Biological impacts on wolves of exploitation and control: a response
Explore the source record for details and available documents.
Wildlife Society Annual Conference↗
SEARCH · Search USGS
Results for “Biological Control”
Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Seasonal periphyton response to low-level nutrient exposure in a least disturbed mountain stream, the Buffalo River, Arkansas
Like most streams located in the Ozark Plateaus, the Buffalo River in Arkansas generally has excellent water quality. Water-quality conditions in Big Creek, however, a major tributary of the middle Buffalo River, have been less favorable than that of other Buffalo River tributaries. Concerns regarding the influence of water quality in Big Creek on the Buffalo River magnified in 2013 when a large confined animal feeding operation (CAFO) began operating in the watershed. In response to these concerns, the U.S. Geological Survey compared monthly nutrient concentrations and seasonal periphyton assemblage metrics of a site on Big Creek downstream of the CAFO, two Buffalo River control sites upstream of the confluence with Big Creek, and three Buffalo River test sites downstream of the confluence with Big Creek. In addition to identifying potential nutrient patterns and periphyton responses along a low-level nutrient exposure gradient, the study determined how nutrient contributions from Big Creek (and the CAFO) are affecting ecological conditions and consequent ecosystem services in the Buffalo River. Nutrient and periphyton data exhibited more temporal than spatial variability. Nutrient concentrations were generally highest of all sites at the Big Creek site. Concentrations at the five sites on the Buffalo River were typically low (near laboratory reporting limits), and concentrations at the three test sites rarely exceeded those of the two control sites. An index developed with three ecologically relevant periphyton metrics (oligotrophic taxa and Homoeothrix percent relative abundance and mesotrophic diatoms percent taxa richness) suggested that nutrient uptake at sites downstream of the Big Creek-Buffalo River confluence resulted in subtle shifts in downstream periphyton assemblages. The periphyton index of biological integrity at control sites was slightly and generally more favorable compared to test sites. Even so, when periphyton data were considered in conjunction with both hydrology and water-quality data, the negative consequences of antecedent high flows and associated scouring exceeded the potential positive effects that low-level nutrients had on algal productivity. These findings emphasize the importance of comparing biological and chemical data across extended temporal scales, particularly when working with low-level nutrient gradients.
Arkansas↗
Global patterns of tree stem growth and stand aboveground wood production in mangrove forests
Mangrove forests provide important ecological and economic services including carbon sequestration and storage. The conservation and restoration of mangroves are expected to play an important role in mitigating climate change, and understanding the factors influencing mangrove stem growth and wood production are important in predicting and improving mangrove carbon sequestration and responses to environmental change. In this study, we collected data of individual diameter at breast height (DBH) growth rate and stand level aboveground wood production in both non-plantation (commonly termed as natural) mangroves and mangrove plantations across the world. Climatic factors, proxies of edaphic factors, as well as biological factors (e.g. mangrove species) were included as explanatory variables in the analyses to determine factors influencing the global patterns of tree growth rate and stand wood production of mangroves. Using hierarchical Classification and Regression Tree (CART) analysis we found interactions among environmental and biological factors in controlling mangrove tree growth rate and stand wood production. We also found different global patterns of tree growth rate and stand wood production between non-plantation mangroves and plantations. Climatic conditions (precipitation of driest season, precipitation seasonality) were the most important factors influencing the global pattern of tree DBH growth rate in non-plantation mangroves, with edaphic and biological characteristics also playing a role under specific climatic conditions. The global pattern of stand wood production in non-plantation mangroves was primarily determined by stand mean DBH growth rate of individual trees. However, in mangrove plantations management measures, specifically species selection and planting density, were the most important factors influencing the global patterns of tree growth rate and stand wood production. Our study provides parameters for a global estimation of long-term carbon sequestration in both non-plantation mangroves and mangrove plantations. In addition, our results help us better predict the dynamics of tree growth and carbon sequestration of non-plantation mangroves under changing climate.
Forest Ecology and Management↗
Dreissenid mussel research priorities workshop
Currently, dreissenid mussels have yet to be detected in the northwestern part of the United States and western Canada. Infestation of one of the jurisdictions within the mussel-free Pacific Northwest would likely have significant economic, societal and environmental implications for the entire region. Understanding the biology and environmental tolerances of dreissenid mussels, and effectiveness of various management strategies, is key to prevention. On November 4-5, 2015, the Aquatic Bioinvasion Research and Policy Institute and the Center for Lakes and Reservoirs at Portland State University, the US Geological Survey, and the Pacific States Marine Fisheries Commission, convened a Dreissenid Mussel Research Priorities Workshop funded by the Great Northern Landscape Conservation Cooperative. The purpose of the workshop was to review dreissenid research priorities in the 2010 Quagga-Zebra Mussel Action Plan for Western U.S. Waters, reassess those priorities, incorporate new information and emerging trends, and develop priorities to strategically focus research efforts on zebra and quagga mussels in the Pacific Northwest and ensure that future research is focused on the highest priorities. It is important to note that there is some repetition among dreissenid research priority categories (e.g., prevention, detection, control, monitoring, and biology). Workshop participants with research experience in dreissenid mussel biology and management were identified by a literature review. State and federal agency managers were also invited to the workshop to ensure relevancy and practicality of the workshop outcomes. A total of 28 experts (see sidebar) in mussel biology, ecology, and management attended the workshop.
Conference Paper↗
Biological low pH Mn(II) oxidation in a manganese deposit influenced by metal-rich groundwater
The mechanisms, key organisms, and geochemical significance of biological low-pH Mn(II) oxidation are largely unexplored. Here, we investigated the structure of indigenous Mn(II)-oxidizing microbial communities in a secondary subsurface Mn oxide deposit influenced by acidic (pH 4.8) metal-rich groundwater in a former uranium mining area. Microbial diversity was highest in the Mn deposit compared to the adjacent soil layers and included the majority of known Mn(II)-oxidizing bacteria (MOB) and two genera of known Mn(II)-oxidizing fungi (MOF). Electron X-ray microanalysis showed that romanechite [(Ba,H 2 O) 2 (Mn 4+ ,Mn 3+ ) 5 O 10 ] was conspicuously enriched in the deposit. Canonical correspondence analysis revealed that certain fungal, bacterial, and archaeal groups were firmly associated with the autochthonous Mn oxides. Eight MOB within the Proteobacteria , Actinobacteria , and Bacteroidetes and one MOF strain belonging to Ascomycota were isolated at pH 5.5 or 7.2 from the acidic Mn deposit. Soil-groundwater microcosms demonstrated 2.5-fold-faster Mn(II) depletion in the Mn deposit than adjacent soil layers. No depletion was observed in the abiotic controls, suggesting that biological contribution is the main driver for Mn(II) oxidation at low pH. The composition and species specificity of the native low-pH Mn(II) oxidizers were highly adapted to in situ conditions, and these organisms may play a central role in the fundamental biogeochemical processes (e.g., metal natural attenuation) occurring in the acidic, oligotrophic, and metalliferous subsoil ecosystems.
Applied and Environmental Microbiology↗
A river-scale Lagrangian experiment examining controls on phytoplankton dynamics in the presence and absence of treated wastewater effluent high in ammonium
Phytoplankton are critical component of the food web in most large rivers and estuaries, and thus identifying dominant controls on phytoplankton abundance and species composition is important to scientists, managers, and policymakers. Recent studies from a variety of systems indicate that ammonium ( NH + 4 ) in treated wastewater effluent decreases primary production and alters phytoplankton species composition. However, these findings are based mainly on laboratory and enclosure studies, which may not adequately represent natural systems. To test effects of effluent high in ammonium on phytoplankton at the ecosystem scale, we conducted whole-river–scale experiments by halting discharges to the Sacramento River from the regional wastewater treatment plant (WWTP), and used a Lagrangian approach to compare changes in phytoplankton abundance and species composition in the presence (+EFF) and absence (−EFF) of effluent. Over 5 d of downstream travel from 20 km above to 50 km below the WWTP, chlorophyll concentrations declined from 15–25 to ∼2.5 μg L −1 , irrespective of effluent addition. Benthic diatoms were dominant in most samples. We found no significant difference in phytoplankton abundance or species composition between +EFF and −EFF conditions. Moreover, greatest declines in chlorophyll occurred upstream of the WWTP where NH + 4 concentrations were low. Grazing by clams and zooplankton could not account for observed losses, suggesting other factors such as hydrodynamics and light limitation were responsible for phytoplankton declines. These results highlight the advantages of conducting ecosystem-scale, Lagrangian-based experiments to understand the dynamic and complex interplay between physical, chemical, and biological factors that control phytoplankton populations.
California↗
Seasonal patterns in nutrients, carbon, and algal responses in wadeable streams within three geographically distinct areas of the United States, 2007-08
The U.S. Geological Survey determined seasonal variability in nutrients, carbon, and algal biomass in 22 wadeable streams over a 1-year period during 2007 or 2008 within three geographically distinct areas in the United States. The three areas are the Upper Mississippi River Basin (UMIS) in Minnesota, the Ozark Plateaus (ORZK) in southern Missouri and northern Arkansas, and the Upper Snake River Basin (USNK) in southern Idaho. Seasonal patterns in some constituent concentrations and algal responses were distinct. Nitrate concentrations were greatest during the winter in all study areas potentially because of a reduction in denitrification rates and algal uptake during the winter, along with reduced surface runoff. Decreases in nitrate concentrations during the spring and summer at most stream sites coincided with increased streamflow during the snowmelt runoff or spring storms indicating dilution. The continued decrease in nitrate concentrations during summer potentially is because of a reduction in nitrate inputs (from decreased surface runoff) or increases in biological uptake. In contrast to nitrate concentrations, ammonia concentrations varied among study areas. Ammonia concentration trends were similar at UMIS and USNK sampling sites with winter peak concentrations and rapid decreases in ammonia concentrations by spring or early summer. In contrast, ammonia concentrations at OZRK sampling sites were more variable with peak concentrations later in the year. Ammonia may accumulate in stream water in the winter under ice and snow cover at the UMIS and USNK sites because of limited algal metabolism and increased mineralization of decaying organic matter under reducing conditions within stream bottom sediments. Phosphorus concentration patterns and the type of phosphorus present changes with changing hydrologic conditions and seasons and varied among study areas. Orthophosphate concentrations tended to be greater in the summer at UMIS sites, whereas total phosphorus concentrations at most UMIS and USNK sites peaked in the spring during runoff and then decreased through the remainder of the sampling period. Total phosphorus and orthophosphate concentrations in OZRK streams peaked during summer indicating a runoff-based source of both nutrients. Orthophosphate concentrations may increase in streams in the late summer when surface runoff composes less of total streamflow, and when groundwater containing orthophosphate becomes a more dominant source in streams during lower flows. Seston chlorophyll a concentrations were greatest early in the growing season (spring), whereas the spring runoff events coincided with reductions in benthic algal chlorophyll a biomass likely because of scour of benthic algae from the channel bottom that are entrained in the water column during that period. Nitrate, ammonia, and orthophosphate concentrations also decreased during that same period, indicating dilution in the spring during runoff events. The data from this study indicate that the source of water (surface runoff or groundwater) to a stream and the intensity of major runoff events are important factors controlling instream concentrations. Biological processes appear to affect nutrient concentrations during more stable lower flow periods in later summer, fall, and winter when residence time of water in a channel is longer, which allows more time for biological uptake and transformations. Management of nutrient conditions in streams is challenging and requires an understanding of multiple factors that affect in-stream nutrient concentrations and biological uptake and growth.
Scientific Investigations Report↗
Trace elements in Corbicula fluminea from the San Joaquin River, California
(i) Trace element concentrations in soft tissue of the benthic bivalve, Corbicula fluminea, from the San Joaquin River and its major tributaries were examined during the primary irrigation season in relation to the spatial variation in concentrations of major, minor and trace constituents in riverwater and sediments. (ii) Selenium concentrations in Corbicula from perennial flow reaches of the San Joaquin River and its major tributaries varied directly with the solute (??? 0.45 ??m) Se concentrations of riverwater. Elevated concentrations occurred in clams from sites with substantial discharge originating as subsurface drainage and irrigation return flows. Both tissue and solute Se concentrations declined from June through the end of the primary irrigation season. (iii) Arsenic concentrations in Corbicula from perennial flow reaches of the San Joaquin River varied directly with the HNO3-extractable (pH 2) As:Fe ratio of suspended matter, providing evidence that sorption to oxyhydroxide surfaces is an important control on the biological availability of As. However, Corbicula from several tributaries draining alluvium derived from the Sierra Nevada had lower As concentrations than would be predicted by the relation developed for perennial flow sites of the San Joaquin River. Arsenic concentrations in Corbicula from the Tuolumne and Merced Rivers and upstream reaches of the San Joaquin River were higher than in clams from the downstream perennial flow reaches of the San Joaquin River. Concentrations of As in clams from downstream perennial flow reaches of the San Joaquin River increased from June through the end of the primary irrigation season. (iv) Mercury concentrations in Corbicula were elevated in upstream reaches of the San Joaquin River, in the Merced and Tuolumne Rivers, and in tributaries draining the Coast Ranges. Mean Cd and Cu concentrations in Corbicula were elevated in the Merced and Tuolumne Rivers, Orestimba Creek and a perennial flow reach of the San Joaquin River which receives water directly from the Delta Mendota Canal. Concentrations of Ni in clams from the San Joaquin River decreased downstream of the Delta Mendota Pool. (v) Boron and Mo were not accumulated by Corbicula despite high solute concentrations (means as high as 2960 ??g B l-1 and 9 ??g Mo l-1) in riverwater during the primary irrigation season. This bivalve may not be an appropriate bioindicator of B and Mo enrichment. Concentrations of Cr, Pb, Ag, V and Zn in Corbicula exhibited little geographic variability in the drainage. (vi) Regression analysis revealed no clear evidence of synergistic or antagonistic interactions among As, Cd, Cu, Hg, Ni and Se in their uptake by Corbicula.
Conference Paper↗
Overview of SAX99: Environmental considerations
A 1-km2 area located 2 km off the Florida Pan-handle (30??22.6???N; 86??38.7???W) was selected as the site to conduct high-frequency acoustic seafloor penetration, sediment propagation, and bottom scattering experiments [1]. Side scan, multibeam, and normal incidence chirp acoustic surveys as well as subsequent video surveys, diver observations, and vibra coring, indicate a uniform distribution of surficial and subbottom seafloor characteristics within the area. The site, in 18-19 m of water, is characterized by 1-2-m thick fine-to-medium clean sand and meets the logistic and scientific requirements specified for the acoustic experiments. This paper provides a preliminary summary of the meteorological, oceanographic, and seafloor conditions found during the experiments and describes the important physical and biological process that control the spatial distribution and temporal changes in these characteristics.
IEEE Journal of Oceanic Engineering↗
Approaches to modeling weathered regolith
Sustainable soils are a requirement for maintaining human civilizations ( Carter and Dale 1974 ; Lal 1989 ). However, as the “most complicated biomaterial on the planet” ( Young and Crawford 2004 ), soils represent one of the most difficult systems to understand and model with respect to chemical, physical, and biological coupling over time (Fig. 1 ). Despite the complexity of these interactions, certain patterns in soil properties and development are universally observed and have been used in soil science as a means for classification. Elemental, mineralogical, or isotopic concentrations in soils plotted versus depth beneath the land surface comprise such patterns. Soil depth profiles are often reported for solid soil materials, and, less frequently, for solutes in soil pore waters. These profiles cross a large range in spatial scales that traditionally have been studied by different disciplines. For example, shallow, biologically active horizons are commonly defined as the soil zone in agronomic studies whereas the mobile layer of the regolith is referred to as soil in geomorphological studies. In contrast, many geochemical studies target chemical weathering to tens or even hundreds of meters in depth, sometimes extending the definition of “soils” to include the entire regolith down to parent bedrock or alluvium. Soil profiles also exhibit a large range in temporal scales ( Amundson 2004 ; Brantley 2008b ). Solid-state profiles document chemical and mineralogical changes integrated over the time scales of evolution of regolith from protolith. This “geologic time” can vary from tens to hundreds of years for weathered material developed on moraines deposited by active glaciers ( Anderson et al. 1997 ), to millions or possibly hundreds of millions of years of regolith evolution as documented in laterites and bauxites on stable cratons ( Nahon 1986 ). In contrast, solute profiles reflect much shorter time scales corresponding to the residence time of the soil water which commonly ranges from days to decades ( Stonestrom et al. 1998 ). Factors impacting soil minerals can therefore be related to geologically old processes while those impacting pore waters are related to contemporary processes. We first discuss a geochemical frame work for modeling soil profiles, including a simple scheme that depends on the extent of enrichment or depletion. Such profiles are comprised of reaction fronts affected by chemical, hydrologic, geologic and biologic processes that control soil evolution. We then present a hierarchy of models that have been used to interpret both solid state and solute compositions in regolith. The more simple approaches to model depletion in soils, using analytical models, are first described. The most elementary of these is a linear model that calculates rate constants from the slopes of either solid or solute weathering gradients: these rate constants represent lumped parameters that describe weathering in terms of an integrated reaction rate. Two other analytical models are then presented that have been used to fit solid state elemental profiles with exponential and sigmoidal functions. All of these analytical approaches are derived for models of soils as containing a limited number of components, phases, and species. At a more complex level, numerical models are then presented to elucidate how kinetic and transport parameters as well as chemical, hydrologic, and physical soil data can be incorporated. We consider two forms of these models, first relatively simple spreadsheet calculators and then more sophisticated multi-component, multi-phase reactive-transport numerical codes. Our treatment of reactive transport modeling is relatively cursory, in recognition of the treatment in the chapter by Steefel and Maher (2009 , this volume). Because these models incorporate more phases, components, and species than the other approaches and explicitly model the more fundamental reaction mechanisms involved, they generally have a greater need for parameterization. In our conclusion section, we discuss how this hierarchy of approaches can yield generalizations about soils that are often complementary.
Reviews in Mineralogy and Geochemistry↗
The Sea-Floor Mapping Facility at the U.S. Geological Survey Woods Hole Field Center, Woods Hole, Massachusetts
Researchers of the sea-floor mapping facility at the U.S. Geological Survey (USGS) Woods Hole Field Center in Woods Hole, Mass., use state-of-the-art technology to produce accurate geologic maps of the sea floor. In addition to basic bathymetry and morphology, sea-floor maps may contain information about the distribution of sand resources, patterns of coastal erosion, pathways of pollutant transport, and geologic controls on marine biological habitats. The maps may also show areas of human impacts, such as disturbance by bottom fishing and pollution caused by offshore waste disposal. The maps provide a framework for scientific research and provide critical information to decisionmakers who oversee resources in the coastal ocean.
Fact Sheet↗
Unearthing Secrets of the Forest
Forests are a defining feature for large areas of the Pacific northwestern United States from northern California to Alaska. Coniferous temperate rainforests in the western Cascade and coastal mountain ranges are appreciated for their aesthetic value and abundant natural resources. Few people recognize the riches beneath the forest floor; yet, soil is a key ecosystem component that makes each type of forest unique. Soils harbor immense biological diversity and control the release of water and nutrients that support life above ground. Understanding how carbon and nutrients cycle in forests, known as forest biogeochemistry, is crucial for evaluating forest productivity, composition, diversity, and change. At the U.S. Geological Survey (USGS) Forest and Rangeland Ecosystem Science Center, research in the Terrestrial Ecosystems Laboratory focuses on nutrient cycling in five themes: climate change, nutrition and sustainability, fire effects, restoration, and forest-stream linkages. This research is essential to understand the entire forest ecosystem and to use the best science available to make informed policy and management decisions.
Fact Sheet↗
Daily and seasonal variability of pH, dissolved oxygen, temperature, and specific conductance in the Colorado River between the forebay of Glen Canyon Dam and Lees Ferry, northeastern Arizona, 1998-99
The productivity of the trout fishery in the tailwater reach of the Colorado River downstream from Glen Canyon Dam depends on the productivity of lower trophic levels. Photosynthesis and respiration are basic biological processes that control productivity and alter pH and oxygen concentration. During 1998?99, data were collected to aid in the documentation of short- and long-term trends in these basic ecosystem processes in the Glen Canyon reach. Dissolved-oxygen, temperature, and specific-conductance profile data were collected monthly in the forebay of Glen Canyon Dam to document the status of water chemistry in the reservoir. In addition, pH, dissolved-oxygen, temperature, and specific-conductance data were collected at five sites in the Colorado River tailwater of Glen Canyon Dam to document the daily, seasonal, and longitudinal range of variation in water chemistry that could occur annually within the Glen Canyon reach.
Arizona↗
Sampling and analysis plan for the Koocanusa Reservoir and upper Kootenai River, Montana, water-quality monitoring program, 2021
In 2021, the U.S. Geological Survey will collect water-quality samples and environmental data from 3 sites in Koocanusa Reservoir and from 1 site in the Kootenai River. The transboundary Koocanusa Reservoir is in southeastern British Columbia, Canada, and northwestern Montana, United States, and was formed with the construction of Libby Dam on the Kootenai River 26 kilometers upstream from Libby, Montana. Two of the reservoir sites and the Kootenai River site, in the Libby Dam tailwater (the outflow of the reservoir flow into the Kootenai River), are equipped with automated, high-frequency ServoSipper water samplers. At the two reservoir sites, these samplers are mounted to pontoon platforms and automatically collect samples from multiple depths; a ServoSipper sampler was deployed at one site in 2019, and another ServoSipper sampler will be deployed at a second site in 2021. Discrete water-quality samples will be collected monthly at two depths at the river site and at two of the reservoir sites. The goal of this project is to collect multidepth, high-frequency vertical and temporal water-quality samples and data to understand the limnological and biological processes that control variations and trends in selenium concentrations and loads throughout Koocanusa Reservoir and in the Libby Dam tailwater at the southern end of the reservoir. This sampling and analysis plan documents the organization, sampling and data-collection scheme and design, pre- and post-collection processes, and quality-assurance and quality-control procedures.
Montana↗
Sampling and analysis plan for the water-quality monitoring program in Lake Koocanusa and upper Kootenai River, Montana, water years 2022–23
The U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, collected water-quality samples and environmental data in Lake Koocanusa (also known as “Koocanusa Reservoir”), the Kootenai River, and the Tobacco River during water years 2022–23. The transboundary Lake Koocanusa is in southeastern British Columbia, Canada, and northwestern Montana, United States. It was formed by constructing Libby Dam on the Kootenai River 26 kilometers upstream from Libby, Montana. One of the lake sites and the Kootenai River site, in the Libby Dam tailwater (the outflow of the lake flow into the Kootenai River), were equipped with automated, high-frequency ServoSipper water samplers. At the lake site, these samplers were mounted to pontoon platforms during the summer, and a submersible ServoSipper sipper was deployed with ice buoys during the winter. Samples were automatically collected from multiple depths. At the Kootenai River site, these samplers were housed in the gage house. In water year 2022, discrete water-quality samples were collected every 4–6 weeks, year round, at all four lake sites in the Kootenai River between April and November. In water year 2023, discrete water-quality samples were collected at three lake sites and the Kootenai and Tobacco River sites every 4–6 weeks. The goal of this project was to collect multidepth, high-frequency vertical and temporal water-quality samples and data to understand the limnological and biological processes that control variations and trends in selenium concentrations and loads throughout Lake Koocanusa and in the Libby Dam tailwater at the southern end of the lake. This sampling and analysis plan documents the organization, sampling and data-collection scheme and design, pre- and post-collection processes, and quality-assurance and quality-control procedures of the Koocanusa/Kootenai water-quality monitoring program during water years 2022–23.
Montana↗
Plan of study to determine if the isotopic ratios [delta]15 N and [delta]18 O can reveal the sources of nitrate discharged by the Mississippi River into the Gulf of Mexico
Nitrate and other nutrients discharged from the Mississippi River basin are suspected of causing a zone of depleted dissolved oxygen (hypoxic zone) in the Gulf of Mexico each summer. The hypoxic zone may have an adverse effect on aquatic life and commercial fisheries. Commercial fertilizers are the dominant source of nitrogen input to the Mississippi basin. Other nitrogen sources include animal waste, fixation of atmospheric nitrogen by legumes, precipitation, domestic and industrial effluent, and the soil. The inputs of nitrogen from most of these sources to the Mississippi basin can be estimated and the outputs in surface water can be measured. However, nitrogen from each source is affected differently by physical, chemical, and biological processes that control nitrogen cycling in terrestrial and aquatic systems. Hence, the relative contributions from the various sources of nitrogen to nitrate load in the Mississippi River are unknown because the different sources may not contribute proportionally to their inputs in the basin. It may be possible to determine the relative contributions of the major sources of nitrate in river water using the stable isotopic ratios d15N and d18O of the nitrate ion. A few researchers have used the d15N and/or d18O isotope ratios to determine sources of nitrate in ground water, headwater catchments, and small rivers, but little is known about the isotopic composition of nitrate in larger rivers. The objective of this study is to measure the isotopic composition of nitrate and suspended organic matter in the Mississippi River and its major tributaries, in discharge to the Gulf of Mexico, and in streamflow from smaller watersheds that have distinct sources of nitrogen (row crops, animal wastes, and urban effluents) or are minimally impacted by man (undeveloped). Samples from seven sites on the Mississippi River and its tributaries and from 17 sites in smaller watersheds within the Mississippi River basin will be analyzed for d15N and d18O of dissolved nitrate. Suspended sediment collected from these sites will also be analyzed to determine the d15N, d13C, and d34S of the suspended organic material. Six samples will be collected at each site during the winter, spring, and summer of 1996-97. Results from these samples will be used to identify seasonal and flow-related variability in d15N and d18O ratios from each site and may also help determine the principal sources of the nitrate entering the Gulf of Mexico.
Open-File Report↗
Geologic map of the Cameron 30' x 60' quadrangle, Coconino County, northern Arizona
This geologic map is the result of a cooperative effort of the U.S. Geological Survey and the National Park Service in collaboration with the Navajo Nation and the Hopi Tribe to provide regional geologic information for resource management officials of the National Park Service, U.S. Forest Service, Navajo Indian Reservation (herein the Navajo Nation), the Hopi Tribe, and for visitor information services at Grand Canyon National Park, Arizona as well as private enterprises that have lands within the area. The Cameron 30’ x 60’ quadrangle encompasses approximately 5,018 km 2 (1,960 mi 2 ) within Coconino County, northern Arizona and is bounded by longitude 111° to 112° W., and latitude 35°30’ to 36° N. The map area is within the southern Colorado Plateaus geologic province (herein Colorado Plateau). The map area is locally subdivided into six physiographic areas: the Grand Canyon (including the Little Colorado River Gorge), Coconino Plateau, Marble Plateau, Little Colorado River Valley, Moenkopi Plateau, and the San Francisco Volcanic Field as defined by Billingsley and others, 1997 (fig. 1). Elevations range from about 2,274 m (7,460 ft) at the south rim of Grand Canyon along State Highway 64 to about 994 m (3,260 ft) in the Grand Canyon, northeast quarter of the map area. The Cameron quadrangle is one of the few remaining areas near the Grand Canyon where uniform geologic mapping was needed for geologic connectivity of the regional geologic framework that will be useful to federal, state, and private land resource managers who direct environmental and land management programs such as range management, biological studies, flood control, and water resource investigations. The geologic information presented will support future and ongoing local geologic investigations and associated scientific studies of all disciplines within the Cameron quadrangle area.
Arizona↗
Geologic Map of the House Rock Valley Area, Coconino County, Northern Arizona
This geologic map is a cooperative effort of the U.S. Geological Survey (USGS), the Bureau of Land Management, the National Park Service, and the U.S. Forest Service to provide a geologic database for resource management officials and visitor information services. This map was produced in response to information needs related to a proposed withdrawal of three segregated land areas near Grand Canyon National Park, Arizona, from new hard rock mining activity. House Rock Valley was designated as the east parcel of the segregated lands near the Grand Canyon. This map was needed to provide connectivity for the geologic framework of the Grand Canyon segregated land areas. This geologic map of the House Rock Valley area encompasses approximately 280 mi2 (85.4 km2) within Coconino County, northern Arizona, and is bounded by longitude 111 degrees 37'30' to 112 degrees 05' W. and latitude 36 degrees 30' to 36 degrees 50' N. The map area is in the eastern part of the Arizona Strip, which lies within the southern Colorado Plateaus geologic province (herein Colorado Plateau). The Arizona Strip is the part of Arizona lying north of the Colorado River. The map is bound on the east by the Colorado River in Marble Canyon within Grand Canyon National Park and Glen Canyon National Recreation Area, on the south and west by the Kaibab National Forest and Grand Canyon National Game Preserve, and on the north by the Vermilion Cliffs Natural Area, the Paria Canyon Vermilion Cliffs Wilderness Area, and the Vermilion Cliffs National Monument. House Rock State Buffalo Ranch also bounds the southern edge of the map area. The Bureau of Land Management Arizona Field Office in St. George, Utah, manages public lands of the Vermilion Cliffs Natural Area, Paria Canyon - Vermilion Cliffs Wilderness and Vermilion Cliffs National Monument. The North Kaibab Ranger District in Fredonia, Arizona, manages U.S. Forest Service land along the west edge of the map area and House Rock State Buffalo Ranch. Other lands include about 13 sections of Arizona State land, about ? of a section of private land along House Rock Wash, and about 1? sections of private land at Cliff Dwellers Lodge, Vermilion Cliffs Lodge, and Marble Canyon, Arizona. Landmark features within the map area include the Vermilion Cliffs, Paria Plateau, Marble Canyon, and House Rock Valley. Surface drainage in House Rock Valley is to the east toward the Colorado River in Marble Canyon. Large tributaries of Marble Canyon from north to south include Badger Canyon, Soap Creek, Rider Canyon, North Canyon, Bedrock Canyon, and South Canyon. Elevations range from about 2,875 ft (876 m) at the Colorado River in the southeast corner of the map to approximately 7,355 ft (2,224 m) on the east rim of Paria Plateau along the north-central edge of the map area. Three small settlements are in the map area along U.S. Highway 89A, Cliff Dwellers Lodge, Vermilion Cliffs Lodge, and Marble Canyon, Arizona. The community of Jacob Lake is about 9 mi (14.5 km) west of House Rock Valley on the Kaibab Plateau. Lees Ferry is 5 mi (8 km) north of Marble Canyon and marks the confluence of the Paria and Colorado Rivers and the beginning of Marble Canyon. U.S. Highway 89A provides access to the northern part of the map area. Dirt roads lead south into House Rock Valley from U.S. Highway 89A and are collectively maintained by the Bureau of Land Management, the U.S. National Forest Service, and the Grand Canyon Trust. House Rock Valley is one of the few remaining areas where uniform geologic mapping is needed for connectivity to the regional Grand Canyon geologic framework. This information is useful to Federal and State resource managers who direct environmental and land management programs that encompass such issues as range management, biological studies, flood control, water, and mineral-resource investigations. The geologic information will support future and ongoing geologic investigations and scientific studies
Scientific Investigations Map↗