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At least 1,081 records · Page 60Linked to original sources

USGS2010

Spatial and stage-structured population model of the American crocodile for comparison of comprehensive Everglades Restoration Plan (CERP) alternatives

As part of the U.S. Geological Survey Priority Ecosystems Science (PES) initiative to provide the ecological science required during Everglades restoration, we have integrated current regional hydrologic models with American crocodile (Crocodylus acutus) research and monitoring data to create a model that assesses the potential impact of Comprehensive Everglades Restoration Plan (CERP) efforts on the American crocodile. A list of indicators was created by the Restoration Coordination and Verification (RECOVER) component of CERP to help determine the success of interim restoration goals. The American crocodile was established as an indicator of the ecological condition of mangrove estuaries due to its reliance upon estuarine environments characterized by low salinity and adequate freshwater inflow. To gain a better understanding of the potential impact of CERP restoration efforts on the American crocodile, a spatially explicit crocodile population model has been created that has the ability to simulate the response of crocodiles to various management strategies for the South Florida ecosystem. The crocodile model uses output from the Tides and Inflows in the Mangroves of the Everglades (TIME) model, an application of the Flow and Transport in a Linked Overland/Aquifer Density Dependent System (FTLOADDS) simulator. TIME has the capability to link to the South Florida Water Management Model (SFWMM), which is the primary regional tool used to assess CERP restoration scenarios. A crocodile habitat suitability index and spatial parameter maps that reflect salinity, water depth, habitat, and nesting locations are used as driving functions to construct crocodile finite rate of increase maps under different management scenarios. Local stage-structured models are integrated with a spatial landscape grid to display crocodile movement behavior in response to changing environmental conditions. Restoration efforts are expected to affect salinity levels throughout the habitat of the American crocodile. This modeling effort examines how CERP restoration alternatives will affect growth and survival rates of hatchling and juvenile crocodiles, hatchling dispersal to suitable nursery habitat, and relative abundance and distribution in response to changing salinity and water depth for all stage classes of crocodiles. The response of the American crocodile to restoration efforts will provide a quantifiable measure of restoration success. By applying the crocodile model to proposed restoration alternatives and predicting population responses, we can choose alternatives that approximate historical conditions, enhance habitat for multiple species, and identify future research needs.

Open-File Report↗

USGS2020

Eradication of peste des petits ruminants and the wildlife-livestock interface

Growing evidence suggests that multiple wildlife species can be infected with peste des petits ruminants virus (PPRV), with important consequences for the potential maintenance of PPRV in communities of susceptible hosts, and the threat that PPRV may pose to the conservation of wildlife populations and resilience of ecosystems. Significant knowledge gaps in the epidemiology of PPRV across the ruminant community (wildlife and domestic), and the understanding of infection in wildlife and other atypical host species groups (e.g., camelidae, suidae, and bovinae) hinder our ability to apply necessary integrated disease control and management interventions at the wildlife-livestock interface. Similarly, knowledge gaps limit the inclusion of wildlife in the FAO/OIE Global Strategy for the Control and Eradication of PPR, and the framework of activities in the PPR Global Eradication Programme that lays the foundation for eradicating PPR through national and regional efforts. This article reports on the first international meeting on, “Controlling PPR at the livestock-wildlife interface,” held in Rome, Italy, March 27–29, 2019. A large group representing national and international institutions discussed recent advances in our understanding of PPRV in wildlife, identified knowledge gaps and research priorities, and formulated recommendations. The need for a better understanding of PPRV epidemiology at the wildlife-livestock interface to support the integration of wildlife into PPR eradication efforts was highlighted by meeting participants along with the reminder that PPR eradication and wildlife conservation need not be viewed as competing priorities, but instead constitute two requisites of healthy socio-ecological systems.

Frontiers in Veterinary Science↗

USGS2004

Mars chronology: Assessing techniques for quantifying surficial processes

Currently, the absolute chronology of Martian rocks, deposits and events is based mainly on crater counting and remains highly imprecise with epoch boundary uncertainties in excess of 2 billion years. Answers to key questions concerning the comparative origin and evolution of Mars and Earth will not be forthcoming without a rigid Martian chronology, enabling the construction of a time scale comparable to Earth's. Priorities for exploration include calibration of the cratering rate, dating major volcanic and fluvial events and establishing chronology of the polar layered deposits. If extinct and/or extant life is discovered, the chronology of the biosphere will be of paramount importance. Many radiometric and cosmogenic techniques applicable on Earth and the Moon will apply to Mars after certain baselines (e.g. composition of the atmosphere, trace species, chemical and physical characteristics of Martian dust) are established. The high radiation regime may pose a problem for dosimetry-based techniques (e.g. luminescence). The unique isotopic composition of nitrogen in the Martian atmosphere may permit a Mars-specific chronometer for tracing the time-evolution of the atmosphere and of lithic phases with trapped atmospheric gases. Other Mars-specific chronometers include measurement of gas fluxes and accumulation of platinum group elements (PGE) in the regolith. Putting collected samples into geologic context is deemed essential, as is using multiple techniques on multiple samples. If in situ measurements are restricted to a single technique it must be shown to give consistent results on multiple samples, but in all cases, using two or more techniques (e.g. on the same lander) will reduce error. While there is no question that returned samples will yield the best ages, in situ techniques have the potential to be flown on multiple missions providing a larger data set and broader context in which to place the more accurate dates. ?? 2004 Elsevier B.V. All rights reserved.

Earth-Science Reviews↗

USGS2012

Steroid hormone runoff from agricultural test plots applied with municipal biosolids

The potential presence of steroid hormones in runoff from sites where biosolids have been used as agricultural fertilizers is an environmental concern. A study was conducted to assess the potential for runoff of seventeen different hormones and two sterols, including androgens, estrogens, and progestogens from agricultural test plots. The field containing the test plots had been applied with biosolids for the first time immediately prior to this study. Target compounds were isolated by solid-phase extraction (water samples) and pressurized solvent extraction (solid samples), derivatized, and analyzed by gas chromatography–tandem mass spectrometry. Runoff samples collected prior to biosolids application had low concentrations of two hormones (estrone <0.8 to 2.23 ng L -1 and androstenedione <0.8 to 1.54 ng L -1 ) and cholesterol (22.5 ± 3.8 μg L -1 ). In contrast, significantly higher concentrations of multiple estrogens (<0.8 to 25.0 ng L -1 ), androgens (<2 to 216 ng L -1 ), and progesterone (<8 to 98.9 ng L -1 ) were observed in runoff samples taken 1, 8, and 35 days after biosolids application. A significant positive correlation was observed between antecedent rainfall amount and hormone mass loads (runoff). Hormones in runoff were primarily present in the dissolved phase (<0.7-μm GF filter), and, to a lesser extent bound to the suspended-particle phase. Overall, these results indicate that rainfall can mobilize hormones from biosolids-amended agricultural fields, directly to surface waters or redistributed to terrestrial sites away from the point of application via runoff. Although concentrations decrease over time, 35 days is insufficient for complete degradation of hormones in soil at this site.

Environmental Science & Technology↗

USGS2014

Variation in the terrestrial isotopic composition and atomic weight of argon

The isotopic composition and atomic weight of argon (Ar) are variable in terrestrial materials. Those variations are a source of uncertainty in the assignment of standard properties for Ar, but they provide useful information in many areas of science. Variations in the stable isotopic composition and atomic weight of Ar are caused by several different processes, including (1) isotope production from other elements by radioactive decay (radiogenic isotopes) or other nuclear transformations (e.g., nucleogenic isotopes), and (2) isotopic fractionation by physical-chemical processes such as diffusion or phase equilibria. Physical-chemical processes cause correlated mass-dependent variations in the Ar isotope-amount ratios ( 40 Ar/ 36 Ar, 38 Ar/ 36 Ar), whereas nuclear transformation processes cause non-mass-dependent variations. While atmospheric Ar can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other Ar occurrences limit the precision with which a standard atomic weight can be given for Ar. Published data indicate variation of Ar atomic weights in normal terrestrial materials between about 39.7931 and 39.9624. The upper bound of this interval is given by the atomic mass of 40 Ar, as some samples contain almost pure radiogenic 40 Ar. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36 Ar and 38 Ar. Within this interval, measurements of different isotope ratios ( 40 Ar/ 36 Ar or 38 Ar/ 36 Ar) at various levels of precision are widely used for studies in geochronology, water–rock interaction, atmospheric evolution, and other fields.

Pure and Applied Chemistry↗

USGS1969

Dilemma posed by uranium-series dates on archaeologically significant bones from Valsequillo, Puebla, Mexico

In an attempt to date stone artifacts of Early Man excavated from several sites at the Valsequillo Reservoir, a few kilometers south of Puebla, Mexico, Szabo applied the uranium-series method on bone samples known to be either from the same geologic formation as the sites or in direct association with the artifacts. The geologic context of the bones was studied by Malde, and the archaeological sites were excavated by Irwin-Williams. A date determined for bone associated with an artifact (Caulapan sample M-B-6, see below) agrees with a radiocarbon date for fossil mollusks in the same bed and indicates man's presence more than 20 000 years ago. However, some of these bone dates exceed 200 000 years. Because such dates for man in North America conflict with all prior archaeological evidence here and abroad, we are confronted by a dilemna — either to defend the dates against an onslaught of archaeological thought, or to abandon the uranium method in this application as being so much wasted effort. Faced with these equally undesirable alternatives, and unable to decide where the onus fairly lies (if a choice must be made), we give the uranium-series dates as a possible stimulus for further mutual work in isotopic dating of archaeological material. A sample from the Lindenmeier archaeological site north of Fort Collins and another from a Pleistocene terrace along the Arkansas River, both in Colorado, were also dated.

Puebla↗

USGS2008

Sexual maturation in kokanee Oncorhynchus nerka

We used observational and experimental approaches to obtain information on factors affecting the timing of maturation of kokanee Oncorhynchus nerka, a semelparous, landlocked salmon. Gonadal staging criteria were developed and applied to three kokanee populations in Idaho lakes and reservoirs. Testes were classified into three stages: immature (stage one, S1), maturing (S2), and mature (S3). Ovaries were classified into eight stages: immature (S1-S3), transitional (stage S4), maturing (S5-S7), and mature (S8). Males entered the maturing stage (S2) in February through April of the spawning year. Females entered maturing stage (S5) as early as July of the year before the spawning year, and as late as March of the spawning year. Three hatchery experiments demonstrated that attainment of a larger body size 10 to 16 months before spawning increased the likelihood of initiation of maturation in both sexes. No gonads in a state of regression were observed. A gonadosomatic index above 0.1 by early July was a good indicator of a maturing male, and a gonadosomatic index above 1.0 by early July was a good indicator of a maturing female. Instantaneous growth rates were not good predictors of maturation, but attaining a size threshold of 18 to 19 cm in the fall was a good predictor of maturation the following year. This improved knowledge of kokanee maturation will permit more effectively management of the species for age, growth and size at maturity as well as for contributions to fisheries. ?? 2008 by the Northwest Scientific Association. All rights reserved.

Northwest Science↗

USGS2020

Using the Lomb-Scargle method for wave statistics from gappy time series

Sandwich Town Neck Beach in Sandwich, MA, has experienced substantial erosion and has been the subject of efforts by the town and private landowners to limit the sand loss. Erosion has been particularly dramatic in the past five years with the loss of dwellings. Sandwich's nourishment efforts presented a unique opportunity for scientists at the U.S. Geological Survey Woods Hole Coastal and Marine Science Center to monitor beach morphology and to test new technologies and techniques such as geo-referenced drone imaging. Two bottom lander deployments were performed in Cape Cod Bay at a location that was key to model the fate of waves at Sandwich Town Neck Beach and to support the study of beach morphological evolution. The study period was after the town nourished the beach and during a time when several intense winter storms reshaped the beach and removed much of the nourished sand. A TRDI Workhorse Sentinel V ADCP was used for both deployments. For wave bursts, the instruments collected 2048 samples at 2 Hz every hour. The first deployment during the winter of 2016 returned good quality data. The second deployment during the following winter had gaps throughout the time series from a wiring problem in the external battery pack. The timing of the gaps was random, the duration approximately 100 s. While most of the bursts started at the top of each hour, many had 1-3 gaps within. Time series data with random gaps are problematic for computing spectral density, and thus, wave statistics. This kind of situation is familiar in other scientific disciplines such as astrophysics [1], where techniques exist to find stationary signals in sparse data. One of these methods is the Lomb-Scargle technique for computing periodograms. The most useful feature of the Lomb-Scargle (LS) method is that it allows the spectral analysis of incomplete records, without having to manipulate the record to extrapolate from or replace missing data. We compared the effectiveness of LS against common methods of averaging Fourier transforms such as a simple un-windowed Fast Fourier transform (FFT), Welch's method, and TRDI's Wavesmon software; methods that are commonly used in oceanography for non-gappy data. Synthetic data series that have been artificially modified to introduce gaps were used to evaluate the performance of each method. The LS approach was able to recover spectral density even with several 100-s gaps present. The method was applied here to the gappy and non-gappy data from both Sandwich deployments, and wave statistics were obtained and compared to the wave-buoy data. LS was used to process data that contains gaps that was rejected by Wavesmon, which was approximately 39% of the dataset. Significant wave height and peak period from LS compared well with buoy data. Mean period computed on gappy data using LS produced values biased low, compared with other methods when gaps were filled with the mean value. The LS technique has potential to uncover low-frequency signals such as infragravity waves from gappy records where the non-gappy segments are not long enough to resolve them. It has potential to unlock new information from older data sets.

Massachusetts↗

USGS2017

3D Pressure‐limited approach to model and estimate CO2 injection and storage capacity: saline Mount Simon Formation

To estimate the carbon dioxide (CO 2 ) injection and storage capacity of saline formations, we used Tough2‐ECO2N simulation software to develop a pressure‐limited (dynamic) simulation approach based on applying three‐dimensional (3D) numerical simulation only on the effective injection area (A eff ) surrounding each injection well. A statistical analysis was performed to account for existing reservoir heterogeneity and property variations. The accuracy of the model simulation results (such as CO 2 plume extension and induced injection well bottomhole pressure values) were tested and verified against the data obtained from the Decatur CO 2 injection study of the Mount Simon Formation. Next, we designed a full‐field CO 2 injection pattern by populating the core sections of this formation with a series of the simulated effective injection areas such that each simulated A eff acts as a closed domain. The results of this analysis were used to estimate the optimum number and location of the required CO 2 injection wells, along with the dynamic annual CO 2 injection rate and overall pressure‐limited storage capacity of this formation. This approach enabled us to model separate CO 2 injection activities independently at different sections of the same saline formation and to model and simulate faults and natural barriers by considering them as boundary conditions for each simulated A eff without constructing full‐field models. Using this approach, a series of modeled A eff with relevant properties may be redesigned to model any other saline formation with a similar structure.

Mount Simon Formation↗

USGS2018

Chesapeake Bay's water quality condition has been recovering: Insights from a multimetric indicator assessment of thirty years of tidal monitoring data

To protect the aquatic living resources of Chesapeake Bay, the Chesapeake Bay Program partnership has developed guidance for state water quality standards, which include ambient water quality criteria to protect designated uses (DUs), and associated assessment procedures for dissolved oxygen (DO), water clarity/underwater bay grasses, and chlorophyll-a. For measuring progress toward meeting the respective states' water quality standards, a multimetric attainment indicator approach was developed to estimate combined standards attainment. We applied this approach to three decades of monitoring data of DO, water clarity/underwater bay grasses, and chlorophyll-a data on annually updated moving 3-year periods to track the progress in all 92 management segments of tidal waters in Chesapeake Bay. In 2014–2016, 40% of tidal water segment-DU-criterion combinations in the Bay (n = 291) are estimated to meet thresholds for attainment of their water quality criteria. This index score marks the best 3-year status in the entire record. Since 1985–1987, the indicator has followed a nonlinear trajectory, consistent with impacts from extreme weather events and subsequent recoveries. Over the period of record (1985–2016), the indicator exhibited a positive and statistically significant trend ( p < 0.05), indicating that the Bay has been recovering since 1985. Patterns of attainment of individual DUs are variable, but improvements in open water DO, deep channel DO, and water clarity/submerged aquatic vegetation have combined to drive the improvement in the Baywide indicator in 2014–2016 relative to its long-term median. Finally, the improvement in estimated Baywide attainment was statistically linked to the decline of total nitrogen, indicating responsiveness of attainment status to the reduction of nutrient load through various management actions since at least the 1980s.

Chesapeake Bay watershed↗

USGS2000

Volcano geodesy: Challenges and opportunities for the 21st century

Intrusions of magma beneath volcanoes deform the surrounding rock and, if the intrusion is large enough, the overlying ground surface. Numerical models generally agree that, for most eruptions, subsurface volume changes are sufficient to produce measurable deformation at the surface. Studying this deformation can help to determine the location, volume, and shape of a subsurface magma body and thus to anticipate the onset and course of an eruption. This approach has been successfully applied at many restless volcanoes, especially basaltic shields and silicic calderas, using various geodetic techniques and sensors. However, its success at many intermediate-composition strato-volcanoes has been limited by generally long repose intervals, steep terrain, and structural influences that complicate the history and shape of surface deformation. These factors have made it difficult to adequately characterize deformation in space and time at many of the world's dangerous volcanoes. Recent technological advances promise to make this task easier by enabling the acquisition of geodetic data of high spatial and temporal resolution from Earth-orbiting satellites. Synthetic aperture radar interferometry (InSAR) can image ground deformation over large areas at metre-scale resolution over time-scales of a month to a few years. Global Positioning System (GPS) stations can provide continuous information on three-dimensional ground displacements at a network of key sites -information that is especially important during volcanic crises. By using InSAR to determine the shape of the displacement field and GPS to monitor temporal changes at key sites, scientists have a much better chance to capture geodetic signals that have so far been elusive at many volcanoes. This approach has the potential to provide longer-term warnings of impending volcanic activity than is possible with other monitoring techniques.

Philosophical Transactions of the Royal Society A:↗

USGS2011

Excess nitrogen in the U.S. environment: Trends, risks, and solutions

It is not surprising that humans have profoundly altered the global nitrogen (N) cycle in an effort to feed 7 billion people, because nitrogen is an essential plant and animal nutrient. Food and energy production from agriculture, combined with industrial and energy sources, have more than doubled the amount of reactive nitrogen circulating annually on land. Humanity has disrupted the nitrogen cycle even more than the carbon (C) cycle. We present new research results showing widespread effects on ecosystems, biodiversity, human health, and climate, suggesting that in spite of decades of research quantifying the negative consequences of too much available nitrogen in the biosphere, solutions remain elusive. There have been important successes in reducing nitrogen emissions to the atmosphere and this has improved air quality. Effective solutions for reducing nitrogen losses from agriculture have also been identified, although political and economic impediments to their adoption remain. Here, we focus on the major sources of reactive nitrogen for the United States (U.S.), their impacts, and potential mitigation options. Sources: ??? Intensive development of agriculture, industry, and transportation has profoundly altered the U.S. nitrogen cycle. ??? Nitrogen emissions from the energy and transportation sectors are declining, but agricultural emissions are increasing. ??? Approximately half of all nitrogen applied to boost agricultural production escapes its intended use and is lost to the environment. Impacts: ??? Two-thirds of U.S. coastal systems are moderately to severely impaired due to nutrient loading; there are now approximately 300 hypoxic (low oxygen) zones along the U.S. coastline and the number is growing. One third of U.S. streams and two fifths of U.S. lakes are impaired by high nitrogen concentrations. ??? Air pollution continues to reduce biodiversity. A nation-wide assessment has documented losses of nitrogen-sensitive native species in favor of exotic, invasive species. ??? More than 1.5 million Americans drink well water contaminated with too much (or close to too much) nitrate (a regulated drinking water pollutant), potentially placing them at increased risk of birth defects and cancer. More research is needed to deepen understanding of these health risks. ??? Several pathogenic infections, including coral diseases, bird die-offs, fish diseases, and human diarrheal diseases and vector-borne infections are associated with nutrient losses from agriculture and from sewage entering ecosystems. ??? Nitrogen is intimately linked with the carbon cycle and has both warming and cooling effects on the climate. Mitigation Options: ??? Regulation of nitrogen oxide (NOX) emissions from energy and transportation sectors has greatly improved air quality, especially in the eastern U.S. Nitrogen oxide is expected to decline further as stronger regulations take effect, but ammonia remains mostly unregulated and is expected to increase unless better controls on ammonia emissions from livestock operations are implemented. ??? Nitrogen loss from farm and livestock operations can be reduced 30-50% using current practices and technologies and up to 70-90% with innovative applications of existing methods. Current U.S. agricultural policies and support systems, as well as declining investments in agricultural extension, impede the adoption of these practices. Society faces profound challenges to meet demands for food, fiber, and fuel while minimizing unintended environmental and human health impacts. While our ability to quantify transfers of nitrogen across land, water, and air has improved since the first publication of this series in 1997, an even bigger challenge remains: using the science for effective management policies that reduce climate change, improve water quality, and protect human and environmental health. ?? The Ecological Society of America.

Issues in Ecology↗

USGS2017

Comparison of in vitro estrogenic activity and estrogen concentrations insource and treated waters from 25 U.S. drinking water treatment plants

In vitro bioassays have been successfully used to screen for estrogenic activity in wastewater and surface water, however, few have been applied to treated drinking water. Here, extracts of source and treated water samples were assayed for estrogenic activity using T47D-KBluc cells and analyzed by liquid chromatography-Fourier transform mass spectrometry (LC-FTMS) for natural and synthetic estrogens (including estrone, 17β-estradiol, estriol, and ethinyl estradiol). None of the estrogenswere detected above the LC-FTMS quantification limits in treated samples and only 5 source waters had quantifiable concentrations of estrone, whereas 3 treated samples and 16 source samples displayed in vitro estrogenicity. Estrone accounted for themajority of estrogenic activity in respective samples, however the remaining samples that displayed estrogenic activity had no quantitative detections of known estrogenic compounds by chemical analyses. Source water estrogenicity (max, 0.47 ng 17β-estradiol equivalents (E2Eq) L−1) was below levels that have been linked to adverse effects in fish and other aquatic organisms. Treated water estrogenicity (max, 0.078 ng E2Eq L−1) was considerably below levels that are expected to be biologically relevant to human consumers. Overall, the advantage of using in vitro techniques in addition to analytical chemical determinations was displayed by the sensitivity of the T47D-KBluc bioassay, coupled with the ability tomeasure cumulative effects of mixtures, specifically when unknown chemicals may be present.

Science of the Total Environment↗

USGS2024

Seasonally varying contributions of contemporaneous and lagged sources of instream total nitrogen and phosphorus load across the Illinois River basin

Quantifying nutrient sources in streams, their temporal and spatial variability, and drivers of that variability can support effective water resources management. Yet a lack of data and modeling capabilities has previously prevented comprehensive quantification across both space and time. Here a dynamic SPARROW (Spatially Referenced Regressions on Watershed attributes) model that accounts for a lagged delivery of nutrients to streams was developed and applied to simulate seasonal and source-specific total nitrogen (TN) and total phosphorus (TP) loads in streams across the Illinois River basin (IRB). Dynamic load predictions from 2000 through 2020 revealed that a third of the TN and a quarter of the TP instream load originated from non-point sources that were lagged in their delivery from land-application to streams by more than a season. This lagged mass was the largest overall TN source—which was estimated as a lagged expression of previous seasonal non-point sources including fertilizer, manure, atmospheric deposition and fixation, and urban land use. Treated wastewater effluent was the largest TP source exported from the basin, contributing 39 % of the TP load and 15 % of the TN load, and dominated the load in the upper Illinois River near Chicago. Loads in the lower river during this period, conversely, were attributed primarily to a mix of agricultural sources and their lagged fractions from headwater tributaries. Instream processes removed 10 % of the TN load while only 4 % of the TP load was removed during instream transport. With appropriate datasets, the models could be extended to other basins or time periods and used to forecast future seasonal nutrient loads.

Illinois↗

USGS2018

Environmental conditions synchronize waterbird mortality events in the Great Lakes

Since the 1960s, periodic outbreaks of avian botulism type E have contributed to large-scale die-offs of thousands of waterbirds throughout the Great Lakes of the United States. In recent years, these events have become more common and widespread. Occurring during the summer and autumn months, the prevalence of these die-offs varies across years and is often associated with years of warmer lake temperatures and lower water levels. Little information exists on how environmental conditions mediate the spatial and temporal characteristics of mortality events. In 2010, a citizen science programme, Avian Monitoring for Botulism Lakeshore Events (AMBLE), was launched to enhance surveillance efforts and detect the appearance of beached waterbird carcasses associated with avian botulism type E outbreaks in northern Lake Michigan. Using these data, our goal was to quantify the within-year characteristics of mortality events for multiple species, and to test whether the synchrony of these events corresponded to fluctuations in two environmental factors suspected to be important in the spread of avian botulism: water temperature and the prevalence of green macroalgae. During two separate events of mass waterbird mortality, we found that the detection of bird carcasses was spatially synchronized at scales of c . 40 km. Notably, the extent of this spatial synchrony in avian mortality matched that of fluctuations in lake surface water temperatures and the prevalence of green macroalgae. Synthesis and applications . Our findings are suggestive of a synchronizing effect where warmer lake temperatures and the appearance of macroalgae mediate the characteristics of avian mortality. In future years, rising lake temperatures and a higher propensity of algal masses could lead to increases in the magnitude and synchronization of avian mortality due to botulism. We advocate that citizen-based monitoring efforts are critical for identifying the potential environmental conditions associated with widespread mortality events and estimating future risk to waterbird populations.

Journal of Applied Ecology↗

USGS2005

Designing occupancy studies: General advice and allocating survey effort

1. The fraction of sampling units in a landscape where a target species is present (occu pancy) is an extensively used concept in ecology. Yet in many applications the species will not always be detected in a sampling unit even when present, resulting in biased estimates of occupancy. Given that sampling units are surveyed repeatedly within a r elatively short timeframe, a number of similar methods have now been developed to provide unbiased occupancy estimates. However, practical guidance on the efficient design of occupancy studies has been lacking. 2. In this paper we comment on a number of general issues related to designing occu pancy studies, including the need for clear objectives that are explicitly linked to science or management, selection of sampling units, timing of repeat surveys and allocation of survey effort. Advice on the number of repeat surveys per sampling unit is considered in terms of the variance of the occupancy estimator, for three possible study designs. 3. We r ecommend that sampling units should be surveyed a minimum of three times w hen detection probability is high (> 0·5 survey − 1 ), unless a removal design is used. 4. We f ound that an optimal removal design will generally be the most efficient, but we suggest it may be less robust to assumption violations than a standard design. 5. Our results suggest that for a rare species it is more efficient to survey more sampling units less intensively, while for a common species fewer sampling units should be surveyed more intensively. 6. Synthesis and applications . Reliable inferences can only result from quality data. To ma ke the best use of logistical resources, study objectives must be clearly defined; sampling units must be selected, and repeated surveys timed appropriately; and a sufficient n umber of repeated surveys must be conducted. Failure to do so may compromise the integrity of the study. The guidance given here on study design issues is particularly a pplicable to studies of species occurrence and distribution, habitat selection and modelling, metapopulation studies and monitoring programmes.

Journal of Applied Ecology↗

USGS2020

Incorporating established conservation networks into freshwater conservation planning results in more workable prioritizations

Resources for addressing stream fish conservation issues are often limited and the stressors impacting fish continue to increase, so decision makers often rely on tools to prioritize locations for conservation actions. Because conservation networks already exist in many areas, incorporating these into the planning process can increase the ability of decision makers to carry out management actions. In this study we aim to identify priority areas within established networks to provide an approach which allows managers to focus efforts on the most valuable areas they control, while identifying areas outside of the network, which support species with minimal representation within the network, for acquisition or conservation partnerships. The goal of this approach is to prioritize sites to achieve high levels of species representation while also developing workable solutions. We applied a methodology incorporating established networks into a systematic conservation planning process for fish in temperate wadeable streams located in Missouri, USA. We compared how well species were represented in our approach with two commonly used alternatives: A blank slate approach which used the same systematic conservation planning technique but did not incorporate established networks, and a habitat integrity approach based solely on anthropogenic threat data. Relative to the blank slate approach, our approach required 210% more segments for representation of all species, and contained an average of 0.5 additional occurrences for the least well-represented species. Although the blank slate solution was more efficient in achieving species representation, 77% of segments in this solution were not already protected. This would likely pose a challenge for implementing conservation actions. Relative to habitat integrity-based priorities, our approach required only 38% of the number of stream segments to achieve representation of all species and contained an average of 5 additional occurrences of the least represented species, representing a substantial gain in representation. Incorporating established networks may allow managers to focus resources on areas with the greatest conservation value within established networks and to identify the most valuable areas complementary to the established networks, resulting in priorities which may be more actionable and effective than those developed by alternative approaches.

Missouri↗

USGS2022

Using active source seismology to image the Palos Verdes Fault damage zone as a function of distance, depth, and geology

Fault damage zones provide a window into the non-elastic processes of an earthquake. Geological and seismic tomography methods have been unable to measure damage zones at depth with sufficient spatial sampling to evaluate the relative influence of depth, distance, and lithological variations. Here, we identify and analyze the damage zone of the Palos Verdes Fault offshore southern California using two 3D seismic reflection datasets. We apply a novel algorithm to identify discontinuities attributed to faults and fractures in large seismic volumes and examine the spatial distribution of fault damage in sedimentary rock surrounding the Palos Verdes Fault. Our results show that damage through fracturing is most concentrated around mapped faults and decays exponentially to a distance of ∼2 km, where fracturing reaches a clearly defined and relatively undamaged background for all examined depths and lithologies (450 m to 2.2 km). This decrease in fracturing with distance from the central fault strand exhibits similar functional form to outcrop studies. However, here we extend analysis to distances seldom accessible (∼10 km lateral distance). Separating the data by geologic units we find that the damage decay and background level differs for each unit, with the older and deeper units having higher levels of background fracturing and shallower exponential decays of fracturing with distance from the fault. Surprisingly, these differences in damage decay and background level trade-off result in a consistent damage zone width regardless of lithology or depth. We find that the damage zone has similar decay trends on both sides of the fault. When examining the damage zone at shorter (4 km vs 17 km) along strike distances, the damage zone has a more complex decay trend and at least two strands are resolvable.

California↗