control by regional temperature effects on ventilation of cave-air CO2 concentrations and/or drip-water CO2 contents. In contrast, site-to-site differences in the magnitude of calcite growth rates within an individual cave appear to be controlled principally by differences in drip rate. A secondary control by drip rate on the growth rate temporal variations is suggested by interannual variations. No calcite growth was observed in the third cave, which has relatively high values of and small seasonal changes in cave-air CO2. These results indicate that growth-rate variations in ancient speleothems may serve as a paleoenvironmental proxy with seasonal resolution. By applying this approach of monitoring the modern system, speleothem growth rate and geochemical proxies for paleoenviromnental change may be evaluated and calibrated. Copyright ?? 2007, SEPM (Society for Sedimentary Geology).

Journal of Sedimentary Research↗

USGS2003

A comparison of measures of riverbed form for evaluating distributions of benthic fishes

A method to quantitatively characterize the bed forms of a large river and a preliminary test of the relationship between bed-form characteristics and catch per unit area of benthic fishes is presented. We used analog paper recordings of bathymetric data from the Missouri River and fish data collected from 1996 to 1998 at both the segment (???101-102-km) and macrohabitat (???10-1-100-km) spatial scales. Bed-form traces were transformed to digital data with image analysis software. The slope, mean residual, and SD of the residuals of the regression of depth versus distance along the bottom, as well as mean depth, were estimated for each trace. These four metrics were compared with sinuosity, fractal dimension, critical scale, and maximum mean angle for the same traces. Mean depth and sinuosity differed among segments and macrohabitats. Fractal-based measures of the relative depth of bottom troughs (critical scale) and smoothness (maximum mean angle) differed among segments. Statistics-based measures of the relative depth of bottom troughs (mean residual) and smoothness (SD of the residuals) differed among macrohabitats. Sites with shovelnose sturgeon Scaphirhynchus platorynchus were shallower and smoother than sites without shovelnose sturgeon. When compared with sites without sicklefin chub Macrhybopsis meeki, sites with sicklefin chub were shallower, had shallower troughs, and sloped more out of the flow of the river. Sites with sturgeon chub M. gelida were shallower, had shallower troughs, and were smoother than sites without sturgeon chub. Sites with and without channel catfish Ictalurus punctatus did not differ for any bed-form variables measured. Nonzero shovelnose sturgeon density increased with depth, whereas nonzero sturgeon chub density decreased with depth. Indices of bed-form structure demonstrated potential for describing the distribution and abundance of Missouri River benthic fishes. The observed fish patterns, though limited, provide valuable direction for future research into the habitat preferences of these fishes.

North American Journal of Fisheries Management↗

USGS2004

Evaluating mallard adaptive management models with time series

Wildlife practitioners concerned with midcontinent mallard ( Anas platyrhynchos ) management in the United States have instituted a system of adaptive harvest management (AHM) as an objective format for setting harvest regulations. Under the AHM paradigm, predictions from a set of models that reflect key uncertainties about processes underlying population dynamics are used in coordination with optimization software to determine an optimal set of harvest decisions. Managers use comparisons of the predictive abilities of these models to gauge the relative truth of different hypotheses about density-dependent recruitment and survival, with better-predicting models giving more weight to the determination of harvest regulations. We tested the effectiveness of this strategy by examining convergence rates of 'predictor' models when the true model for population dynamics was known a priori. We generated time series for cases when the a priori model was 1 of the predictor models as well as for several cases when the a priori model was not in the model set. We further examined the addition of different levels of uncertainty into the variance structure of predictor models, reflecting different levels of confidence about estimated parameters. We showed that in certain situations, the model-selection process favors a predictor model that incorporates the hypotheses of additive harvest mortality and weakly density-dependent recruitment, even when the model is not used to generate data. Higher levels of predictor model variance led to decreased rates of convergence to the model that generated the data, but model weight trajectories were in general more stable. We suggest that predictive models should incorporate all sources of uncertainty about estimated parameters, that the variance structure should be similar for all predictor models, and that models with different functional forms for population dynamics should be considered for inclusion in predictor model sets. All of these suggestions should help lower the probability of erroneous learning in mallard ABM and adaptive management in general.

Journal of Wildlife Management↗

USGS2005

Plant-based plume-scale mapping of tritium contamination in desert soils

Plant-based techniques were tested for field-scale evaluation of tritium contamination adjacent to a low-level radioactive waste (LLRW) facility in the Amargosa Desert, Nevada. Objectives were to (i) characterize and map the spatial variability of tritium in plant water, (ii) develop empirical relations to predict and map subsurface contamination from plant-water concentrations, and (iii) gain insight into tritium migration pathways and processes. Plant sampling [creosote bush, Larrea tridentata (Sessé & Moc. ex DC.) Coville] required one-fifth the time of soil water vapor sampling. Plant concentrations were spatially correlated to a separation distance of 380 m; measurement uncertainty accounted for <0.1% of the total variability in the data. Regression equations based on plant tritium explained 96 and 90% of the variation in root-zone and sub-root-zone soil water vapor concentrations, respectively. The equations were combined with kriged plant-water concentrations to map subsurface contamination. Mapping showed preferential lateral movement of tritium through a dry, coarse-textured layer beneath the root zone, with concurrent upward movement through the root zone. Analysis of subsurface fluxes along a transect perpendicular to the LLRW facility showed that upward diffusive-vapor transport dominates other transport modes beneath native vegetation. Downward advective-liquid transport dominates at one endpoint of the transect, beneath a devegetated road immediately adjacent to the facility. To our knowledge, this study is the first to document large-scale subsurface vapor-phase tritium migration from a LLRW facility. Plant-based methods provide a noninvasive, cost-effective approach to mapping subsurface tritium migration in desert areas.

Vadose Zone Journal↗

USGS2014

Effectiveness of Aquaflor (50% florfenicol) administered in feed to control mortality associated with Streptococcus iniae in tilapia at a commercial tilapia production facility

The efficacy of Aquaflor (florfenicol; FFC) to control mortality caused by Streptococcus iniae in tilapia was evaluated under field conditions. The trial was initiated following presumptive diagnosis of S. iniae infection in a mixed group of fingerling (mean, 4.5 g) Nile Tilapia Oreochromis niloticus and a hybrid of Nile Tilapia×Blue Tilapia O. aureus . Diagnoses included mortality in source tank; examination of clinical signs and presence or absence of gram-positive cocci in brain, and collection of samples for microbiological review and disease confirmation of 60 moribund fish. Following presumptive diagnosis, tilapia (83/tank) were randomly transferred to each of 20 test tanks receiving the same water as the source tank (test tank water was not reused). Tilapia were offered either nonmedicated control feed or FFC-medicated feed (FFC at 15 mg/kg body weight/d; 10 tanks per regimen) for 10 consecutive days followed by a 14-d observation period during which only the nonmedicated control feed was offered. Streptococcus iniae was presumptively identified during pretreatment necropsy and confirmed by polymerase chain reaction assay; S. iniae was confirmed in samples taken during the dosing period but was not detected during the postdosing period. The FFC disk diffusion zone of inhibition ranged from 29 to 32 mm, while the minimum inhibitory concentration of FFC ranged from 2 to 4 μg/mL for the S. iniae isolates collected. Survival of tilapia assigned to the FFC-dose group was significantly greater at 14 d posttreatment than that of the nonmedicated controls. The odds of tilapia assigned to the FFC-dose group surviving to the end of the postdosing period were 1.34 times the odds of survival of tilapia assigned to the nonmedicated control group. There were no clinically apparent adverse effects associated with the administration of FFC-medicated feed in this study.

North American Journal of Aquaculture↗

USGS1999

An evaluation of six internal anchor tags for tagging juvenile striped bass

Six types of internal anchor tags were compared for retention, legibility, and durability in tagging juvenile (age-0) striped bass Morone saxatilis . Tank-reared striped bass (120–200 mm total length) were tagged with coded wire tags and one of six types of internal anchor tags (500 fish each tag type and two groups of controls). The types of internal anchor tags used were as follows: Floy streamer FM-84 (currently in use by the U. S. Fish and Wildlife Service); Floy streamer with protective sheath (modified FM-84), Floy streamer with a monofilament leader and sheath (FM-89SL), modified Hallprint T687, Hallprint monofilament IEX WAD, and Hallprint T-bar IEX NOR. The Hallprint T-bar IEX NOR and the Floy FM-84 tags caused significantly higher 2-week and 6-month mortality. Final fish total length was different among tag types and tagger groups; however, final fish size was not correlated with either variable after adjusting for initial fish size. Tags were also mounted on polyvinyl chloride pipes and exposed to freshwater, brackish-water, and saltwater environments for 1 year. The brackish-water environment was harsher than either freshwater or salt water and had a greater density of fouling organisms. Legibility was poor for the Floy streamer, and Floy tag sheaths sometimes moved and obscured the printing. Failure rates (printing loss or tag loss) for the Floy tags (36%) were about six times higher than the Hallprint tags (6%). An analysis of 369 anchor tags returned by striped bass fishers indicated that the tag was illegible when more than 43 printed characters were lost and that illegibility increased over time. None of the tags tested was considered appropriate for tagging juvenile striped bass, but changes in tag design, material, and insertion could improve tag retention and survival.

North American Journal of Fisheries Management↗

USGS2013

Pathogen exposure and blood chemistry in the Washington population of northern sea otters (Enhydra lutris kenyoni)

Northern sea otters (Enhydra lutris kenyoni) from Washington State, United States were evaluated in 2011 to determine health status and pathogen exposure. Antibodies to Brucella spp. (10%) and influenza A virus (23%) were detected for the first time in this population in 2011. Changes in clinical pathology values (serum chemistries), exposure to pathogens, and overall health of the population over the last decade were assessed by comparing 2011 data to the data collected on this population in 2001–2002. Several serum chemistry parameters were different between study years and sexes but were not clinically significant. The odds of canine distemper virus exposure were higher for otters sampled in 2001–2002 (80%) compared to 2011 (10%); likelihood of exposure significantly increased with age. Prevalence of exposure to Sarcocystis neurona was also higher in 2001–2002 (29%) than in 2011 (0%), but because testing methods varied between study years the results were not directly comparable. Exposure to Leptospira spp. was only observed in 2001–2002. Odds of Toxoplasma gondii exposure were higher for otters sampled in 2011 (97%) than otters in 2001–2002 (58%). Substantial levels of domoic acid (n = 2) and saxitoxin (n = 2) were found in urine or fecal samples from animals sampled in 2011. No evidence of calicivirus or Coxiella burnetii exposure in the Washington population of northern sea otters was found in either 2001–2002 or 2011. Changes in exposure status from 2001–2002 to 2011 suggest that the Washington sea otter population may be dealing with new disease threats (e.g., influenza) while also increasing their susceptibility to diseases that may be highly pathogenic in naïve individuals (e.g., canine distemper).

Washington↗

USGS2008

Assessment of crop growth and soil water modules in SWAT2000 using extensive field experiment data in an irrigation district of the Yellow River Basin

SWAT, a physically-based, hydrological model simulates crop growth, soil water and groundwater movement, and transport of sediment and nutrients at both the process and watershed scales. While the different versions of SWAT have been widely used throughout the world for agricultural and water resources applications, little has been done to test the performance, variability, and transferability of the parameters in the crop growth, soil water, and groundwater modules in an integrated way with multiple sets of field experimental data at the process scale. Using an multiple years of field experimental data of winter wheat (Triticum aestivum L.) in the irrigation district of the Yellow River Basin, this paper assesses the performance of the plant-soil-groundwater modules and the variability and transferability of SWAT2000. Comparison of the simulated results by SWAT to the observations showed that SWAT performed quite unsatisfactorily in LAI predictions during the senescence stage, in yield predictions, and in soil-water estimation under dry soil-profile conditions. The unsatisfactory performance in LAI prediction might be attributed to over-simplified senescence modeling; in yield prediction to the improper computation of the harvest index; and in soil water under dry conditions to the exclusion of groundwater evaporation from the soil water balance in SWAT. In this paper, improvements in crop growth, soil water, and groundwater modules in SWAT were implemented. The saturated soil profile was coupled to the oscillating groundwater table. A variable evaporation coefficient taking into account soil water deficit index, groundwater depth, and crop root depth was used to replace the fixed coefficient in computing groundwater evaporation. The soil water balance included the groundwater evaporation. The modifications improved simulations of crop evapotranspiration and biomass as well as soil water dynamics under dry soil-profile conditions. The evaluation shows that the crop growth and soil water components of SWAT could be further refined to better simulate the hydrology of agricultural watersheds. ?? 2008 Elsevier B.V. All rights reserved.

Journal of Hydrology↗

USGS2018

A framework for identifying and characterising coral reef “oases” against a backdrop of degradation

Human activities have led to widespread ecological decline; however, the severity of degradation is spatially heterogeneous due to some locations resisting, escaping, or rebounding from disturbances. We developed a framework for identifying oases within coral reef regions using long‐term monitoring data. We calculated standardised estimates of coral cover ( z ‐scores) to distinguish sites that deviated positively from regional means. We also used the coefficient of variation (CV) of coral cover to quantify how oases varied temporally, and to distinguish among types of oases. We estimated “coral calcification capacity” (CCC), a measure of the coral community's ability to produce calcium carbonate structures and tested for an association between this metric and z ‐scores of coral cover. We illustrated our z ‐score approach within a modelling framework by extracting z ‐scores and CVs from simulated data based on four generalized trajectories of coral cover. We then applied the approach to time‐series data from long‐term reef monitoring programmes in four focal regions in the Pacific (the main Hawaiian Islands and Mo'orea, French Polynesia) and western Atlantic (the Florida Keys and St. John, US Virgin Islands). Among the 123 sites analysed, 38 had positive z ‐scores for median coral cover and were categorised as oases. Synthesis and applications . Our framework provides ecosystem managers with a valuable tool for conservation by identifying “oases” within degraded areas. By evaluating trajectories of change in state (e.g., coral cover) among oases, our approach may help in identifying the mechanisms responsible for spatial variability in ecosystem condition. Increased mechanistic understanding can guide whether management of a particular location should emphasise protection, mitigation or restoration. Analysis of the empirical data suggest that the majority of our coral reef oases originated by either escaping or resisting disturbances, although some sites showed a high capacity for recovery, while others were candidates for restoration. Finally, our measure of reef condition (i.e., median z ‐scores of coral cover) correlated positively with coral calcification capacity suggesting that our approach identified oases that are also exceptional for one critical component of ecological function.

Florida, Hawaii↗

USGS2010

Identifying sites for elk restoration in Arkansas

We used spatial data to identify potential areas for elk ( Cervus elaphus ) restoration in Arkansas. To assess habitat, we used locations of 239 elk groups collected from helicopter surveys in the Buffalo National River area of northwestern Arkansas, USA, from 1992 to 2002. We calculated the Mahalanobis distance ( D 2 ) statistic based on the relationship between those elk-group locations and a suite of 9 landscape variables to evaluate winter habitat in Arkansas. We tested model performance in the Buffalo National River area by comparing the D 2 values of pixels representing areas with and without elk pellets along 19 fixed-width transects surveyed in March 2002. Pixels with elk scat had lower D 2 values than pixels in which we found no pellets (logistic regression: Wald χ 2 = 24.37, P < 0.001), indicating that habitat characteristics were similar to those selected by the aerially surveyed elk. Our D 2 model indicated that the best elk habitat primarily occurred in northern and western Arkansas and was associated with areas of high landscape heterogeneity, heavy forest cover, gently sloping ridge tops and valleys, low human population density, and low road densities. To assess the potential for elk–human conflicts in Arkansas, we used the analytical hierarchy process to rank the importance of 8 criteria based on expert opinion from biologists involved in elk management. The biologists ranked availability of forage on public lands as having the strongest influence on the potential for elk–human conflict (33%), followed by human population growth rate (22%) and the amount of private land in row crops (18%). We then applied those rankings in a weighted linear summation to map the relative potential for elk–human conflict. Finally, we used white-tailed deer ( Odocoileus virginianus ) densities to identify areas where success of elk restoration may be hampered due to meningeal worm ( Parelaphostrongylus tenuis ) transmission. By combining results of the 3 spatial data layers (i.e., habitat model, elk–human conflict model, deer density), our model indicated that restoration sites located in west-central and north-central Arkansas were most favorable for reintroduction.

Arkansas↗

USGS2012

Paleomagnetism of the Late Triassic Hound Island Volcanics: Revisited

The collision and accretion of the Alexander terrane profoundly influenced the geologic history of Alaska and western Canada; however, the terrane's displacement history is only poorly constrained by sparse paleomagnetic studies. We studied the paleomagnetism of the Hound Island Volcanics in order to evaluate the location of the Alexander terrane in Late Triassic time. We collected 618 samples at 102 sites in and near the Keku Strait, Alaska, from the Late Triassic Hound Island Volcanics, the Permian Pybus Formation, and 23-Ma gabbroic intrusions. We found three components of magnetization in the Hound Island Volcanics. The high-temperature component (component A) resides in hematite and magnetite and was found only in highly oxidized lava flows in a geographically restricted area. We think it is primary, or acquired soon after eruption of the lavas, principally because the directions pass a fold test. The paleolatitude indicated by this component (19.2° ± 10.3°) is similar to those determined for various portions of Wrangellia, consistent with the geologic interpretation that the Alexander terrane was with the Wrangellia terrane in Late Triassic time. We found two overprint directions in the Hound Island Volcanics. Component B was acquired 23 m.y. ago due to intrusion of gabbroic dikes and sills. This interpretation is indicated by the similarity of upper-hemisphere directions in the Hound Island Volcanics to those in the gabbro. Component C, found in both the Hound Island Volcanics and the Permian Pybus Formation, is oriented northeast and down, fails a regional fold test, and was acquired after regional deformation around 90 to 100 Ma. This overprint direction yields a paleolatitude similar to, but slightly higher than, slightly older rocks from the Coast Plutonic Complex, suggesting that the Alexander terrane was displaced 17° in early Late Cretaceous time. The occurrence of these two separate overprinting events provides a satisfying explanation of the earlier puzzling results from the Hound Island Volcanics (Hillhouse and Grommé, 1980). Finally, great-circle analysis of the paleomagnetic data from the Pybus Formation suggests the Alexander terrane may have been in the northern hemisphere in Permian time.

Alaska↗

USGS2014

Evidence against a Pleistocene desert refugium in the Lower Colorado River Basin

Aim The absence of Sonoran Desert plants in late Pleistocene-aged packrat middens has led to speculation that they survived glacial episodes either in refugia as intact associations (Clementsian community concept) or in dry microsites within chaparral or woodland according to individualistic species responses (Gleasonian community concept). To test these hypotheses, we developed a midden record from one likely refugium in north-eastern Baja California, Mexico. We also measured stomatal guard cell size in fossil leaves to further evaluate site-level individualistic responses of Larrea tridentata (creosote bush) ploidy races to climatic changes, including monsoonal history, over the late Quaternary. Location Sierra Juárez, Lower Colorado River Basin, north-eastern Baja California, Mexico. Methods Packrat ( Neotoma ) middens were collected from <300 m elevation on the eastern piedmont of the Sierra Juárez. Plant macrofossils and pollen were analysed from 50 dated middens, including determination of Larrea tridentata ploidy races. Results Pleistocene middens dating back to >55,000 cal. yr BP contained a mix of extralocal species characteristic of chaparral and pinyon–juniper–oak woodland, along with some modern desert elements. Many other desert taxa were absent during the Pleistocene, although most had arrived by the beginning of the Holocene 11,700 years ago. Main conclusions The assemblage of chaparral, woodland and select desert elements refutes the hypothesis that the Lower Colorado River Basin served as a late Pleistocene refugium for Sonoran Desert flora. The rapid arrival of most missing desert species by the early Holocene suggests they did not have far to migrate. They probably survived the last glacial period as smaller, disparate populations in dry microsites within chaparral and pinyon–juniper–oak woodlands. Diploid and tetraploid races of Larrea tridentata were present during the Pleistocene, but hexaploids did not appear until the mid-Holocene. This demonstrates that individualistic responses to climate involved genetic variants, in this case cytotypes, and not just species.

Baja California↗

USGS2005

Cryopreservation of sperm of red abalone (Haliotis rufescens)

Abalone culture, a developing industry in Baja California, Mexico, would benefit from genetic improvement and controlled breeding. The use of cryopreserved sperm would allow germplasm availability, and this study was designed to develop sperm cryopreservation protocols for red abalone Haliotis rufescens . The acute toxic effects of the cryoprotectants dimethyl sulfoxide (DMSO), propylene glycol (PG), and glycerol (GLY) were assessed after suspending sperm in different concentrations, whereby cryoprotectant treatments of 10% DMSO and 10% GLY equilibrated for 10 min yielded the highest range of motile sperm in preliminary freezing trials and were used for cryopreservation studies. To determine effective cooling rates, three freezing chambers were tested. Replicate samples of sperm from 4 males were placed in 0.5-mL French straws and frozen using a commercial freezing chamber (CFC) used for bull sperm, a programmable rate chamber (PRC), and a manually controlled styrofoam chamber (MCC). For the CFC, the cooling rate was 16°C/min, from 4°C to −140°C. For the PRC and MCC, it was 1°C/min, from −20°C to −30°C. The samples were held at −30°C for 5 min before being plunged into liquid nitrogen (−196°C) for storage, and each sample was thawed in a water bath at 45°C for 8 s. The quality of thawed sperm was determined by estimating percent motility, evaluating membrane integrity using a dual-staining technique and flow cytometry, and estimating fertilization rate. Statistical analyses were performed using 2-way ANOVA where chamber and treatment were the independent variables. Sperm quality parameters were independent. For motilities, a significant interaction was noted between the cryoprotective treatment and the chamber type, whereby motilities for DMSO and GLY were higher ( P = 0.0055) using MCC. Membrane integrities were significantly lower after using the PRC than the CFC or the MCC ( P = 0.0167). The highest post-thaw motility (48 ± 7%) was found using sperm suspended in 10% glycerol and frozen in the MCC. The highest percent of intact membranes (56 ± 11%) was for sperm suspended in 10% glycerol and frozen in the CFC. The highest fertilization rate (29 ± 10%) was with samples frozen with 10% glycerol in the CFC. The use of cryopreserved sperm from red abalone provides an alternative breeding option for culture and the protocols delineated are the first developed for this species.

Baja California↗

USGS2019

Factors influencing nesting ecology of lesser prairie-chickens

Lesser prairie-chicken ( Tympanuchus pallidicinctus ) populations have declined since the 1980s. Understanding factors influencing nest-site selection and nest survival are important for conservation and management of lesser prairie-chicken populations. However, >75% of the extant population is in the northern extent of the range where data on breeding season ecology are lacking. We tested factors influencing fine-scale and regional nest-site selection and nest survival across the northern portion of the lesser prairie-chicken range. We trapped and affixed satellite global positioning system and very high frequency transmitters to female lesser prairie-chickens ( n = 307) in south-central and western Kansas and eastern Colorado, USA. We located and monitored 257 lesser prairie-chicken nests from 2013 to 2016. We evaluated nest-site selection and nest survival in comparison to vegetation composition and structure. Overall, nest-site selection in relation to vegetation characteristics was similar across our study area. Lesser prairie-chickens selected nest microsites with 75% visual obstruction 2.0–3.5 dm tall and 95.7% of all nests were in habitat with ≥1 dm and ≤4 dm visual obstruction. Nests were located in areas with 6–8% bare ground, on average, avoiding areas with greater percent cover of bare ground. The type of vegetation present was less important than cover of adequate height. Nest survival was maximized when 75% visual obstruction was 2.0–4.0 dm. Nest survival did not vary spatially or among years and generally increased as intensity of drought decreased throughout the study although not significantly. To provide nesting cover considering yearly variation in drought conditions, it is important to maintain residual cover by managing for structural heterogeneity of vegetation. Managing for structural heterogeneity could be accomplished by maintaining or strategically applying practices of the Conservation Reserve Program, using appropriate fire and grazing disturbances in native working grasslands, and establishing site-specific monitoring of vegetation composition and structure.

Colorado, Kansas↗