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At least 379 records · Page 21Linked to original sources
USGS2009

Modeling Flood Plain Hydrology and Forest Productivity of Congaree Swamp, South Carolina

An ecological field and modeling study was conducted to examine the flood relations of backswamp forests and park trails of the flood plain portion of Congaree National Park, S.C. Continuous water level gages were distributed across the length and width of the flood plain portion - referred to as 'Congaree Swamp' - to facilitate understanding of the lag and peak flood coupling with stage of the Congaree River. A severe and prolonged drought at study start in 2001 extended into late 2002 before backswamp zones circulated floodwaters. Water levels were monitored at 10 gaging stations over a 4-year period from 2002 to 2006. Historical water level stage and discharge data from the Congaree River were digitized from published sources and U.S. Geological Survey (USGS) archives to obtain long-term daily averages for an upstream gage at Columbia, S.C., dating back to 1892. Elevation of ground surface was surveyed for all park trails, water level gages, and additional circuits of roads and boundaries. Rectified elevation data were interpolated into a digital elevation model of the park trail system. Regression models were applied to establish time lags and stage relations between gages at Columbia, S.C., and gages in the upper, middle, and lower reaches of the river and backswamp within the park. Flood relations among backswamp gages exhibited different retention and recession behavior between flood plain reaches with greater hydroperiod in the lower reach than those in the upper and middle reaches of the Congaree Swamp. A flood plain inundation model was developed from gage relations to predict critical river stages and potential inundation of hiking trails on a real-time basis and to forecast the 24-hour flood In addition, tree-ring analysis was used to evaluate the effects of flood events and flooding history on forest resources at Congaree National Park. Tree cores were collected from populations of loblolly pine (Pinus taeda), baldcypress (Taxodium distichum), water tupelo (Nyssa aquatica), green ash (Fraxinus pennslyvanica), laurel oak (Quercus laurifolia), swamp chestnut oak (Quercus michauxii), and sycamore (Plantanus occidentalis) within Congaree Swamp in highand low-elevation sites characteristic of shorter and longer flood duration and related to upriver flood controls and dam operation. Ring counts and dating indicated that all loblolly pine trees and nearly all baldcypress collections in this study are postsettlement recruits and old-growth cohorts, dating from 100 to 300 years in age. Most hardwood species and trees cored for age analysis were less than 100 years old, demonstrating robust growth and high site quality. Growth chronologies of loblolly pine and baldcypress exhibited positive and negative inflections over the last century that corresponded with climate history and residual effects of Hurricane Hugo in 1989. Stemwood production on average was less for trees and species on sites with longer flood retention and hydroperiod affected more by groundwater seepage and site elevation than river floods. Water level data provided evidence that stream regulation and operations of the Saluda Dam (post-1934) have actually increased the average daily water stage in the Congaree River. There was no difference in tree growth response by species or hydrogeomorphic setting to predam and postdam flood conditions and river stage. Climate-growth analysis showed that long-term growth variation is controlled more by spring/ summer temperatures in loblolly pine and by spring/summer precipitation in baldcypress than flooding history.

South Carolina↗
USGS2016

Stochastic model for simulating Souris River Basin precipitation, evapotranspiration, and natural streamflow

The Souris River Basin is a 61,000-square-kilometer basin in the Provinces of Saskatchewan and Manitoba and the State of North Dakota. In May and June of 2011, record-setting rains were seen in the headwater areas of the basin. Emergency spillways of major reservoirs were discharging at full or nearly full capacity, and extensive flooding was seen in numerous downstream communities. To determine the probability of future extreme floods and droughts, the U.S. Geological Survey, in cooperation with the North Dakota State Water Commission, developed a stochastic model for simulating Souris River Basin precipitation, evapotranspiration, and natural (unregulated) streamflow. Simulations from the model can be used in future studies to simulate regulated streamflow, design levees, and other structures; and to complete economic cost/benefit analyses. Long-term climatic variability was analyzed using tree-ring chronologies to hindcast precipitation to the early 1700s and compare recent wet and dry conditions to earlier extreme conditions. The extended precipitation record was consistent with findings from the Devils Lake and Red River of the North Basins (southeast of the Souris River Basin), supporting the idea that regional climatic patterns for many centuries have consisted of alternating wet and dry climate states. A stochastic climate simulation model for precipitation, temperature, and potential evapotranspiration for the Souris River Basin was developed using recorded meteorological data and extended precipitation records provided through tree-ring analysis. A significant climate transition was seen around1970, with 1912–69 representing a dry climate state and 1970–2011 representing a wet climate state. Although there were some distinct subpatterns within the basin, the predominant differences between the two states were higher spring through early fall precipitation and higher spring potential evapotranspiration for the wet compared to the dry state. A water-balance model was developed for simulating monthly natural (unregulated) mean streamflow based on precipitation, temperature, and potential evapotranspiration at select streamflow-gaging stations. The model was calibrated using streamflow data from the U.S. Geological Survey and Environment Canada, along with natural (unregulated) streamflow data from the U.S. Army Corps of Engineers. Correlation coefficients between simulated and natural (unregulated) flows generally were high (greater than 0.8), and the seasonal means and standard deviations of the simulated flows closely matched the means and standard deviations of the natural (unregulated) flows. After calibrating the model for a monthly time step, monthly streamflow for each subbasin was disaggregated into three values per month, or an approximately 10-day time step, and a separate routing model was developed for simulating 10-day streamflow for downstream gages. The stochastic climate simulation model for precipitation, temperature, and potential evapotranspiration was combined with the water-balance model to simulate potential future sequences of 10-day mean streamflow for each of the streamflow-gaging station locations. Flood risk, as determined by equilibrium flow-frequency distributions for the dry (1912–69) and wet (1970–2011) climate states, was considerably higher for the wet state compared to the dry state. Future flood risk will remain high until the wet climate state ends, and for several years after that, because there may be a long lag-time between the return of drier conditions and the onset of a lower soil-moisture storage equilibrium.

Manitoba, North Dakota, Saskatchewan↗
USGS2017

Hydrogeologic and geochemical characterization and evaluation of two arroyos for managed aquifer recharge by surface infiltration in the Pojoaque River Basin, Santa Fe County, New Mexico, 2014–15

In order to provide long-term storage of diverted surface water from the Rio Grande as part of the Aamodt water rights settlement, managed aquifer recharge by surface infiltration in Pojoaque River Basin arroyos was proposed as an option. The initial hydrogeologic and geochemical characterization of two arroyos located within the Pojoaque River Basin was performed in 2014 and 2015 in cooperation with the Bureau of Reclamation to evaluate the potential suitability of these two arroyos as sites for managed aquifer recharge through surface infiltration. The selected reaches were high-gradient (average 3.0–3.5 percent) braided channels filled with unconsolidated sand and gravel-sized deposits that were generally 30–50 feet thick. Saturation was not observed in the unconsolidated channel sands in four subsurface borings but was found at 7–60 feet below the contact between the unconsolidated channel sands and the bedrock. The poorly to well-cemented alluvial deposits that make up the bedrock underlying the unconsolidated channel material is the Tesuque Formation. The individual beds of the Tesuque Formation are reported to be highly heterogeneous and anisotropic, and the bedrock at the site was observed to have variable moisture and large changes in lithology. Surface electrical-resistivity geophysical survey methods showed a sharp contrast between the electrically resistive unconsolidated channel sands and the highly conductive bedrock; however, because of the high conductivity, the resistivity methods were not able to image the water table or preferential flow paths (if they existed) in the bedrock. Infiltration rates measured by double-ring and bulk infiltration tests on a variety of channel morphologies in the study reaches were extremely large (9.7–94.5 feet per day), indicating that the channels could potentially accommodate as much as 6.6 cubic feet per second of applied water without generating surface runoff out of the reach; however, the small volume available for storage in the unconsolidated channel sands (about 410 acre-feet in the east arroyo and about 190 acre-feet in the west arroyo) and the potential for the infiltrating water to preferentially flow over the bedrock contact and out of the reach present a challenge for storing water. Although a detailed assessment of the infiltration rate of the Tesuque Formation is beyond the scope of this investigation, one double-ring infiltrometer test was conducted on an outcrop, resulting in an estimated infiltration rate of about 4 feet per day. The shallow groundwater observed in this investigation was determined to be recharged locally on the basis of groundwater elevations and geochemical and isotopic signatures. The channel sands and shallow bedrock were observed to be weathered, indicating contact with oxic groundwater following deposition. This observation was supported by whole-rock elemental analysis and mineralogy of several core samples. The downward groundwater gradient between the shallow wells and those wells screened at greater depths suggests that the shallow groundwater is recharged by local precipitation and has the potential to migrate to the deeper aquifer units. The two age-dating tracers measured in this investigation, however, demonstrate that the shallow groundwater flow paths are very slow and that the deeper flow paths are likely part of a larger regional system. The composition of the shallow, native groundwater suggests that storing water diverted from the Rio Grande is not likely to leach constituents of concern that would cause the stored water to exceed health-based U.S. Environmental Protection Agency Maximum Contaminant Levels.

New Mexico↗
USGS2024

Accounting for the fraction of carcasses outside the searched area in the estimation of bird and bat fatalities at wind energy facilities

Accurate estimation of bird and bat mortality at wind energy facilities requires accounting for carcasses that lie outside the search plots because they lie beyond the search radius or in areas within the search radius that remain unsearched due to sub-optimal search conditions such as thick vegetation, rough or dangerous ground, water, or restricted access to the land. However, carcass density is not constant around a turbine and the fraction of carcasses within the unsearched area can vary greatly depending on where the area lies relative to the turbine. The density-weighted proportion approach takes into account the changing density of carcasses around turbines to estimate the fraction of carcasses lying in unsearched areas (dwp). It involves tallying the carcasses found in concentric rings centered at the turbine, fitting a curve to the carcass densities in the rings, and dividing the integral of the curve over the area searched by the integral over the total area. Accounting for unsearched area presents special difficulties such as extrapolation beyond the search radius, spatial prediction, and model selection, which are frequently ignored or under-appreciated, potentially resulting in substantial estimation errors. A powerful new R software package (dwp) is available to perform the calculations, given the distances at which carcasses were found from turbines and a map of the searched area used to discern the fraction of the ground searched at each distance. If all ground within a given search radius has been searched, the map is simply the search radius. For more complicated search plots, other kinds of maps may be used: R polygons for plots that can be readily delineated into searched and not-searched areas (for example, searches restricted to access roads and turbine pads), GIS shape files for complicated search patterns (for example, non-uniform vegetation or ground texture resulting in spatially varying search conditions), or raster files for complicated search patterns coupled with carcass spatial distribution that depends on both distance and direction from turbines. This study discusses estimation and interpretation of dwp in the context of several realistic examples; provides guidance for use of the dwp software for doing the analyses; and addresses questions of extrapolation, spatial prediction, and model selection.

Techniques and Methods↗
USGS2004

Tree-regeneration and mortality patterns and hydrologic change in a forested karst wetland--Sinking Pond, Arnold Air Force Base, Tennessee

Multiple lines of evidence point to climate change as the driving factor suppressing tree regeneration since 1970 in Sinking Pond, a 35-hectare seasonally flooded karst depression located on Arnold Air Force Base near Manchester, Tennessee. Annual censuses of 162-193 seedling plots from 1997 through 2001 demonstrate that the critical stage for tree survival is the transition from seedling to sapling and that this transition is limited to shallow (less than 0.5 meters) ponding depths. Recruitment of saplings to the small adult class also was restricted to shallow areas. Analysis of the spatial and elevation distribution of tree-size classes in a representative 2.3-hectare area of Sinking Pond showed a general absence of overcup oak saplings and young adults in deep (ponding depth greater than 1 meter) and intermediate (ponding depth 0.5-1 meter) areas, even though overcup oak seedlings and mature trees are concentrated in these areas. Analysis of tree rings from 45 trees sampled in a 2.3-hectare spatial-analysis plot showed an even distribution of tree ages across ponding-depth classes from the 1800s through 1970, followed by complete suppression of recruitment in deep and intermediate areas after 1970. Trees younger than 30 years were spatially and vertically concentrated in a small area with shallow ponding depth, about 0.5 meter below the spillway elevation. Results of hydrologic modeling, based on rainfall and temperature records covering the period January 1854 through September 2002, show ponding durations after 1970 considerably longer than historical norms, across ponding-depth classes. This increase in ponding duration corresponds closely with similar increases documented in published analyses of streamflow and precipitation in the eastern United States and with the suppression of tree regeneration at ponding depths greater than 0.5 meter indicated by tree-ring analysis. Comparison of the simulated stage record for Sinking Pond with the ages and elevations of sampled trees shows that prolonged (200 days or more per year) inundation in more than 2 of the first 5 years after germination is inversely related to successful tree recruitment and that such inundation was rare before 1970 and common afterwards.

Water-Resources Investigations Report↗
USGS1981

Dendroclimatic estimates of a drought index for northern Virginia

A 230-year record of the Palmer drought-severity index (PDSI) was estimated for northern Virginia from variations in widths of tree rings. Increment cores were extracted from eastern hemlock, Tsuga canadensis (L.) Carr., at three locations in northern Virginia. Measurements of annual growth increments were made and converted to standardized indices of growth. A response function was derived for hemlock to determine the growth-climate relationship. Growth was positively correlated with precipitation and negatively correlated with temperature during the May-July growing season. Combined standardized indices of growth were calibrated with the July PDSI. Growth accounted for 20-30 percent of the PDSI variance. Further regressions using factor scores of combined tree growth indices resulted in a small but significant improvement. Greatest improvement was made by using factor scores of growth indices of individual trees, thereby accounting for 64 percent of the July PDSI variance in the regression. Comparison of the results with a 241-year reconstruction from New York showed good agreement between low-frequency climatic trends. Analysis of the estimated Central Mountain climatic division of Virginia PDSI record indicated that, relative to the long-term record (1746-1975), dry years have occurred in disproportionally larger numbers during the last half of the 19th century and the mid-20th century. This trend appears reversed for the last half of the 18th century and the first half of the 19th century. Although these results are considered first-generation products, they are encouraging, suggesting that once additional tree-ring chronologies are constructed and techniques are refined, it will be possible to obtain more accurate estimates of prior climatic conditions in the mid-Atlantic region.

Water Supply Paper↗
USGS2011

Growth rate and age distribution of deep-sea black corals in the Gulf of Mexico

Black corals (order Antipatharia) are important long-lived, habitat-forming, sessile, benthic suspension feeders that are found in all oceans and are usually found in water depths greater than 30 m. Deep-water black corals are some of the slowest-growing, longest-lived deep-sea corals known. Previous age dating of a limited number of black coral samples in the Gulf of Mexico focused on extrapolated ages and growth rates based on skeletal 210 Pb dating. Our results greatly expand the age and growth rate data of black corals from the Gulf of Mexico. Radiocarbon analysis of the oldest Leiopathes sp. specimen from the upper De Soto Slope at 300 m water depth indicates that these animals have been growing continuously for at least the last 2 millennia, with growth rates ranging from 8 to 22 µm yr –1 . Visual growth ring counts based on scanning electron microscopy images were in good agreement with the 14 C-derived ages, suggestive of annual ring formation. The presence of bomb-derived 14 C in the outermost samples confirms sinking particulate organic matter as the dominant carbon source and suggests a link between the deep-sea and surface ocean. There was a high degree of reproducibility found between multiple discs cut from the base of each specimen, as well as within duplicate subsamples. Robust 14 C-derived chronologies and known surface ocean 14 C reservoir age constraints in the Gulf of Mexico provided reliable calendar ages with future application to the development of proxy records.

Marine Ecology Progress Series↗
USGS2023

Fecal DNA metabarcoding shows credible short-term prey detections and explains variation in the gut microbiome of two polar bear subpopulations

This study developed and evaluated DNA metabarcoding to identify the presence of pinniped and cetacean prey DNA in fecal samples of East Greenland (EG) and Southern Beaufort Sea (SB) polar bears Ursus maritimus sampled in the spring of 2015-2019. Prey DNA was detected in half (49/92) of all samples, and when detected, ringed seal Pusa hispida was the predominant prey species, identified in 100% (22/22) of EG and 81% (22/27) of SB polar bear samples with prey DNA detected. Bearded seal Erignathus barbatus DNA was found in 19% (5/27) of SB polar bear samples for which prey DNA was detected. Prey DNA detection frequencies and relative abundances were compared to estimates from quantitative fatty acid signature analysis (QFASA) for a subset of SB polar bears. Ringed seal and bearded seal were the main prey identified by both methods, but QFASA also identified 2 cetacean prey species not found by prey DNA. Differences in DNA metabarcoding vs. QFASA results were likely related to the different dietary timescales captured by each approach, i.e. short-term vs. long-term diet, respectively. Prey DNA detection, sex/age class, and subpopulation significantly explained variation in polar bear gut bacterial composition. Polar bear samples with prey DNA detected were associated with higher abundances of the bacterial classes Clostridia and Bacilli and lower abundances of Negativicutes. Fecal DNA metabarcoding is thus useful for identifying recent prey of polar bears, complementing quantitative and likely longer-term QFASA estimates, and may help understand variation in the polar bear gut microbiome.

Marine Ecology Progress Series (MEPS)↗
USGS2018

Advancing dendrochronological studies of fire in the United States

Dendroecology is the science that dates tree rings to their exact calendar year of formation to study processes that influence forest ecology (e.g., Speer 2010 , Amoroso et al., 2017 ). Reconstruction of past fire regimes is a core application of dendroecology, linking fire history to population dynamics and climate effects on tree growth and survivorship. Since the early 20th century when dendrochronologists recognized that tree rings retained fire scars (e.g., Figure 1) , and hence a record of past fires, they have conducted studies worldwide to reconstruct the historical range and variability of fire regimes (e.g., frequency, severity, seasonality, spatial extent), the influence of fire regimes on forest structure and ecosystem dynamics, and the top-down (e.g., climate) and bottom-up (e.g., fuels, topography) drivers of fire that operate at a range of temporal and spatial scales. As in other scientific fields, continued application of dendrochronological techniques to study fires has shaped new trajectories for the science. Here we highlight some important current directions in the United States (US) and call on our international colleagues to continue the conversation with perspectives from other countries.

Fire↗
USGS2001

Recent growth of conifer species of western North America: Assessing spatial patterns of radial growth trends

We explored spatial patterns of low-frequency variability in radial tree growth among western North American conifer species and identified predictors of the variability in these patterns. Using 185 sites from the International Tree-Ring Data Bank, each of which contained 10a??60 raw ring-width series, we rebuilt two chronologies for each site, using two conservative methods designed to retain any low-frequency variability associated with recent environmental change. We used factor analysis to identify regional low-frequency patterns in site chronologies and estimated the slope of the growth trend since 1850 at each site from a combination of linear regression and time-series techniques. This slope was the response variable in a regression-tree model to predict the effects of environmental gradients and species-level differences on growth trends. Growth patterns at 27 sites from the American Southwest were consistent with quasi-periodic patterns of drought. Either 12 or 32 of the 185 sites demonstrated patterns of increasing growth between 1850 and 1980 A.D., depending on the standardization technique used. Pronounced growth increases were associated with high-elevation sites (above 3000 m) and high-latitude sites in maritime climates. Future research focused on these high-elevation and high-latitude sites should address the precise mechanisms responsible for increased 20th century growth.

Canadian Journal of Forest Research↗
USGS2008

Field Marks of a Celebration: Roger Tory Peterson's Centennial Birthday

A red letter day in my life was April 27, 1934, the day I first met Roger. A birding friend, Elisha Atkins, had invited Clinton Reynolds and me to dinner to meet a famous ornithologist. We would all be going on a field trip to Newburyport on the Massachusetts coast the next day. The dinner conversation revolved about a new field guide that Mr. Peterson had just completed and that would be available in a few days. I couldn?t wait to see it! I had been birding since 1930, keying out live birds with Chapman?s Handbook of Birds of Eastern North America (1912) and Hoffman?s Guide to the Birds of New England and Eastern New York (1904). Both books had extensive keys based on color, size, bill shape and season, and pictures of heads or feet of some species. Positive bird identification was a long and tedious process. The field trip the next day with Roger was memorable, not for finding any rare or unusual birds, but for learning how to identify birds to species at a single good glance. I recall asking Roger if he could find a ring-billed gull among a group of gulls resting on a roof beside the Merrimac River. He immediately said, ?No there aren?t any ring-bills there; they would be immediately apparent by their slimmer shape.? There was no need to check the foot color on each bird. While it is easy to say that Roger revolutionized field guides, I truly believe there are few people worldwide under the age of 90 who can really appreciate the difference between the old way of keying out birds and the instant recognition promoted by the Peterson system. Today we take for granted that amateurs can identify birds accurately. Monitoring bird populations by Breeding Bird Surveys, atlas studies, Breeding Bird Censuses, migration banding, and many other studies relies on it. None of these would be possible if we were still keying out live birds using books designed to identify dead birds in the hand.

Audubon Naturalist News↗
USGS1985

Three-dimensional P-velocity structure of he summit caldera of Newberry Volcano, Oregon

A three-dimensional high-resolution seismic study of the summit caldera of Newberry Volcano, Oregon, was conducted by the U. S. Geological Survey using an adaptation of the method applied by Nercessian et al. , (1984). Preliminary interpretation of the traveltime residuals reveals a ring of high P-velocity material coinciding with the inner ring fault system of the caldera in the upper 2 km. A zone of lower P velocities extends deeper than 2 km in the center of the caldera.

Oregon↗
USGS1997

Permo-Carboniferous sedimentary basins related to the distribution of planetary cryptoblemes

Massive/high velocity solar, galactic, and cosmic debris impacting the Earths surface may account for the enormous energy required for the formation of Permo-Carboniferous sedimentary basins and related mountain building orogenies. Analysis of satellite immagry, sea floor sonar, geophysical data, and geotectonic fabrics show a strong correlation throughout geologic time between sedimentary basin origin and planetary cryptoblemes. Cryptoblemes are subtile, multi-ringed, radial centric impact shock signatures covering the entire terrestrial surface and ocean floors, having a geometry and distribution strikingly similar to the surfaces of the lunar planetary bodies in the solar system. Investigations of Permo-Carboniferous basins show an intensely overprinted pattern of cryptoblemes coinciding with partial obliteration and elliptical compression of pre-existing basins and accompanying shock patterns. Large distorted cryptoblemes may incorporate thin skin deformation, localized sediment diagenesis, regional metamorphism, and juxtaposed exotic terrains. These data, related to basin morphogenic symmetry, suggest that large episodic impact events are the primary cause of tectonogenic features, geologic boundary formation and mass extinction episodes on the planet Earth. Plate tectonics may be only a slow moving, low energy secondary effect defined and set in motion by megacosmic accretion events. Permo-Carboniferous sediments of note are preserved or accumulated in relatively small rectangular to arcuate rift valleys and synclinal down warps, such as the Narraganset basin of Massachusetts, USA, and Paganzo basin in Argentina, S.A. These deposits and depocenters may originate from dynamic reinforcement/cancellation impact effects, as can be seen in the Basin Range of Nevada and Utah, USA. Large circular to oval sedimentary basins commonly include internal ring structures indicating post depositional subsidence and rebound adjustments with growth faulting, notable in the Illinois basin USA and Ordos basin in China. Recent impact events on the planet Jupiter, July 1994, lend increasing support towards an impact orogenic geologic paradigm on the planet Earth.

Prace - Panstwowego Instytutu Geologicznego↗
USGS2002

A preliminary evaluation of near-transducer velocities collected with low-blank acoustic Doppler current profiler

Many streams and rivers for which the US Geological Survey must provide discharge measurements are too shallow to apply existing acoustic Doppler current profiler techniques for flow measurements of satisfactory quality. Because the same transducer is used for both transmitting and receiving acoustic signals in most Doppler current profilers, some small time delay is required for acoustic "ringing" to be damped out of transducers before meaningful measurements can be made. The result of that time delay is that velocity measurements cannot be made close to the transducer thus limiting the usefulness of these instruments in shallow regions. Manufacturers and users are constantly striving for improvements to acoustic instruments which would permit useful discharge measurements in shallow rivers and streams that are still often measured with techniques and instruments more than a century old. One promising area of advance appeared to be reduction of time delay (blank) required between transmitting and receiving signals during acoustic velocity measurements. Development of a low- or zero-blank transducer by RD Instruments3 held promise that velocity measurements could be made much closer to the transducer and thus in much shallower water. Initial experience indicates that this is not the case; limitation of measurement quality appears to be related to the physical presence of the transducer itself within the flow field. The limitation may be the result of changes to water flow pattern close to the transducer rather than transducer ringing characteristics as a function of blanking distance. Results of field experiments are discussed that support this conclusion and some minimum measurement distances from transducer are suggested based on water current speed and ADCP sample modes.

Conference Paper↗
USGS2006

Carryover aquatic effects on survival of metamorphic frogs during pond emigration

In organisms with complex life cycles, physiological stressors during early life stages may have fitness-level impacts that are delayed into later stages or habitats. We tested the hypothesis that body size and date of metamorphosis, which are highly responsive to aquatic stressors, influence post-metamorphic survival and movement patterns in the terrestrial phase of an ephemeral pond-breeding frog by examining these traits in two populations of northern red-legged frogs (Rana aurora aurora). To increase variation of body size at metamorphosis, we manipulated food availability for 314 of 1045 uniquely marked tadpoles and estimated the probability that frogs survived and emigrated using concentric rings of drift fencing surrounding ponds and Bayesian capture-recapture modeling. The odds of surviving and emigrating from the ponds to the innermost drift fences, ???12 m, increased by factors of 2.20 (95% credibility intervals 1.39-4.23) and 2.54 (0.94-4.91) with each millimeter increase in snout-vent length and decreased by factors of 0.91 (0.85-0.96) and 0.89 (0.80-1.00) with each day's delay in metamorphosis for the two ponds. The odds of surviving and moving to the next ring of fencing, 12 m to ???40 m from the ponds, increased by a factor of 1.20 (0.45-4.06) with each millimeter increase in size. Our results demonstrated that body size and timing of metamorphosis relate strongly to the performance of newly metamorphosed frogs during their initial transition into terrestrial habitat. Carryover effects of aquatic stressors that reduce size and delay metamorphosis may have population-level impacts that are not expressed until terrestrial stages. Since changes in both aquatic and terrestrial systems are implicated in many amphibian declines, quantifying both immediate and delayed effects of stressors on demographic rates is critical to sound management. ?? 2006 by the Ecological Society of America.

Ecological Applications↗
USGS2009

Biodegradation of 17β-estradiol, estrone, and testosterone in stream sediments

The release of endocrine-disrupting chemicals (EDCs) in wastewater treatment plant (WWTP) effluent poses a significant threat to the ecology of surface water receptors, due to impacts on the hormonal control, sexual development, reproductive success and community structure of the indigenous aquatic organisms and associated wildlife. Among the EDCs commonly observed in WWTP effluent, the natural [e.g., 17??-estradiol (E2) and estrone (E1)] and synthetic [e.g., ethynylestradiol (EE2)] estrogens are particular concerns owing to their high endocrine reactivity in both in vitro and in vivo laboratory models. These reproductive hormones have been identified as the primary cause of estrogenic effects in wastewater effluent, with greater than 95% of the estrogen receptor agonist activity in effluent attributed to this contaminant group. The potentials for in situ biodegradation of 17??-estradiol (E2), estrone (E1), and testosterone (T) were investigated in three, hydrologically-distinct, WWTP-impacted streams in the United States. Relative differences in the mineralization of [4- 14 C] substrates were assessed in oxic microcosms containing sediment or water-only from locations upstream and downstream of the WWTP outfall in each system. Upstream samples provided insight into the biodegradative potential of sediment microbial communities that were not under the immediate impact of WWTP effluent. Upstream sediment from all three systems demonstrated significant mineralization of the "A" ring of E2, E1 and T, with the potential of T biodegradation consistently greater than of E2 and no systematic difference in the potentials of E2 and E1. Downstream samples provided insight into the impacts of effluent on reproductive hormone biodegradation. Significant "A" ring mineralization was also observed in downstream sediment, with the potentials for E1 and T mineralization being substantially depressed relative to upstream samples. In marked contrast, the potentials for E2 mineralization immediately downstream of the WWTP outfalls were more than double that of upstream samples. E2 mineralization was also observed in water, albeit at insufficient rate to prevent substantial downstream transport in the water column. The results of this study indicate that, in combination with sediment sorption processes which effectively scavenge hydrophobic contaminants from the water column and immobilize them in the vicinity of the WWTP outfall, aerobic biodegradation of reproductive hormones can be an environmentally important mechanism for nonconservative (destructive) attenuation of hormonal endocrine disruptors in effluent-impacted streams.

Conference Paper↗
USGS1979

Trees as indicators of past movements on the San Andreas Fault

Trees are sources of information about fault movements that have occurred before the earliest historical reports. This kind of evidence can be used to improve estimates of when earthquakes will recur on faults known to be seismically active and to identify active faults that have no record of movement during recent history. The approach is not new. Robert Page of the U.S Geological Survey described the effects of the 1958 earthquake on trees along the Fairweather fault in Alaska. He showed that tree rings methods could have been used to identify and to closely date this event. We undertook a similar study of the northern part of the San Andreas fault, in part because there are no historic records prior to 1906 along this segment. Earthquakes and surface rupture along faults affect trees in several different ways. Direct effects include fracturing, twisting, and tilting of trees that grown on the surface of the break. In a much wider zone along the fault, trees may be felled or topped as a result of ground motion. Among the indirect effects are tilting, felling, or burial of trees in earthquake-triggered landslides. Long-term effects may include changes in growth rate due to local hydrologic and topographic changes as well as to biological effects such as the death of neighboring trees. Under favoralbe circumstances these can be dated by tree ring methods.

California↗
USGS1989

Triumph of the Voyager mission

It had been a long, productive trip. Launched in 1977, the two Voyager spacecraft had visited three giant planets, a dozen major Moons, three ring systems with thousands of rings composed of a myriad of tiny Moonlets. The spacecraft had returned 5 trillion bits of data and over 100,000 photographs. The last encounter in our Solar System by Voyager 2 with Neptune was to be a spectacular finale to the 12-year drama.

Earthquakes & Volcanoes (USGS)↗