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At least 901 records · Page 50Linked to original sources
USGS2022

Virtual special issue of recent advances on gas hydrates scientific drilling in Alaska

Gas hydrate refers to a non-stoichiometric clathrate that forms spontaneously in the natural environment whenever sufficient quantities of gases of appropriate size (most commonly methane) interact with abundant water under specific conditions of temperature and pressure. (1,2) Such conditions occur wherever the shallow geothermal gradient has been suppressed by either deepwater or thick permafrost, allowing for relatively low temperatures to coexist with elevated pressures. The volume of gas hydrate on Earth is difficult to constrain, (3) but it is sufficient that gas hydrate is a meaningful potential component of (1) the long-term natural cycling of carbon, (2) the nearer term environmental changes in response to warming climates, (4) and (3) future energy supply systems. Since the initial recognition of gas hydrate as an abundant component in nature in the late 1960s, a series of scientific drilling expeditions conducted by both the Integrated Ocean Discovery Program (and successors) and national research and development programs in Canada, Japan, China, the United States, South Korea, and others (5) have explored the occurrence and nature of gas hydrates. In particular, the desire for expanded energy supply options to support the economic development and energy security for nations around the globe is currently motivating a broad range of laboratory and numerical simulation studies in support of an ongoing series of field-based scientific tests of the potential commercial viability of gas extraction from natural gas hydrate deposits. (6)

Journal of Energy & Fuels↗
USGS1955

Engineering geology as applied to highway construction

A geologic study of the site for a relocated segment of State Highway 93 northwest of Denver Colo., was made by by the Engineering Geology Branch of the U.S. Geological Survey as a demonstration of the applicability of geologic mapping to problems of highway construction. The relocated segment provides access to the Rocky Flats plant of the Atomic Energy Commission. The geologic conditions along five miles of the relocation route were examined. In most places apparently well-indurated sandstones of the Upper Cretaceous Fox Hills sandstone and Laramie formation can be excavated without using explosives. The intersection of a six foot thick coal seam in the roadbed in one proposed cut was predicted and removal and replacement with more suitable subgrade material was recommended. Near Marshall the alignment crosses three northeast-trending normal faults which do not adversely affect the highway. Clay minerals with expanding properties are present in some of the claystones of the Laramie, and special measures must be taken to ensure that ground water will not seep into them and cause swelling beneath the roadbed. Late Tertiary or Early Quaternary gravel cap pediments along the mountain front. Ground water issuing from seeps and springs found at the contact between these gravels and the underlying bedrock should be intercepted and removed from beneath the roadbed.

Colorado↗
USGS2014

Physiological condition of juvenile wading birds in relation to multiple landscape stressors in the Florida Everglades: effects of hydrology, prey availability, and mercury bioaccumulation

The physiological condition of juvenile birds can be influenced by multiple ecological stressors, and few studies have concurrently considered the effects of environmental contaminants in combination with ecological attributes that can influence foraging conditions and prey availability. Using three temporally distinct indices of physiological condition, we compared the physiological response of nestling great egrets ( Ardea alba ) and white ibises ( Eudocimus albus ) to changing prey availability, hydrology (water depth, recession rate), and mercury exposure in the Florida Everglades. We found that the physiological response of chicks varied between species and among environmental variables. Chick body condition (short-term index) and fecal corticosterone levels (medium-term) were influenced by wetland water depth, prey availability, region, and age, but not by mercury contamination. However, mercury exposure did influence heat shock protein 70 (HSP70) in egret chicks, indicating a longer-term physiological response to contamination. Our results indicate that the physiological condition of egret and ibis chicks were influenced by several environmental stressors, and the time frame of the effect may depend on the specialized foraging behavior of the adults provisioning the chicks.

Florida↗
USGS1968

Late Eocene nonmarine diatoms from the Beaver Divide area, Fremont County, Wyoming

The Beaver Divide is a high escarpment of Tertiary nonmarine strata in central Wyoming separating the Sweetwater Plateau from the relatively low-lying Wind River Basin. The Wagon Bed Formation of middle and late Eocene age and the Beaver Divide Conglomerate Member of the White River Formation-this member being of early Oligocene (Chadronian) age--are exposed near the top of the Beaver Divide in Fremont County, Wyo., about 23 miles southeast of Riverton. The upper part of the Wagon Bed Formation, dated as late Eocene (Uintan) age by Van Houten on the basis of vertebrate fossils, contains a highly silicified fresh-water limestone stratigraphically high in the section with a poorly preserved diatom assemblage. The Beaver Divide Conglomerate Member contains large blocks of similar white limestone, some of which have an assemblage of diatoms the same as that of the Wagon Bed Formation but showing excellent preservation. Both the Wagon Bed limestone and the limestone blocks from the Beaver Divide Conglomerate Member have virtually the same assemblages of nonmarine gastropods. A study of the local geology indicates that a marked erosional topography formed on the Wagon Bed strata before deposition of the Beaver Divide sediments. The Beaver Divide limestone blocks were derived from nearby exposures of the Wagon Bed Formation. The diatom assemblage under consideration was originally deposited in the Wagon Bed limestone and is, therefore, late Eocene rather than early Oligocene in age. This represents the earliest known assemblage of nonmarine diatoms from North America. The diatom assemblage of the Wagon Bed Formation consists of 27 new species, two species known previously from the upper Miocene of France, and five species still found in living assemblages. One new genus containing two species also occurs in the deposit. The Wagon Bed diatom assemblage is strikingly distinct from later Tertiary fresh-water assemblages in that many diatom genera common to the younger deposits are totally lacking in this Eocene formation. These genera may be absent because of a highly specialized paleoecology during deposition of the Wagon Bed limestone, but the meager evidence provided by the few still-living species suggests nothing more specific than deposition in a temperate circumneutral lake.

Wyoming↗
USGS2019

Comparison of continuous and interrupted lampricide block toxicity to sea lamprey and lake sturgeon

Lake Sturgeon ( Acipenser fulvescens , LST) is a state, provincial, and tribal species of special concern that is sensitive to lampricides used in sea lamprey control. As such, there is significant interest in the Great Lakes fisheries community to develop alternative sea lamprey ( Petromyzon marinus , SL) control approaches to minimize impacts on LST for applicable LST producing streams. Currently, lampricides are applied continuously to streams for 10 to 14 hours to achieve at least a 9-hour lampricide block at or above the SL minimum lethal concentration (MLC). Once the application of lampricides are initiated it usually takes 1-4 hours for the lampricide concentration to build to the target concentration during treatments depending on the flow dynamics of the stream. An interrupted lampricide block, wherein the treatment consists of two lampricide blocks (cumulative MLC of at least 9 hours) with a break in the middle, has been shown to decrease burrowing mayfly ( Hexagenia limbata ) mortality and resulted in no change to MLC when interruptions were up to 12 hours in duration. This study compared mortality of LST and SL during continuous and interrupted lampricide blocks with the goal of establishing whether an interrupted lampricide block treatment could be used to protect LST while maintaining treatment efficacy. Results show that there was no difference in toxicity to larval SL or LST between the interrupted block and continuous exposures. No differences were detected among calculated LC25s andLC50s for LST in the interrupted block tests compared to the continuous block tests during laboratory and streamside bioassays. An interrupted block field trial on Eliza Creek resulted in high mortality among caged larval SL (99.5%); however, posttreatment surveys estimated the treatment kill at 83.5% compared to >99% from the two previous continuous block treatments (2007, 2001). This suggests a substantial decrease in treatment effectiveness when using the interrupted block strategy. The lack of separation in toxicity between LST and SL under continuous interrupted block treatment and the reduced efficacy of the interrupted treatment block combine to make this treatment method a less desirable option.

Report↗
USGS2015

Documenting 35 years of land cover change: Lago Cachet Dos drainage, Chile

The U.S. Geological Survey (USGS) Special Applications Science Center is monitoring temporal changes at the Colonia Glacier and Lago Cachet Dos, Northern Patagonia Icefield of southern Chile. This location is one of the newest international sites in the USGS Global Fiducial Program (GFP)—a program which provides systematic monitoring of dynamic and environmentally critical areas with high-resolution imagery (http://gfp.usgs.gov/). In 2008, Lago Cachet Dos began experiencing glacial lake outburst floods (GLOFs) during which the entire pool of water (about 200 million cubic meters) rapidly drains from the lake and flows south-southeast through the Colonia Glacier. These catastrophic events cause massive erosion of valley-fill deposits and consequent upstream expansion of Lago Cachet Dos towards Lago Cachet Uno. Panchromatic and multispectral images for 1979, 2007, and 2014 highlight the dramatic changes that have occurred at this site over a 35-year period. The lake was smallest in 1979, when the Colonia Glacier was at its maximum extent during the study period. Between 1979 and 2007, the glacier shrank causing an increase in the surface area of the lake. The size of the lake increased substantially, from 2.98 square kilometers (km 2 ) in 1979 to 4.41 km 2 in 2014, primarily due to erosion of valley-fill deposits upstream of its northern edge by the 15 GLOFs that occurred between April 2008 and February 2014. Ongoing studies of the Colonia Glacier and Lago Cachet Dos are focused on providing real-time monitoring of Lago Cachet Dos lake levels, understanding the history of advances and retreats of the Colonia Glacier, and determining the physical mechanisms and hazards associated with the GLOFs that come from Lago Cachet Dos.

Lago Cachet Dos↗
USGS2023

Introduction to the special section on seismoacoustics and seismoacoustic data fusion

A variety of geophysical hazards (e.g., volcanic activity, earthquakes, mass movements, marine storms, bolides) and anthropogenic sources (e.g., chemical and nuclear explosions, mining blasts, rocket launches) can release energy as mechanical waves in the ground, ocean, and atmosphere (Arrowsmith et al., 2010; Campus and Christie, 2009). Due to the mechanical coupling between a planetary body, its ocean, and its atmosphere, waves can propagate across these interfaces (Ben-Menahem and Singh, 1981) and carry information about the source and the media they propagated through. The field of seismoacoustics, driven by geophysical observations of both seismic and low-frequency acoustic (infrasound) waves, has several interdisciplinary applications. Observations of both seismic and infrasonic waves can be used to discriminate between atmospheric and subsurface events, such as sonic booms and earthquakes. Moreover, seismoacoustic analyses can provide useful information for the source characterization of shallow anthropogenic events, such as underground or surface explosions, volcanic, and tectonic events (e.g., Arrowsmith et al., 2020; Assink et al., 2016; de Groot-Hedlin and Hedlin, 2019; Matoza et al., 2009). Similarly, remote observations (e.g., on regional seismic and infrasonic arrays) can help monitor natural events such as volcanic eruptions and provide additional details about eruption dynamics. Recent works additionally suggest that infrasound can be used to discriminate between different volcanic processes (Watson et al., 2022). Finally, looking outwards, the study of seismo-acoustics has been a particularly valuable tool for planetary science (e.g., Krishnamoorthy et al., 2018; Martire et al., 2018; Krishnamoorthy et al., 2019; Martire et al., 2020; Garcia et al., 2020; Brissaud et al., 2021).

Bulletin of the Seismological Society of America↗
USGS1902

The Geology and Petrography of Crater Lake National Park

Twenty years ago Crater Lake was unknown to the general public, but since then a knowledge of its remarkable features has been spread abroad through the press, and Congress recognized its worth as an educational feature and made it a national park by the act approved May 22, 1902. As defined in the bill, the park is 'bounded north by the parallel forty-three degrees four minutes north latitude, south by forty-two degrees forty-eight minutes north latitude, east by the meridian one hundred and twenty-two degrees west longitude, and west by the meridian one hundred and twenty-two degrees sixteen minutes west longitude, having an area of two hundred and forty-nine square miles'. The Ashland sheet of United States Geological Survey, on the scale of 4 miles to 1 inch, includes the area lying between meridians 122 deg and 123 deg and parallels 42 deg and 43 deg. This map includes the region between Ashland and Crater Lake. On account of the great scientific interest of Crater Lake a special map, known as the Crater Lake special sheet, was prepared on the scale of 1 mile to an inch, including the country immediately adjacent to Crater Lake, between meridians 122 deg and 122 deg 15' and parallels 42 deg 50' and 43 deg 4'. From these two maps the accompanying map of the Crater Lake National Park (Pl. 1) has been prepared. The two papers published here refer practically to the whole region included in the National Park. The one, Part I, treats primarily of the geology, the development of the great volcano, Mount Mazama, and its collapse, which gave birth to Crater Lake; the other, Part II, deals with the petrography, and gives a special description of the various rocks occurring in the park. Origin of the name Mount Mazama - A great impetus to the spread of information concerning Crater Lake was given by the Mazamas of Portland, Oreg., who held a meeting at the lake in August, 1896, which attracted many visitors. The principal features in the history of the lake had previously been made out, and the Mazamas, recognizing the fact that the great peak which was nearly destroyed in preparing the pit for the lake had no name, gave it the name of their own society. Upon the rim of the lake are a number of small peaks, each having its own designation. The term Mount Mazama refers to the whole rim encircling the lake. It is but a mere remnant of the once lofty peak, the real Mount Mazama, which rose far into the region of eternal snow. To get a basis for reconstructing the original Mount Mazama it is necessary to study in detail the structure and composition of its foundation, now so attractively displayed in the encircling cliffs of Crater Lake.

Oregon↗
USGS2002

Long-term dynamics of winter and summer annual communities in the Chihuahuan Desert

Winter and summer annuals in the Chihuahuan Desert have been intensively studied in recent years but little is known about the similarities and differences in the dynamics between these two communities. Using 15 yr of census data from permanent quadrats, this paper compared the characteristics and temporal dynamics of these two distinct, spatially co-existent but temporally segregated communities. Although the total number of summer annual species recorded during our 15 yr of observation was higher than winter annuals, the mean number of species observed each year was higher in the winter community. The winter community exhibited lower temporal variation in total plant abundance and populations of individual species, lower species turnover rate and higher evenness than the summer community. The rank abundances of species in winter were significantly positively correlated for a period of up to 7 yr while in summer significant positive correlations in rank abundance disappeared after 2 to 3 yr. The higher seasonal species diversity (i.e. number of species observed in each season) in winter rather than the overall special pool (over 15 yr) may be responsible for the greater community stability of winter annuals. The difference in long-term community dynamics between the two communities of annual plants are likely due to the differences in total species pool, life history traits (e.g. seed size), and seasonal climatic regimes.

Portal↗
USGS2020

Occurrence of a suite of stream-obligate amphibians in timberlands of Mendocino County, California, examined using environmental DNA

Stream-obligate amphibians are important indicators of ecosystem health in the Pacific Northwest, but distributional information to improve forest management is lacking in many regions. We analyzed archived DNA extracted from water samples in 60 pools in streams on private timberlands in Mendocino County, California, for 3 California Species of Special Concern—Coastal Tailed Frogs ( Ascaphus truei ), Foothill Yellow-legged Frogs ( Rana boylii ), and Southern Torrent Salamanders ( Rhyacotriton variegatus )—to better understand their distributions in the region. Detection probabilities for eDNA of Foothill Yellow-legged Frogs and Coastal Tailed Frogs were positively influenced by water temperature. eDNA occurrence for both frogs was affected by whether silt or organic matter was a dominant substrate in the sampled pool, and Foothill Yellow-legged Frog eDNA occurrence was also affected by water temperature. Foothill Yellow-legged Frog eDNA occurrence had a strong, positive association with water temperature, with occurrence unlikely below 14°C and very likely above 16°C, and a positive association with silt or organic substrates in pools, which was likely an indicator of higher-order stream reaches. In contrast, Coastal Tailed Frogs had a negative association with silt or organic substrates. Historical visual detections were generally congruent with findings using eDNA, but differences highlight important areas for further study. We did not detect Southern Torrent Salamanders using eDNA at any sites. Our study reinforces that ecological relationships of these species are varied, and shows the importance of maintaining the integrity of streams with diverse characteristics for conserving stream amphibians.

California↗
USGS1986

The Breeding Bird Survey: Its first fifteen years, 1965-1979

The Breeding Bird Survey (BBS) is an ongoing cooperative program sponsored jointly by the U.S. Fish and Wildife Service and the Canadian Wildlife Service. Its main purpose is to estimate population trends of the many species of birds that nest in North America north of Mexico and that migrate across international boundaries. This survey provides information, both locally by ecological or political regions and on a continental scale, on (1) short-term population changes that can be correlated with specific weather incidents, (2) recovery periods following catastrophic declines, (3) normal year-to-year variations, (4) long-term population trends, and (5) invasions of exotics. The BBS also permits detailed computer mapping of relative abundance of each species, either year by year to show changes in distribution and relative abundance, or the average over a period of years. It provides base-line data with which more intensive local studies can be compared. For biogeographic studies it provides uniform sampling of bird populations by major physiographic regions across the continent. In conjunction with the Audubon Christmas Bird Count, it permits comparison of summer and winter distribution of species that winter in the United States. Most species of North American birds migrate across international boundaries, especially those shared with Canada, Mexico, and the Soviet Union. As part of our responsibility under treaties with these nations, the U.S. Fish and Wildlife Service has developed the BBS to monitor avian population changes so that any adverse trends can be detected early. This provides the opportunity to determine the reasons for any increase or decrease, to define geographic areas in which changes are greatest, to study correlations between avian population changes and land-use changes, and to make recommendations for controlling undesirable bird population trends. For example, the BBS can be used to detect and estimate the extent of losses resulting from widespread use of pesticides, and to reveal whether major population changes of a given species (e.g., Dickcissel) in certain States are related to a continental decline or are merely a result of population shifts within the breeding range. Effects of urban and suburban expansion are often reflected in the loss of forest interior birds. Population trends for 230 species as well as several avian genera and families are discussed and graphed in this report. For most of these species, regional and well as continental trends are shown. The three major regions discussed are the Eastern, Central, and Western, bounded by the Mississippi River and the eastern base of the Rocky Mountains. Additional graphs for certain States or physiographic regions are included for selected species of special interest. The following paragraphs summarize general trends in the major bird families. The native herons in general are maintaining their populations, whereas the exotic Cattle Egret continues its geographic spread and its steady increase. Waterfowl as a group are stable or increasing. Although most widespread species of hawks are on the increase, the rarer species show evidence of decline. Among the gallinaceous birds, the greatest change was a sharp drop in Northern Bobwhite as a result of the exceptionally cold winters of 1976-77 and 1977-78 in the Ohio Valley and the Middle Atlantic States. Killdeer populations, except for a minor decline during these two winters, showed strong increases except in the West. American Woodcock were poorly sampled by the BBS because they were relatively inactive during daylight. Common Snipe and the other common shorebirds that nest in the United States and southern Canada exhibited stable or increasing populations, especially in the Eastern and Central regions. Herring Gull counts varied dramatically and irregularly from year to year. Laughing Gulls increased along the Atlantic coast and Franklin's Gulls declined in the interior of the continen

Resource Publication↗
USGS1989

Slope movements triggered by heavy rainfall, November 3–5, 1985, in Virginia and West Virginia, U.S.A.

Study of slope movements triggered by the storm of November 3–5, 1985, in the central Appalachian Mountains, U.S.A., has helped to define the meteorologic conditions leading to slope movements and the relative importance of land cover, bedrock, surficial geology, and geomorphology in slope movement location. This long-duration rainfall at moderate intensities triggered more than 1,000 slope movements in a 1,040-km 2 study area. Most were shallow slips and slip-flows in thin colluvium and residuum on shale slopes. Locations of these failures were sensitive to land cover and slope aspect but were relatively insensitive to topographic setting. A few shallow slope movements were triggered by the same rainfall on interbedded limestone, shale, and sandstone. Several large debris slide-avalanches were triggered in sandstone regolith high on ridges in areas of the highest measured rainfall. Most of these sites were on slopes that dip 30 to 35° and lie parallel to bedding planes, presumably the sites of least stability.

Virginia, West Virginia↗
USGS2016

Logging impacts on avian species richness and composition differ across latitudes relative to foraging and breeding habitat preferences

Understanding the causes underlying changes in species diversity is a fundamental pursuit of ecology. Animal species richness and composition often change with decreased forest structural complexity associated with logging. Yet differences in latitude and forest type may strongly influence how species diversity responds to logging. We performed a meta-analysis of logging effects on local species richness and composition of birds across the world and assessed responses by different guilds (nesting strata, foraging strata, diet, and body size). This approach allowed identification of species attributes that might underlie responses to this anthropogenic disturbance. We only examined studies that allowed forests to regrow naturally following logging, and accounted for logging intensity, spatial extent, successional regrowth after logging, and the change in species composition expected due to random assembly from regional species pools. Selective logging in the tropics and clearcut logging in temperate latitudes caused loss of species from nearly all forest strata (ground to canopy), leading to substantial declines in species richness (up to 27% of species). Few species were lost or gained following any intensity of logging in lower-latitude temperate forests, but the relative abundances of these species changed substantially. Selective logging at higher-temperate latitudes generally replaced late-successional specialists with early-successional specialists, leading to no net changes in species richness but large changes in species composition. Removing less basal area during logging mitigated the loss of avian species from all forests and, in some cases, increased diversity in temperate forests. This meta-analysis provides insights into the important role of habitat specialization in determining differential responses of animal communities to logging across tropical and temperate latitudes.

Biological Reviews↗
USGS2006

An integrated chronostratigraphic data system for the twenty-first century

Research in stratigraphy is increasingly multidisciplinary and conducted by diverse research teams whose members can be widely separated. This developing distributed-research process, facilitated by the availability of the Internet, promises tremendous future benefits to researchers. However, its full potential is hindered by the absence of a development strategy for the necessary infrastructure. At a National Science Foundation workshop convened in November 2001, thirty quantitative stratigraphers and database specialists from both academia and industry met to discuss how best to integrate their respective chronostratigraphic databases. The main goal was to develop a strategy that would allow efficient distribution and integration of existing data relevant to the study of geologic time. Discussions concentrated on three major themes: database standards and compatibility, strategies and tools for information retrieval and analysis of all types of global and regional stratigraphic data, and future directions for database integration and centralization of currently distributed depositories. The result was a recommendation to establish an integrated chronostratigraphic database, to be called Chronos, which would facilitate greater efficiency in stratigraphic studies (http://www.chronos.org/) . The Chronos system will both provide greater ease of data gathering and allow for multidisciplinary synergies, functions of fundamental importance in a variety of research, including time scale construction, paleoenvironmental analysis, paleoclimatology and paleoceanography. Beyond scientific research, Chronos will also provide educational and societal benefits by providing an accessible source of information of general interest (e.g., mass extinctions) and concern (e.g., climatic change). The National Science Foundation has currently funded a three-year program for implementing Chronos.. ?? 2006 Geological Society of America. All rights reserved.

Special Paper of the Geological Society of America↗
USGS2017

Manatee grazing impacts on a mixed species seagrass bed

The endangered manatee Trichechus manatus is one of few large grazers in seagrass systems. To assess the long-term impacts of repeated grazing on seagrasses, we selected a study site within Kennedy Space Center in the northern Banana River, Brevard County, Florida, that was typically grazed by large numbers of manatees in spring. Two 13x13 m manatee exclosures and 2 paired open plots of equal size were established at the study site in October 1990. Shoot counts, biomass, and species composition of the co-dominant seagrass species, Syringodium filiforme and Halodule wrightii , were sampled 3 times per year in all 4 plots between October 1990 and October 1994. We used a Bayesian modelling approach, accounting for the influence of depth, to detect treatment (exclosed vs. open) effects. S. filiforme shoot counts, total biomass, and frequency of occurrence significantly increased in the exclosures. By July 1993, mean biomass values in the exclosures (167 g dry wt m -2 ) greatly exceeded those in the open plots (28 g dry wt m -2 ). H. wrightii decreased in the exclosures by 1994. Initially, both S. filiforme and H. wrightii responded positively to release from manatee grazing pressure. As S. filiforme continued to become denser in the exclosures, it gradually replaced H. wrightii . Our findings may be helpful to biologists and managers interested in predicting seagrass recovery and manatee carrying capacity of repeatedly grazed seagrass beds in areas of special significance to manatees and seagrass conservation.

Marine Ecology Progress Series↗
USGS2003

Sea otter studies in Glacier Bay National Park and Preserve: annual report 2002

Since 1995, the number of sea otters in Glacier Bay proper has increased from around 5 to more than 1200. Sea otter distribution is mostly limited to the Lower Bay, south of Sandy Cove, and is not continuous within that area. Concentrations occur in the vicinity of Sita Reef and Boulder Island and between Pt. Carolus and Rush Pt. on the west side of the Bay, although there have been occasional sightings north of Sandy Cove (Figure 1). Large portions of the Bay remain unoccupied by sea otters, but recolonization is occurring rapidly. Most prey recovered by sea otters in Glacier Bay are ecologically, commercially, or socially important species. In 2002 sea otter diet consisted of 35% clam, 26% mussel, 3% crab, 3.0% snail, 2% starfish, 11% urchins, 2% other, and 20% unidentified. Dominant clam species include the butter clam, Saxidomus gigantea , the Greenland cockle, Serripes groenlandicus , and the littleneck clam, Protothaca staminea . Urchins are primarily green urchins, Strongylocentrotus droebachiensis , and the mussel is Modiolus modiolus . Crabs observed in 2002 include the Dungeness, Cancer magister , the kelp crab Pugettia gracilis , and the helmet crab, Telmessus cherigonus . Although we characterize diet at broad geographic scales, we have previously found diet to vary between sites separated by as little as several hundred meters. Dietary variation among and within sites can reflect differences in prey availability as well as individual specialization. We estimated species composition, density, biomass, and sizes of subtidal clams, urchins, and mussels at 13 sites in Glacier Bay and 5 sites in nearby Port Althorp, where sea otters have been present for at least 20 years. All sites were selected based on the presence of abundant clam siphons and the absence of sea otters (Glacier Bay) or abundant shell litter and the presence of sea otters (Port Althorp). Glacier Bay sites were selected to achieve a broad geographic sample of dense subtidal clam beds within Glacier Bay prior to occupation and foraging by sea otters. Port Althorp sites were chosen to achieve a representative sample of subtidal clam beds already under prolonged foraging pressure by sea otters. There was no direct evidence of otter foraging at any of our Glacier Bay sampling sites. In Glacier Bay, we sampled 15,338 bivalves (average of 1,180/site) representing 14 species of clam, 2 species of mussel, and a single scallop and we sampled 6,917 urchins (average of 513/site). In Port Althorp, we sampled 1,034 bivalves (average of 207/site) representing 14 species of clam. We found only 5 urchins, all S. droebachiensis . Mean densities and biomass of all subtidal clams were significantly greater in Glacier Bay (59.2 and 99/0.25m 2 compared to Port Althorp (10.3 and 5.8/0.25m 2 (p<0.002 for both). Our contrasts of subtidal clam populations between Glacier Bay and Port Althorp suggest that clam densities will likely decline by about a factor of six and that clam biomass estimates will decline by more than a factor of ten. Numerically dominant species of clams, P. staminea , S. gigantea , Macoma sp. and Mya sp. were all significantly greater in density and biomass in Glacier Bay, while C. nutalli density was low but significantly higher in Port Althorp. Subtidal clam species diversity was significantly greater in Port Althorp compared to Glacier Bay, although this may simply reflect habitat differences. Sea urchin densities were high in Glacier Bay, while in Port Althorp urchins were virtually absent. Sea otters are now well established in limited areas of the lower portions of Glacier Bay. It is likely that distribution and numbers of sea otters will continue to increase in Glacier Bay in the near future. Glacier Bay supports large and diverse populations of clams that are largely unexploited by sea otters at present. It is predictable that the density and sizes of clam populations will decline in response to otter predation. This will result in fewer opportunities for human harvest, but will also trigger ecosystem level changes, as prey for other predators, such as octopus, sea stars, fishes, birds and mammals are modified. Sea otters will also modify benthic habitats through excavation of sediments required to extract burrowing infauna such as clams. Effects of sediment disturbance by foraging sea otters are not understood. Glacier Bay also supports large populations of other preferred sea otter prey, such as king ( Paralithodes sp. ), tanner ( Chionoecetes sp. ) and dungeness ( Cancer magister ) crabs and green sea urchins ( S. droebachiensis ). As the colonization of Park waters by sea otters continues, it is also likely that dramatic changes will occur in the species composition, abundance, and size class distribution of many components of the nearshore marine ecosystem. Many of the changes will occur as a direct result of predation by sea otters. Others will result from indirect or cascading effects of sea otter foraging, such as increased kelp production and modified prey availability for other nearshore predators. Without recognizing and quantifying the extent of change initiated by the colonization of Glacier Bay by sea otters, management of nearshore resources will be severely constrained for many decades.

Alaska↗
USGS2015

Applied Geochemistry Special Issue on Environmental geochemistry of modern mining

Environmental geochemistry is an integral part of the mine-life cycle, particularly for modern mining. The critical importance of environmental geochemistry begins with pre-mining baseline characterization and the assessment of environmental risks related to mining, continues through active mining especially in water and waste management practices, and culminates in mine closure. The enhanced significance of environmental geochemistry to modern mining has arisen from an increased knowledge of the impacts that historical and active mining can have on the environment, and from new regulations meant to guard against these impacts. New regulations are commonly motivated by advances in the scientific understanding of the environmental impacts of past mining. The impacts can be physical, chemical, and biological in nature. The physical challenges typically fall within the purview of engineers, whereas the chemical and biological challenges typically require a multidisciplinary array of expertise including geologists, geochemists, hydrologists, microbiologists, and biologists. The modern mine-permitting process throughout most of the world now requires that potential risks be assessed prior to the start of mining. The strategies for this risk assessment include a thorough characterization of pre-mining baseline conditions and the identification of risks specifically related to the manner in which the ore will be mined and processed, how water and waste products will be managed, and what the final configuration of the post-mining landscape will be. In the Fall 2010, the Society of Economic Geologists held a short course in conjunction with the annual meeting of the Geological Society of America in Denver, Colorado (USA) to examine the environmental geochemistry of modern mining. The intent was to focus on issues that are pertinent to current and future mines, as opposed to abandoned mines, which have been the focus of numerous previous short courses. The geochemical challenges of current and future mines share similarities with abandoned mines, but differences also exist. Mining and ore processing techniques have changed; the environmental footprint of waste materials has changed; environmental protection has become a more integral part of the mine planning process; and most historical mining was done with limited regard for the environment. The 17 papers in this special issue evolved from the Society of Economic Geologists’ short course. The relevant geochemical processes encompass the source, transport, and fate of contaminants related to the life cycle of a mine. Contaminants include metals and other inorganic species derived from geologic sources such as ore and solid mine waste, and substances brought to the site for ore processing, such as cyanide to leach gold. Factors, such as mine-waste mineralogy, hydrologic setting, mine-drainage chemistry, and microbial activity, that affect the hydrochemical risks from mining are reviewed by Nordstrom et al. In another paper, Nordstrom discusses baseline characterization at mine sites in a regulatory framework, and emphasizes the influence of mineral deposits in producing naturally elevated concentrations of many trace elements in surface water and groundwater. Surface water quality in mineralized watersheds is influenced by a number of processes that act on daily (diel) cycles and can produce dramatic variations in trace element concentrations as described by Gammons et al. Pre-mining baseline characterization studies should strive to capture the magnitude of these diel variations. Desbarats et al., using a case study of mine drainage from a gold mine, illustrate how elements that commonly occur as negatively charged species (anions) in solution, such as arsenic as arsenate, behave in an opposite fashion than most metals, which occur as positively charged species (cations). Significant improvement in the understanding of factors that influence the toxicity of metals to aquatic organisms in surface water has highlighted the importance of aqueous chemistry, particularly dissolved organic carbon, as described by Smith et al. Stream sediment contamination is another important pathway for affecting aquatic organisms, as reviewed by Besser et al. Understanding and predicting environmental consequences from mining begins with knowing the mineralogy and mineral reactivity of the ore, the wastes, and of secondary minerals formed later. Jamieson et al. review the importance of mineralogical studies in mine planning and remediation. A number of types of site-specific studies are needed to identify environmental risks related to individual mines. Lapakko reviews the general framework of mine waste characterization studies that are integral to the mine planning process. Hageman et al. present a comparative study of several static tests commonly used to characterize mine waste. The mining and ore processing practices employed at a specific mine site will vary on the basis of the commodities being targeted, the geology of the deposit, the geometry of the deposit, and the mining and ore processing methods used. Thus, these factors, in addition to the waste management practices used, can result in a variety of end-member mine waste features, each of which has its own set of challenges. Open pit mines and underground mines require waste rock to be removed to access ore. Waste rock presents unique problems because the rock is commonly mineralized at sub-economic grades and has not been processed to remove potentially problematic minerals, such as pyrite. Amos et al. examine the salient aspects of the geochemistry of waste rock. Mill tailings – the waste material after ore minerals have been removed – are a volumetrically important solid waste at many mine sites. Their fine grain size and the options for their management make their behavior in the environment distinct from that of waste rock. Lindsay et al. describe some of these differences through three case-study examples. Subaqueous disposal of tailings is another option described by Moncur et al. Cyanide leaching for gold extraction is a common method throughout the world. Johnson describes environmental aspects of cyanidation. Uranium mining presents unique environmental challenges, particularly since in-situ recovery has seen widespread use. Campbell et al. review the environmental geochemistry of uranium mining and current research on bioremediation. Ore concentrates from many types of metal mining undergo a pyrometallurgical technique known as smelting to extract the metal. Slag is the result of smelting, and it may be an environmental liability or a valuable byproduct, as described by Piatak et al. Finally, the open pits that result from surface mining commonly reach below the water table. At the end of mining, these pits may fill to form lakes that become part of the legacy of the mine. Castendyk et al., in two papers, review theoretical aspects of the environmental limnology of pit lakes. They also describe approaches that have been used to model pit lake water balance, wall-rock contributions to pit lake chemistry, pit lake water quality, and limnological processes, such as vertical mixing, through the use of three case studies.

Applied Geochemistry↗
USGS2020

Ecological interfaces between land and flowing water: Themes and trends in riparian research and management

This paper provides an overview of past, present and future themes for research and management of riparian zones, often relating to papers within this Wetlands Special Feature. Riparian research expanded in the United States around 1980 with themes that recognized (1) damage from excessive livestock, or (2) damage from river damming and diversion, and (3) the beneficial capacity of riparian buffers to intercept and assimilate nutrients and other water contaminants. Research expanded globally in the 1990s, with themes including (4) plant life history requirements and (5) reliance on fluvial geomorphic dynamics that enable riparian rejuvenation. Resource managers recognized that riparian areas provide (6) rich wildlife habitats (7) along with valued ecosystem services, (8) which encouraged conservation and restoration initiatives, (9) including environmental flow regimes. Floodplains are (10) vulnerable to invasive plants and management has included biocontrol such as for Tamarix in the American Southwest. Into the twenty-first century, (11) climate change is advancing, and riparian ecosystems may be especially impacted due to the compound challenges from increasing water demand and declining summer flows. As an emerging opportunity, (12) while reservoirs submerge floodplain vegetation, reservoir deltas may support compensatory riparian wetlands. (13) Studies increasingly utilize remote sensing tools including satellite imagery, LiDAR and unmanned aircraft systems, and (14) the coordination of large data sets invites digital ecology, including artificial intelligence and machine learning. Since riparian zones are centres for human activities, (15) there are opportunities for citizen science, social media and internet applications, which will increasingly democratize riparian research and management.

Wetlands↗