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At least 1,117 records · Page 62Linked to original sources
USGS2023

Assessing environmental change associated with early Eocene hyperthermals in the Atlantic Coastal Plain, USA

Eocene transient global warming events (hyperthermals) can provide insight into a future warmer world. While much research has focused on the Paleocene–Eocene Thermal Maximum (PETM), hyperthermals of a smaller magnitude can be used to characterize climatic responses over different magnitudes of forcing. This study identifies two events, namely the Eocene Thermal Maximum 2 (ETM2 and H2), in shallow marine sediments of the Eocene-aged Salisbury Embayment of Maryland, based on magnetostratigraphy, calcareous nannofossil, and dinocyst biostratigraphy, as well as the recognition of negative stable carbon isotope excursions (CIEs) in biogenic calcite. We assess local environmental change in the Salisbury Embayment, utilizing clay mineralogy, marine palynology, δ 18 O of biogenic calcite, and biomarker paleothermometry (TEX 86 ). Paleotemperature proxies show broad agreement between surface water and bottom water temperature changes. However, the timing of the warming does not correspond to the CIE of the ETM2 as expected from other records, and the highest values are observed during H2, suggesting factors in addition to p CO 2 forcing have influenced temperature changes in the region. The ETM2 interval exhibits a shift in clay mineralogy from smectite-dominated facies to illite-rich facies, suggesting hydroclimatic changes but with a rather dampened weathering response relative to that of the PETM in the same region. Organic walled dinoflagellate cyst assemblages show large fluctuations throughout the studied section, none of which seem systematically related to CIE warming. These observations are contrary to the typical tight correspondence between climate change and assemblages across the PETM, regionally and globally, and ETM2 in the Arctic Ocean. The data do indicate very warm and (seasonally) stratified conditions, likely salinity-driven, across H2. The absence of evidence for strong perturbations in local hydrology and nutrient supply during ETM2 and H2, compared to the PETM, is consistent with the less extreme forcing and the warmer pre-event baseline, as well as the non-linear response in hydroclimates to greenhouse forcing.

Atlantic Coastal Plain↗
USGS2015

Geomorphic change in the Limitrophe reach of the Colorado River in response to the 2014 delta pulse flow, United States and Mexico

A pulse of water was released from Morelos Dam into the dry streambed of the Colorado River in its former delta on March 23, 2014. Although small in relation to delta floods of a century ago, this was the first flow to reach the sea in nearly two decades. The pulse flow was significant in that it resulted from an international agreement, Minute 319, which allowed Colorado River water to be used for environmental restoration. Here we present a historical perspective of channel change and the results of geomorphic and sediment transport monitoring during the pulse flow between Yuma, Arizona and San Luis Rio Colorado, Sonora. This reach is known as the Limitrophe, because the river channel is the legal border between the United States and Mexico. Peak discharge of the pulse flow was 120 m3/s at Morelos Dam, but decreased to 71 m3/s at the southern border because of infiltration losses to the dry streambed. In contrast, flood flows in the 1980s and 1990s peaked above 600 m3/s at the southern border, and high flows above 200 m3/s were common. The sustained high flows in the 1980s caused widening and reworking of the river channel downstream through the delta. In the Limitrophe, flooding in 1993 from the Gila River basin dissected the 1980s flood surfaces, and smaller floods in the late 1990s incised the modern “active” channel within these higher surfaces. Field observations show that most geomorphic change during the pulse flow was confined to this pre-pulse, active channel. Relatively little bank erosion was evident, particularly in upstream reaches where vegetation is most dense, but new sandbars formed in areas of flow expansion. Farther downstream, localized bed scour and deposition ranged from 10s of centimeters to more than a meter, and fluvial dunes aggraded the bed in several locations. Measurable suspended-sediment transport occurred throughout the Limitrophe. Sediment concentrations peaked during the rising limb, and suspended sand concentrations suggest deposition in the lower 7 km of the Limitrophe as the channel gradient decreases by an order of magnitude. The pulse flow was small compared to historic floods, and flood magnitudes greater than the 2014 pulse flow are therefore necessary to significantly rework stable geomorphic surfaces or induce channel widening.

Arizona and California↗
USGS1983

Effects of dietary cadmium on mallard ducklings

Mallard (Anas platyrhynchos) ducklings were fed cadmium in the diet at 0, 5, 10, or 20 ppm from 1 day of age until 12 weeks of age. At 4-week intervals six males and six females from each dietary group were randomly selected, bled by jugular venipuncture, and necropsied. Significant decreases in packed cell volume (PCV) and hemoglobin (Hb) concentration and a significant increase in serum glutamic pyruvic transaminase (GPT) were found at 8 weeks of age in ducklings fed 20 ppm cadmium. Mild to severe kidney lesions were evident in ducklings fed 20 ppm cadmium for 12 weeks. No other blood chemistry measurement, hematological parameter, or tissue histopathological measurement indicated a reaction to cadmium ingestion. Body weight, liver weight, and the ratio of the femur weight to length were not affected by dietary cadmium. Femur cadmium concentration In all ducklings 12 weeks of age declined from the values detected at 4 and 8 weeks of age. Liver cadmium concentrations were significantly higher in relation to the increased dietary levels and in relation to the length of time the ducklings were fed the cadmium diets. At 12 weeks of age the cadmium concentration in liver tissue was twice that in the diet.

Environmental Research↗
USGS2007

The geology of asbestos in the United States and its practical applications

Recently, naturally occurring asbestos (NOA) has drawn the attention of numerous health and regulatory agencies and citizen groups. NOA can be released airborne by (1) the disturbance of asbestos-bearing bedrocks through human activities or natural weathering, and (2) the mining and milling of some mineral deposits in which asbestos occurs as an accessory mineral(s). Because asbestos forms in specific rock types and geologic conditions, this information can be used to focus on areas with the potential to contain asbestos, rather than devoting effort to areas with minimal NOA potential. All asbestos minerals contain magnesium, silica, and water as essential constituents, and some also contain major iron and/or calcium. Predictably, the geologic environments that host asbestos are enriched in these components. Most asbestos deposits form by metasomatic replacement of magnesium-rich rocks. Asbestos-forming environments typically display shear or evidence for a significant influx of silica-rich hydrothermal fluids. Asbestos-forming processes can be driven by regional metamorphism, contact metamorphism, or magmatic hydrothermal systems. Thus, asbestos deposits of all sizes and styles are typically hosted by magnesium-rich rocks (often also iron-rich) that were altered by a metamorphic or magmatic process. Rock types known to host asbestos include serpentinites, altered ultramafic and some mafic rocks, dolomitic marbles and metamorphosed dolostones, metamorphosed iron formations, and alkalic intrusions and carbonatites. Other rock types appear unlikely to contain asbestos. These geologic insights can be used by the mining industry, regulators, land managers, and others to focus attention on the critical locales most likely to contain asbestos.

Environmental & Engineering Geoscience↗
USGS2024

Shifting sands: The influence of coral reefs on shoreline erosion from short-term storm protection to long-term disequilibrium

Climate change is exacerbating shoreline erosion and flooding, posing significant risks to coastal communities. Although traditional coastal defenses such as seawalls, dykes, and breakwaters offer protection from these hazards, their high environmental and economic costs are driving interest in cost-competitive nature-based solutions. Coral reef restoration is a nature-based solution that may be particularly apt to mitigate tropical coastal flooding and shoreline erosion while providing benefits to local tourism, fisheries, and nature. However, the novelty of this field requires studies demonstrating the benefits of reefs for coastal protection. While the flood protection benefits of reefs have been well-documented, their effects on shoreline erosion are comparatively less understood. Here, we investigate the effects of coral reefs on shoreline erosion by comparing tropical beach responses at short and long timescales, as well as identifying important reef structural features influencing coastal erosion rates. Our analyses leveraged two key datasets created in this study: the first derived from a literature review on short-term shoreline erosion due to storm events, and another compiling >80 years of long-term erosion rates, bathymetry, habitat, and wave energy for the Hawaiian Islands of Kauaʻi, Oʻahu, and Maui. Our analyses reveal three key findings regarding the effects of reefs on shoreline erosion. Firstly, we find evidence for the role of reefs in mitigating shoreline erosion during storm events, with coral reef-protected beaches experiencing 97 % less beach volume loss than unprotected beaches. Secondly, a linear regression analysis demonstrates that coral reef structure and wave energy are important predictors of long-term shoreline erosion rates, explaining 34 % of the variation across the Hawaiian Islands. Consistent with prior research, we find beaches protected by coral reefs with shallow reef crests, wide reef flats, calmer offshore conditions, and positioned farther from the shore exhibit lower erosion rates than others. Finally, when comparing historical erosion rates of protected and unprotected beaches in Hawai'i, we find a seemingly incongruous pattern where coral reef-protected beaches eroded up to 2x faster than beaches without reefs. While the cause of the enhanced erosion is yet to be fully understood, a combination of coral reef structural degradation and sea-level rise is likely shifting the equilibrium profiles of reef-protected beaches inshore. These results emphasize the role of coral reefs in reducing coastal erosion during storm events while revealing contrasting erosion patterns over long timescales. Future studies would ideally broaden the scope to include various regions, utilize advanced sediment transport models, and undertake field experiments to deepen our understanding of coral reef-coupled shoreline dynamics.

Nature-Based Solutions↗
USGS2015

Suburbanization, estrogen contamination, and sex ratio in wild amphibian populations

Research on endocrine disruption in frog populations, such as shifts in sex ratios and feminization of males, has predominantly focused on agricultural pesticides. Recent evidence suggests that suburban landscapes harbor amphibian populations exhibiting similar levels of endocrine disruption; however the endocrine disrupting chemical (EDC) sources are unknown. Here, we show that sex ratios of metamorphosing frogs become increasingly female-dominated along a suburbanization gradient. We further show that suburban ponds are frequently contaminated by the classical estrogen estrone and a variety of EDCs produced by plants (phytoestrogens), and that the diversity of organic EDCs is correlated with the extent of developed land use and cultivated lawn and gardens around a pond. Our work also raises the possibility that trace-element contamination associated with human land use around suburban ponds may be contributing to the estrogenic load within suburban freshwaters and constitutes another source of estrogenic exposure for wildlife. These data suggest novel, unexplored pathways of EDC contamination in human-altered environments. In particular, we propose that vegetation changes associated with suburban neighborhoods (e.g., from forests to lawns and ornamental plants) increase the distribution of phytoestrogens in surface waters. The result of frog sex ratios varying as a function of human land use implicates a role for environmental modulation of sexual differentiation in amphibians, which are assumed to only have genetic sex determination. Overall, we show that endocrine disruption is widespread in suburban frog populations and that the causes are likely diverse.

Proceedings of the National Academy of Sciences of↗
USGS1983

Clutch size, reproductive success, and organochlorine contaminants in Atlantic coast black-crowned night-herons

In 1979, we gathered clutch-size and reproductive-success data on Black-crowned Night-Herons ( Nycticorax nycticorax ) nesting in three New England and two North Carolina colonies. In 1975, we gathered similar data from one of the New England and one of the North Carolina colonies. Latitudinal differences in clutch initiation were not evident. Mean clutch size was larger in the New England than in the North Carolina colonies. Mean clutch size was smaller in late nests from one New England colony studied in both years and another New England colony studied in 1979; seasonal trends in clutch size for other colonies were not found. In 1979, nest success was greater in two New England colonies than in one North Carolina colony. Within-season differences in nest success occurred but were inconsistent among colonies. In the four instances where statistical comparisons could be made, larger clutches were more successful than smaller ones in two colonies; large and small clutches had similar success in two other colonies. One egg was collected from each of several nests in each colony in 1979 for organochlorine contaminant analysis, and the fate of the remaining eggs was recorded. Concentrations of DDE and PCBs did not differ with clutch size; concentrations of PCBs were lower, however, in eggs laid late in the season. Although the data suggest an effect of DDE on hatching success in the northern more contaminated colonies, the impact of environmental contaminants on overall reproductive success appears to be minimal.

Massachusetts, North Carolina, Rhode Island↗
USGS1954

Studies on avian malaria in vectors and hosts of encephalitis in Kern County, California. I. Infections in avian hosts

An epizoological study of Plasmodium infections in wild birds of Kern County, California, in the years 1946 through 1951 greatly extended knowledge of the occurrence of these parasites and their behavior in nature. Examination of 10,459 blood smears from 8,674 birds representing 73 species resulted in the observation of Plasmodium spp. in 1,094 smears representing 888 individual birds of 27 species. Seven species of Plasmodium were found: relictum, elongatum, hexamerium, nucleophilum, polare, rouxi and vaughani. Plasmodium relictum was by far the most frequently observed species, occurring in at least 79 per cent of the infected birds. Twelve new host species are recorded for this parasite. Sufficient morphological variation was observed to indicate that two strains of this species probably exist in nature. Numerous new host records were made of plasmodia with elongate gametocytes. The finding of parasites believed to be P. rouxi in two new host species represents the first record of the occurrence of this Plasmodium outside of Algeria. Multiple smears were obtained from a number of individual birds over varying time periods. Evidence of prolonged parasitemia was unusual, but some individuals had parasitemia on consecutive months and even for three successive years. In most individuals, parasitemias were of short duration. The inoculation of blood from wild birds into canaries led to the demonstration of many infections not observed on blood smear examination of donors. Use of these two complementary techniques led to more complete host records and a truer picture of the prevalence of infection. Three age classes of birds were studied--nestling, immature (less than 1 year of age) and adult. Parasites were observed in all three groups but infections in the younger individuals were most susceptible to interpretation. As to time of onset, numerous records were obtained of infection in nestling birds. Prevalence rates in immature birds after a single season's exposure ranged from 64 to 100 per cent in the house finch and 17 to 68 per cent in the English sparrow in different areas and years. Marked differences were found in the prevalence rates in different summer months, years and areas. It is believed these differences reflect variation in a number of environmental factors. This study indicates the extensive distribution of Plasmodium infection in a wide range of wild avian hosts. The observations are of possible importance in epidemiological studies of other arthropod-borne diseases such as the viral encephalitides for which these birds serve as hosts.

California↗
USGS1983

Environmental contaminant hazards to Attwater's greater prairie-chickens

The Attwater's greater prairie-chicken ( Tympanuchus cupido attwateri ) was declared an endangered species in 1966 and exists only on the upper Gulf Coast prairie of southeast Texas. Since 1975, total numbers have declined from 2,240 to 1,456 in 1981 (Jurries 19679; W. Shifflett, Manager Attwater Prairie Chicken National Wildlife Refuge [APCNWR], personal communication). The total population of this prairie grouse is presently scattered in a norther, largely agricultural, but also urban-rangeland area of 6 counties that contained about 600 individuals in 1971, and a southern, largely rangeland, but also agricultural-urban area of 4 counties that contained about 860 individuals in 1981. During the present study, Attwater's prairie-chickens completely disappeared in Wharton and Waller counties in the northern area ( W. Shifflett, personal communication). Prairie-chickens in the northern area frequent crops of rice, soybeans, peanuts, or corn; those in the southern area frequent sorghum or cotton that are planted on or near ancestral booming grounds. The use of pesticides in the agricultural areas may have contributed to the initial decline of prairie-chicken numbers. In 1927, several hundred prairie-chickens were found dead in and near a cotton field in Wharton County shortly after it had been treated with arsenic (Lehmann and Mauermann 1963). The remains of 5 prairie-chickens were found in sorghum and soybean fields in Refugio and Colorado counties between 1975 and 1977 (R. Haeber and W. Kessler, personal communication) but were too decomposed to be analyzed for evidence of pesticide exposure. Parathion formulations had been applied to the soybeans and near the sorghum. Other pesticide use on the areas was uncertain. The objective of this study was to ascertain pesticide hazards to Attwater's greater prairie-chickens.

Texas↗
USGS2016

Influence of static habitat attributes on local and regional Rocky intertidal community structure

Rocky intertidal communities are structured by local environmental drivers, which can be dynamic, fluctuating on various temporal scales, or static and not greatly varying across years. We examined the role of six static drivers (distance to freshwater, tidewater glacial presence, wave exposure, fetch, beach slope, and substrate composition) on intertidal community structure across the northern Gulf of Alaska. We hypothesized that community structure is less similar at the local scale compared with the regional scale, coinciding with static drivers being less similar on smaller than larger scales. We also hypothesized that static attributes mainly drive local biological community structure. For this, we surveyed five to six sites in each of the six regions in the mid and low intertidal strata. Across regions, static attributes were not consistently different and only small clusters of sites had similar attributes. Additionally, intertidal communities were less similar on the site compared with the region level. These results suggest that these biological communities are not strongly influenced by the local static attributes measured in this study. An alternative explanation is that static attributes among our regions are not different enough to influence the biological communities. This lack of evidence for a strong static driver may be a result of our site selection, which targeted rocky sheltered communities. This suggests that this habitat may be ideal to examine the influence of dynamic drivers. We recommend that future analyses of dynamic attributes may best be performed after analyses have demonstrated that sites do not differ in static attributes.

Estuaries and Coasts↗
USGS2014

Body size and condition influence migration timing of juvenile Arctic grayling

Freshwater fishes utilising seasonally available habitats within annual migratory circuits time movements out of such habitats with changing hydrology, although individual attributes of fish may also mediate the behavioural response to environmental conditions. We tagged juvenile Arctic grayling in a seasonally flowing stream on the Arctic Coastal Plain in Alaska and recorded migration timing towards overwintering habitat. We examined the relationship between individual migration date, and fork length (FL) and body condition index (BCI) for fish tagged in June, July and August in three separate models. Larger fish migrated earlier; however, only the August model suggested a significant relationship with BCI. In this model, 42% of variability in migration timing was explained by FL and BCI, and fish in better condition were predicted to migrate earlier than those in poor condition. Here, the majority (33%) of variability was captured by FL with an additional 9% attributable to BCI. We also noted strong seasonal trends in BCI reflecting overwinter mass loss and subsequent growth within the study area. These results are interpreted in the context of size and energetic state-specific risks of overwinter starvation and mortality (which can be very high in the Arctic), which may influence individuals at greater risk to extend summer foraging in a risky, yet prey rich, habitat. Our research provides further evidence that heterogeneity among individuals within a population can influence migratory behaviour and identifies potential risks to late season migrants in Arctic beaded stream habitats influenced by climate change and petroleum development.

Alaska↗
USGS2023

Near-field receiving-water monitoring of trace metals and a benthic community near the Palo Alto Regional Water Quality Control Plant in south San Francisco Bay, California—2020

Trace-metal concentrations in sediment and in the clam Limecola petalum (World Register of Marine Species, 2020; formerly reported as Macoma balthica and M. petalum ), clam reproductive activity, and benthic macroinvertebrate community structure were investigated in a mudflat 1 kilometer (km) south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in south San Francisco Bay, California. This report includes the data collected by the U.S. Geological Survey (USGS) for January 2020–December 2020 (Cain and others, 2022). These data append to long-term datasets extending back to 1974. A major focus of the report is an integrated description of the 2020 data within the context of the longer, multidecadal dataset. This dataset supports the City of Palo Alto’s Near-Field Receiving- Water Monitoring Program, initiated in 1994. Silver and copper contamination substantially decreased at the site in the 1980s following the implementation by PARWQCP of advanced wastewater-treatment and source-control measures. Since the 1990s, concentrations of these elements in surface sediments have continued to decrease, although more slowly. For example, from 1994 to 2020, the minimum annual mean silver concentration—0.20 milligram per kilogram (mg/kg)—was observed in multiple years. In 2020, silver concentrations ranged from 0.18 to 0.28 mg/kg. These concentrations are 2 to 3 times higher than the regional background concentration. Presently (2020), sediment-copper concentrations appear to be near the regional background level. Over the same period (1994–2020), sedimentary iron and zinc exhibited modest decreases. Sedimentary aluminum, chromium, mercury, nickel, and selenium have not exhibited any trend. Since 1994, silver and copper concentrations in L. petalum have varied seasonally, apparently in response to a combination of site-specific metal exposures and cyclic growth and reproduction, as reported previously. Seasonal patterns for other elements, including chromium, mercury, nickel, selenium, and zinc, generally were similar in timing and magnitude as those for silver and copper. Downward trends in the silver and zinc concentrations in L. petalum during 1994–2020 were evident and appeared to be related to the general physiological condition of the clam, indicated by a condition index. Biological effects of elevated silver and copper contamination at the Palo Alto site have been interpreted from data collected during and after the recession of these contaminants. Concentrations of both elements in the soft tissues of L. petalum decreased with sedimentary copper and silver. This pattern was associated with changes in the reproductive activity of L. petalum , as well as the structure of the benthic invertebrate community. Reproductive activity of L. petalum increased as metal concentrations in L. petalum decreased (Hornberger and others, 2000), and presently is stable with almost all animals initiating reproduction in the fall and spawning the following spring. Analyses of the benthic community structure indicate that the infaunal invertebrate community has shifted from one dominated by several opportunistic species when silver and copper exposures were highest to one in which the species abundance is more evenly distributed, a pattern that indicates a more stable community that is subjected to fewer stressors. Importantly, this long-term change is unrelated to other metals and other measured environmental factors, including salinity and sediment composition. In addition, two of the opportunistic species ( Ampelisca abdita and Streblospio benedicti ) that brood their young and live on the surface of the sediment in tubes have shown a continual decrease in dominance coincident with the decrease in metals. Both species had short-lived rebounds in abundance in 2008, 2009, and 2010 and showed signs of increasing abundance in 2020. Heteromastus filiformis (a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying its eggs on or in the sediment) showed a concurrent increase in dominance and, in the last several years before 2008, showed a stable population. H. filiformis abundance increased slightly from 2011 to 2012 and returned to pre-2011 numbers in 2020. The reproductive mode of most species that were present in 2020 was indicative of species that were capable of movement either as pelagic larvae or as mobile adults. Although oviparous species were lower in number in this group, the authors hypothesize that these species will return slowly as more species move back into the area. The use of functional ecology was highlighted in the 2020 benthic community data, which showed that the animals that have now returned to the mudflat are those that can respond successfully to a physical, nontoxic disturbance. Today, community data show a mix of species that consume the sediment, or filter feed, those that have pelagic larvae that must survive landing on the sediment, and those that brood their young. The long-term recovery observed after the 1970s can be ascribed to the decrease in sediment pollutants.

California↗
USGS1999

Protocol and practice in the adaptive management of waterfowl harvests

Waterfowl harvest management in North America, for all its success, historically has had several shortcomings, including a lack of well-defined objectives, a failure to account for uncertain management outcomes, and inefficient use of harvest regulations to understand the effects of management. To address these and other concerns, the U.S. Fish and Wildlife Service began implementation of adaptive harvest management in 1995. Harvest policies are now developed using a Markov decision process in which there is an explicit accounting for uncontrolled environmental variation, partial controllability of harvest, and structural uncertainty in waterfowl population dynamics. Current policies are passively adaptive, in the sense that any reduction in structural uncertainty is an unplanned by-product of the regulatory process. A generalization of the Markov decision process permits the calculation of optimal actively adaptive policies, but it is not yet clear how state-specific harvest actions differ between passive and active approaches. The Markov decision process also provides managers the ability to explore optimal levels of aggregation or "management scale" for regulating harvests in a system that exhibits high temporal, spatial, and organizational variability. Progress in institutionalizing adaptive harvest management has been remarkable, but some managers still perceive the process as a panacea, while failing to appreciate the challenges presented by this more explicit and methodical approach to harvest regulation. Technical hurdles include the need to develop better linkages between population processes and the dynamics of landscapes, and to model the dynamics of structural uncertainty in a more comprehensive fashion. From an institutional perspective, agreement on how to value and allocate harvests continues to be elusive, and there is some evidence that waterfowl managers have overestimated the importance of achievement-oriented factors in setting hunting regulations. Indeed, it is these unresolved value judgements, and the lack of an effective structure for organizing debate, that present the greatest threat to adaptive harvest management as a viable means for coping with management uncertainty. Copyright ?? 1999 by The Resilience Alliance.

Conservation Ecology↗
USGS2004

Distribution and relative abundance of fishes in littoral areas of Chief Joseph Reservoir, Columbia River

We surveyed fish assemblages in littoral areas of Chief Joseph Reservoir of the upper Columbia River to aid in understanding this ecosystem. Fish distributions and abundances were examined during April-July 1999 in relation to environmental conditions in the reservoir. We also compared the fish assemblages in Chief Joseph reservoir in 1999 to a past study conducted during 1974-1975, and to assemblages in other areas of the Columbia River. During 67 hr of electrofishing and 78 beach seine hauls in Chief Joseph Reservoir, 7460 fishes representing 8 families were collected. The majority of the catch was native – northern pikeminnow; redside shiners; longnose, bridgelip, and largescale suckers; and sculpins. The most abundant introduced species was walleye, and one species, rainbow trout, was mostly of net-pen origin. Larger sizes of suckers and northern pikeminnow were most abundant in the upper reservoir, likely due to upstream spawning migrations. The lower reservoir contained greater abundances of smaller fishes, and this area had lower flows, smaller substrates, and more complex shorelines that offered these fishes refugia. Only adult suckers displayed significant differences in abundances related to substrate. The relative abundances of species appeared to have changed since the 1970s, when the dominant fishes were northern pikeminnow, peamouth, largescale suckers, and walleye. Fish assemblage differences between Chief Joseph Reservoir and lower Columbia River reservoirs were also evident due to the morphology of the reservoir, its more northerly location, and the lack of fish passage facilities at Chief Joseph Dam. Our study is one of the few descriptions of fishes in the upper Columbia Rivers.

Washington↗
USGS2024

Predator disturbance contributed to Common Murre Uria aalge breeding failures in Cook Inlet, Alaska following the 2014–2016 Pacific marine heatwave

The 2014-2016 Pacific marine heatwave caused unprecedented die-offs and multi-year reproductive failures for Common Murres Uria aalge along the west coast of North America. Lingering impacts, such as declines in colony attendance and productivity, have persisted at some colonies following the heatwave and are attributed largely to changes in prey availability and quality. Here, we present evidence of an additional, top-down mechanism contributing to Common Murre breeding failures on Gull Island (Alaska): disturbance of nesting birds by aerial predators and associated egg depredation. We collected time-lapse images over five murre breeding seasons (2016-2020) on Gull Island to document the frequency, duration, and intensity of disturbances caused by aerial predators, as well as to quantify disturbance-associated egg depredation. To identify seasonal and inter-annual variability of disturbances, we calculated a daily disturbance index and compared years using generalized additive models. In all years, Bald Eagles Haliaeetus leucocephalus were the primary cause of disturbance, which led to periods of prolonged colony abandonment by murres and facilitated high levels of murre egg depredation by Glaucous-winged Gulls Larus glaucescens and Herring Gulls L. argentatus . We found that the seasonality of disturbance was an important factor in determining egg depredation rates. In years when disturbance levels were high and persisted later in the season, the colony experienced complete breeding failures due to disturbance-associated egg depredation. Our study revealed that the response of nesting murres to a strong environmental perturbation, such as the Pacific marine heatwave, can be complex and involve multiple stressors from both bottom-up and top-down factors.

Alaska↗
USGS2011

Evidence for foraging -site fidelity and individual foraging behavior of pelagic cormorants rearing chicks in the Gulf of Alaska

The Pelagic Cormorant ( Phalacrocorax pelagicus ) is the most widespread cormorant in the North Pacific, but little is known about its foraging and diving behavior. However, knowledge of seabirds' foraging behavior is important to understanding their function in the marine environment. In 2006, using GPS dataloggers, we studied the foraging behavior of 14 male Pelagic Cormorants rearing chicks on Middleton Island, Alaska. For foraging, the birds had high fidelity to a small area 8 km north of the colony. Within that area, the cormorants' diving activity was of two distinct kinds—near-surface dives (1–6 m) and benthic dives (28–33 m). Individuals were consistent in the depths of their dives, either mostly shallow or mostly deep. Few showed no depth preference. Dive duration, time at maximum depth, and pauses at the water surface between consecutive dives were shorter for shallow dives than for deep dives. The cormorants made dives of both types throughout the day, but the frequency of deep dives increased toward evening. Maximum foraging range was 9 km; maximum total distance traveled per trip was 43.4 km. Trip durations ranged from 0.3 to 7.7 hr. Maximum depth of a dive was 42.2 m, and duration of dives ranged from 4 to 120 sec. We found that Pelagic Cormorants at Middleton Island were faithful to one particular foraging area and individuals dived in distinct patterns. Distinct, specialized foraging behavior may be advantageous in reducing intra- and interspecific competition but may also render the species vulnerable to changing environmental conditions.

Alaska↗
USGS2008

Cyanide speciation at four gold leach operations undergoing remediation

Analyses have been made of 81 effluents from four gold leach operations in various stages of remediation to identify the most-persistent cyanide species. Total cyanide and weak acid-dissociable (WAD) cyanide were measured using improved methods, and metals known to form stable cyanocomplexes were also measured. Typically, total cyanide greatly exceeded WAD indicating that cyanide was predominantly in strong cyanometallic complexes. Iron was generally too low to accommodate the strongly complexed cyanide as Fe(CN) 6 3- or Fe(CN) 6 4- , but cobalt was abundant enough to implicate Co(CN) 6 3- or its dissociation products (Co(CN) 6-x (H 2 O) x (3-x)- ). Supporting evidence for cobalt-cyanide complexation was found in tight correlations between cobalt and cyanide in some sample suites. Also, abundant free cyanide was produced upon UV illumination. Iron and cobalt cyanocomplexes both photodissociate; however, the iron concentration was insufficient to have carried the liberated cyanide, while the cobalt concentration was sufficient. Cobalt cyanocomplexes have not previously been recognized in cyanidation wastes. Their identification at four separate operations, which had treated ores that were not especially rich in cobalt, suggests that cobalt complexation may be a common source of cyanide persistence. There is a need for more information on the importance and behavior of cobalt cyanocomplexes in ore-processing wastes at gold mines.

California;Nevada;New Mexico↗
USGS2018

Before-after, control-impact analysis of evidence for the impacts of water level on Walleye, Northern Pike and Yellow Perch in lakes of the Rainy-Namakan complex (MN, USA and ON, CA)

Water level (WL) fluctuations in lakes influence many aspects of ecosystem processes. Concern about the potential impact of WL fluctuations on fisheries was one of the factors that motivated the decision in 2000 to alter the management of WL in the Rainy-Namakan reservoir complex (on the border between the U.S. state of Minnesota and the Canadian province of Ontario). We used a Before-After, Control-Impact (BACI) framework to identify potential impacts of the change in WL management to Walleye, Northern Pike and Yellow Perch catch per unit effort (CPUE). The CPUE of these species from 1990±1999 and from 2005±2014 were compared in four impact lakes (Lake Kabetogama, Namakan Lake, Rainy Lake and Sand Point Lake) and two control lakes (Lake of the Woods and Lake Vermilion) using a simple Bayesian model. Changes in fish CPUE in the impact lakes were often similar to changes that occurred in at least one control lake. The only change that was not similar to changes in control lakes was an increase of Yellow Perch in Lake Kabetogama. The two control lakes often differed substantially from each other, such that if only one had been available our conclusions about the role of WL management on fisheries would be very different. In general, identifying cause-and-effect relationships in observational field data is very difficult, and the BACI analysis used here does not specify a causative mechanism, so co-occurring environmental and management changes may obscure the effect of WL management.

Minnesota, Ontario↗