Stable Hydrogen Isotope Analysis of Bat Hair as Evidence for Seasonal Molt and Long-Distance Migration

Although hoary bats (Lasiurus cinereus) are presumed to be migratory and capable of long-distance dispersal, traditional marking techniques have failed to provide direct evidence of migratory movements by individuals. We measured the stable hydrogen isotope ratios of bat hair (∂Dh) and determined how these values relate to stable hydrogen isotope ratios of precipitation (∂Dp). Our results indicate that the major assumptions of stable isotope migration studies hold true for hoary bats and that the methodology provides a viable means of determining their migratory movements. We present evidence that a single annual molt occurs in L. cinereus prior to migration and that there is a strong relationship between ∂Dh and ∂Dp during the molt period. This presumably reflects the incorporation of local ∂Dp into newly grown hair. Furthermore, we present evidence that individual hoary bats are capable of traveling distances in excess of 2,000 km and that hair is grown at a wide range of latitudes and elevations. Stable hydrogen isotope analysis offers a promising new tool for the study of bat migration

Stable Hydrogen Isotope Analysis of Bat Hair as Evidence for Seasonal Molt and Long-Distance Migration

Although hoary bats (Lasiurus cinereus) are presumed to be migratory and capable of long-distance dispersal, traditional marking techniques have failed to provide direct evidence of migratory movements by individuals. We measured the stable hydrogen isotope ratios of bat hair (∂Dh) and determined how these values relate to stable hydrogen isotope ratios of precipitation (∂Dp). Our results indicate that the major assumptions of stable isotope migration studies hold true for hoary bats and that the methodology provides a viable means of determining their migratory movements. We present evidence that a single annual molt occurs in L. cinereus prior to migration and that there is a strong relationship between ∂Dh and ∂Dp during the molt period. This presumably reflects the incorporation of local ∂Dp into newly grown hair. Furthermore, we present evidence that individual hoary bats are capable of traveling distances in excess of 2,000 km and that hair is grown at a wide range of latitudes and elevations. Stable hydrogen isotope analysis offers a promising new tool for the study of bat migration

Holocene multidecadal and multicentennial droughts affecting Northern California and Nevada

Continuous, high-resolution δ18O records from cored sediments of Pyramid Lake, Nevada, indicate that oscillations in the hydrologic balance occurred, on average, about every 150 years (yr) during the past 7630 calendar years (cal yr). The records are not stationary; during the past 2740 yr, drought durations ranged from 20 to 100 yr and intervals between droughts ranged from 80 to 230 yr. Comparison of tree-ring-based reconstructions of climate change for the past 1200 yr from the Sierra Nevada and the El Malpais region of northwest New Mexico indicates that severe droughts associated with Anasazi withdrawal from Chaco Canyon at 820 cal yr BP (calendar years before present) and final abandonment of Chaco Canyon, Mesa Verde, and the Kayenta area at 650 cal yr BP may have impacted much of the western United States.During the middle Holocene (informally defined in this paper as extending from 8000 to 3000 cal yr BP), magnetic susceptibility values of sediments deposited in Pyramid Lake’s deep basin were much larger than late–Holocene (3000–0 cal yr BP) values, indicating the presence of a shallow lake. In addition, the mean δ18O value of CaCO3 precipitated between 6500 and 3430 cal yr BP was 1.6m less than the mean value of CaCO3 precipitated after 2740 cal yr BP. Numerical calculations indicate that the shift in the δ18O baseline probably resulted from a transition to a wetter (\u3e30%) and cooler (3–5 °C) climate. The existence of a relatively dry and warm middle-Holocene climate in the Truckee River– Pyramid Lake system is generally consistent with archeological, sedimentological, chemical, physical, and biological records from various sites within the Great Basin of the western United States. Two high-resolution Holocene-climate records are now available from the Pyramid and Owens lake basins which suggest that the Holocene was characterized by five climatic intervals. TIC and δ18O records from Owens Lake indicate that the first interval in the early Holocene (11,600–10,000 cal yr BP) was characterized by a drying trend that was interrupted by a brief (200 yr) wet oscillation centered at 10,300 cal yr BP. This was followed by a second early- Holocene interval (10,000–8000 cal yr BP) during which relatively wet conditions prevailed. During the early part of the middle Holocene (8000–6500 cal yr BP), high-amplitude oscillations in TIC in Owens Lake and d18O in Pyramid Lake indicate the presence of shallow lakes in both basins. During the latter part of the middle Holocene (6500–3800 cal yr BP), drought conditions dominated, Owens Lake desiccated, and Lake Tahoe ceased spilling to the Truckee River, causing Pyramid Lake to decline. At the beginning of the late Holocene (~3000 cal yr BP), Lake Tahoe rose to its sill level and Pyramid Lake increased in volume

Chapter 8: Meta-analysis of Test Performance When There is a “Gold Standard”

Synthesizing information on test performance metrics such as sensitivity, specificity, predictive values and likelihood ratios is often an important part of a systematic review of a medical test. Because many metrics of test performance are of interest, the meta-analysis of medical tests is more complex than the meta-analysis of interventions or associations. Sometimes, a helpful way to summarize medical test studies is to provide a “summary point”, a summary sensitivity and a summary specificity. Other times, when the sensitivity or specificity estimates vary widely or when the test threshold varies, it is more helpful to synthesize data using a “summary line” that describes how the average sensitivity changes with the average specificity. Choosing the most helpful summary is subjective, and in some cases both summaries provide meaningful and complementary information. Because sensitivity and specificity are not independent across studies, the meta-analysis of medical tests is fundamentaly a multivariate problem, and should be addressed with multivariate methods. More complex analyses are needed if studies report results at multiple thresholds for positive tests. At the same time, quantitative analyses are used to explore and explain any observed dissimilarity (heterogeneity) in the results of the examined studies. This can be performed in the context of proper (multivariate) meta-regressions

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Environmental Factors Affecting Mercury in Camp Far West Reservoir, California, 2001–03

This report documents water quality in Camp Far West Reservoir from October 2001 through August 2003. The reservoir, located at approximately 300 feet above sea level in the foothills of the northwestern Sierra Nevada, California, is a monomictic lake characterized by extreme drawdown in the late summer and fall. Thermal stratification in summer and fall is coupled with anoxic conditions in the hypolimnion. Water-quality sampling was done at approximately 3-month intervals on eight occasions at several stations in the reservoir, including a group of three stations along a flow path in the reservoir: an upstream station in the Bear River arm (principal tributary), a mid-reservoir station in the thalweg (pre-reservoir river channel), and a station in the deepest part of the reservoir, in the thalweg near Camp Far West Dam. Stations in other tributary arms of the reservoir included those in the Rock Creek arm of the reservoir, a relatively low-flow tributary, and the Dairy Farm arm, a small tributary that receives acidic, metal-rich drainage seasonally from the inactive Dairy Farm Mine, which produced copper, zinc, and gold from underground workings and a surface pit. Several water-quality constituents varied significantly by season at all sampling stations, including major cations and anions, total mercury (filtered and unfiltered samples), nitrogen (ammonia plus organic), and total phosphorus. A strong seasonal signal also was observed for the sulfur-isotope composition of aqueous sulfate from filtered water. Although there were some spatial differences in water quality, the seasonal variations were more profound. Concentrations of total mercury (filtered and unfiltered water) were highest during fall and winter; these concentrations decreased at most stations during spring and summer. Anoxic conditions developed in deep parts of the reservoir during summer and fall in association with thermal stratification. The highest concentrations of methylmercury in unfiltered water were observed in samples collected during summer from deep-water stations in the anoxic hypolimnion. In the shallow (less than 14 meters depth) oxic epilimnion, concentrations of methylmercury in unfiltered water were highest during the spring and lowest during the fall. The ratio of methylmercury to total mercury (MeHg/HgT) increased systematically from winter to spring to summer, largely in response to the progressive seasonal decrease in total mercury concentrations, but also to some extent because of increases in MeHg concentrations during summer. Water-quality data for Camp Far West Reservoir are used in conjunction with data from linked studies of sediment and biota to develop and refine a conceptual model for mercury methylation and bioaccumulation in the reservoir and the lower Bear River watershed. It is hypothesized that MeHg is produced by sulfate-reducing bacteria in the anoxic parts of the water column and in shallow bed sediment. Conditions were optimal for this process during late summer and fall. Previous work has indicated that Camp Far West Reservoir is a phosphate-limited system—molar ratios of inorganic nitrogen to inorganic phosphorus in filtered water were consistently greater than 16 (the Redfield ratio), sometimes by orders of magnitude. Therefore, concentrations of orthophosphate were expectedly very low or below detection at all stations during all seasons. It is further hypothesized that iron-reducing bacteria facilitate release of phosphorus from iron-rich sediments during summer and early fall, stimulating phytoplankton growth in the fall and winter, and that the MeHg produced in the hypolimnion and metalimnion is released to the entire water column in the late fall during reservoir destratification (vertical mixing). Mercury bioaccumulation factors (BAF) were computed using data from linked studies of biota spanning a range of trophic position: zooplankton, midge larvae, mayfly nymphs, crayfish, threadfin shad, bluegill, and spotted bass. Significant increases in total mercury in tissue with increasing organism size were observed for all three fish species and for crayfish. The BAF values were computed using the average methylmercury concentration (wet) in biota divided by the arithmetic mean concentration of methylmercury in filtered water (0.04 nanograms per liter). As expected, the BAF values increased systematically with increasing trophic position. Values of BAF were 190,000 for zooplankton; 470,000 to 930,000 for three taxa of invertebrates; 2.7 million for threadfin shad (whole body); 4.2 million for bluegill (fillet); and 10 million for spotted bass (fillet). The BAF values are high compared with those for biota in other reservoirs in northern California and elsewhere, indicating relatively efficient biomagnification of mercury in Camp Far West Reservoir

Applications of Trace-Element and Stable-Isotope Geochemistry to Wildlife Issues, Yellowstone National Park and Vicinity

Reconnaissance investigations have been conducted to identify how geochemical techniques can be applied to biological studies to assist wildlife management in and near Yellowstone National Park (the Park). Many elements (for example, As, B, Be, Ce, Cl, Cs, F, Hg, K, Li, Mo, Rb, S, Sb, Si, and W) are commonly enriched in (1) thermal waters in the Yellowstone area, (2) rocks altered by these waters, (3) sinter and travertine deposits, and (4) soils and stream sediments derived from these rocks. Some of these elements, such as As, F, Hg, and Mo, may be toxic to wildlife and could be passed up the food chain to many species of animals. Three investigations are described here. The first discusses the abundance and distribution of selected elements in the scat (feces) of bison (Bison bison), elk (Cervus elaphus), and moose (Alces alces) collected in and near the Park from areas underlain by both unaltered and hydrothermally altered rock. As compared to mean values for stream-sediment analyses, those of scat analyses collected in the Yellowstone area show relatively high concentrations for 12 elements. This suite of elements comprises (1) hydrothermally related elements (As, Br, Cs, Mo, Sb, and W), (2) essential major elements for plants (Ca and K) and some trace elements (Ba, Rb, and Sr) that commonly proxy (substitute) for Ca or K, and (3) zinc. The behavior of zinc is not understood. It is an essential element for plants and animals but does not normally proxy for either Ca or K. Zinc is also not related to hydrothermal activity. This unique behavior of zinc is discussed in other parts of this investigation. Six elements (Cr, Hg, Ni, Pb, Se, and U) that can be toxic to wildlife are present in low concentrations in scat, reflecting their generally low concentrations in rock and stream-sediment samples collected throughout the Park. The chemistry of large-animal scat provides information on the feeding habits of large animals in the Park. Scat chemistry shows a high spatial correlation with fossil or active thermal areas or with areas immediately downstream from thermal areas. The longer that animals forage in these localities, the more likely it is that they may ingest significant amounts of potentially toxic elements such as arsenic. A second investigation describes the concentration levels of hydrothermal mercury and other elements in cutthroat trout (Oncorhynchus clarki bouvieri) and lake trout (Salvelinus namaycush). These elements are derived from sublacustrine hot springs and their habitats in Yellowstone Lake, and this study demonstrates that mercury can be used as a tracer in animal ecology studies. Mercury concentrations are significant in the muscle (average 0.9 ppm, dry weight for both) and liver (average cutthroat = 1.6 ppm, dry weight; average lake trout = 2.1 ppm) of cutthroat and lake trout populations. The mercury levels in fish are believed to be related to mercury introduced to the lake by sublacustrine hot springs, which have dissolved mercury concentrations of as much as 0.170 ppb. Methylation of mercury in thermal waters is probably carried out by methanogenic or sulfate-reducing bacteria that live around sublacustrine hot springs and are consumed by crustaceans such as amphipods, which are a major food source for the cutthroat trout. The mercury levels in the cutthroat trout are transferred to lake trout and to land animals that eat trout. For example, hair of grizzly bears that have been collected near Yellowstone Lake have high mercury levels (0.6–1.7 ppm, dry weight), whereas hair of bears sampled at more remote areas in the greater Yellowstone ecosystem have low mercury contents (0.006–0.09 ppm, dry weight). This observation provides strong evidence that mercury in grizzly bears is derived from feeding on spawning cutthroat trout in the spring and early summer. Studies of mercury and metal contents in other grizzly bear food sources (plants and animals) show that only cutthroat trout are strongly enriched in mercury. These data can potentially be used to quantify the percentage of the bear population that eats cutthroat trout and to determine how far individual bears travel to Yellowstone Lake to eat them. A third investigation describes carbon-, nitrogen-, and sulfur-isotope compositions in grizzly bears and in some of their foods and describes how these data can be applied to studies of grizzly bear demographics. δ13C values in the Yellowstone ecosystem range from –21.7 ‰ to –30.4 ‰, a range that reflects the influence of C3 plants on the carbon reservoir and probably the effect of elevation on physiological processes. δ15N values range from –2.3 ‰ to 11.0 ‰ and show classical trophic enrichments with respect to most grizzly bear food sources. Cutthroat trout δ15N values (8.3±1.0 ‰) may reflect the importance of sublacustrine hydrothermal springs to the food chain in Yellowstone Lake. Lake trout have even larger δ15N values (11.0±0.4 ‰) that are consistent with their feeding on cutthroat trout. Grizzly bear δ15N values range from 7.0 ‰ to 8.8 ‰. Although grizzly bears are known to eat cutthroat trout, trophic enrichment in δ15N above values found in trout is not apparent in analyses of bear hair. This discrepancy occurs because δ15N values are averaged over one year and include the significantly lower δ15N values of vegetable food sources consumed by bears while their hair is growing. δ34S values in the ecosystem range from –3.1 ‰ to 11.1 ‰. δ34S values of fish (1.2±0.5 ‰) are nearly the same as those in sulfate from thermal springs. Vegetation (clover, cow parsnip, and spring beauty), ungulates (deer, elk, and bison), and moths show a greater range of δ34S values (–3.3 ‰ to 3.2 ‰). However, bears show higher δ34S values (3.2 ‰ to 5.4 ‰ in muscle and 6.1 ‰ to 8.7 ‰ in hair) that are consistent with the consumption of whitebark pine nuts (δ34S = 8.3 ‰ to 11.4 ‰). δ34S values in bears and their food sources seem to be constrained by the major sources of sulfate and sulfide sulfur in the igneous and sedimentary rocks that underlie much of the Park. The large δ34S values found in bear tissues are consistent with the documented fact that most grizzly bears eat substantial amounts of whitebark pine nuts when available. This consumption occurs during hair growth in the fall, thus providing an isotopic marker that may be useful in quantifying nut consumption in individual bears. These three studies show some different ways that geochemical techniques can be applied to biologic issues. The results suggest that integration of geochemistry into specific biologic studies may help address issues of interest to wildlife managers in Yellowstone National Park and the greater Yellowstone ecosystem