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At least 523 records · Page 29Linked to original sources

USGS2016

Ancient DNA reveals substantial genetic diversity in the California Condor ( Gymnogyps californianus ) prior to a population bottleneck

Critically endangered species that have undergone severe population bottlenecks often have little remaining genetic variation, making it difficult to reconstruct population histories to apply in reintroduction and recovery strategies. By using ancient DNA techniques, it is possible to combine genetic evidence from the historical population with contemporary samples to provide a more complete picture of a species' genetic variation across its historical range and through time. Applying this approach, we examined changes in the mitochondrial DNA (mtDNA) control region (526 base pairs) of the endangered California Condor ( Gymnogyps californianus ). Results showed a >80% reduction in unique haplotypes over the past 2 centuries. We found no spatial sorting of haplotypes in the historical population; the periphery of the range contained haplotypes that were common throughout the historical range. Direct examination of mtDNA from California Condor museum specimens provided a new window into historical population connectivity and genetic diversity showing: (1) a substantial loss of haplotypes, which is consistent with the hypothesis that condors were relatively abundant in the nineteenth century, but declined rapidly as a result of human-caused mortality; and (2) no evidence of historical population segregation, meaning that the available genetic data offer no cause to avoid releasing condors in unoccupied portions of their historical range.

The Condor↗

USGS1999

Exotic plant species invade hot spots of native plant diversity

Some theories and experimental studies suggest that areas of low plant species richness may be invaded more easily than areas of high plant species richness. We gathered nested-scale vegetation data on plant species richness, foliar cover, and frequency from 200 1-m 2 subplots (20 1000-m 2 modified-Whittaker plots) in the Colorado Rockies (USA), and 160 1-m 2 subplots (16 1000-m 2 plots) in the Central Grasslands in Colorado, Wyoming, South Dakota, and Minnesota (USA) to test the generality of this paradigm. At the 1-m 2 scale, the paradigm was supported in four prairie types in the Central Grasslands, where exotic species richness declined with increasing plant species richness and cover. At the 1-m 2 scale, five forest and meadow vegetation types in the Colorado Rockies contradicted the paradigm; exotic species richness increased with native-plant species richness and foliar cover. At the 1000-m 2 plot scale (among vegetation types), 83% of the variance in exotic species richness in the Central Grasslands was explained by the total percentage of nitrogen in the soil and the cover of native plant species. In the Colorado Rockies, 69% of the variance in exotic species richness in 1000-m 2 plots was explained by the number of native plant species and the total percentage of soil carbon. At landscape and biome scales, exotic species primarily invaded areas of high species richness in the four Central Grasslands sites and in the five Colorado Rockies vegetation types. For the nine vegetation types in both biomes, exotic species cover was positively correlated with mean foliar cover, mean soil percentage N, and the total number of exotic species. These patterns of invasibility depend on spatial scale, biome and vegetation type, spatial autocorrelation effects, availability of resources, and species-specific responses to grazing and other disturbances. We conclude that: (1) sites high in herbaceous foliar cover and soil fertility, and hot spots of plant diversity (and biodiversity), are invasible in many landscapes; and (2) this pattern may be more closely related to the degree resources are available in native plant communities, independent of species richness. Exotic plant invasions in rare habitats and distinctive plant communities pose a significant challenge to land managers and conservation biologists.

Ecological Monographs↗

USGS2013

Significance of exchanging SSURGO and STATSGO data when modeling hydrology in diverse physiographic terranes

The Water Availability Tool for Environmental Resources (WATER) is a TOPMODEL-based hydrologic model that depends on spatially accurate soils data to function in diverse terranes. In Kentucky, this includes mountainous regions, karstic plateau, and alluvial plains. Soils data are critical because they quantify the space to store water, as well as how water moves through the soil to the stream during storm events. We compared how the model performs using two different sources of soils data--Soil Survey Geographic Database (SSURGO) and State Soil Geographic Database laboratory data (STATSGO)--for 21 basins ranging in size from 17 to 1564 km 2 . Model results were consistently better when SSURGO data were used, likely due to the higher field capacity, porosity, and available-water holding capacity, which cause the model to store more soil-water in the landscape and improve streamflow estimates for both low- and high-flow conditions. In addition, there were significant differences in the conductivity multiplier and scaling parameter values that describe how water moves vertically and laterally, respectively, as quantified by TOPMODEL. We also evaluated whether partitioning areas that drain to streams via sinkholes in karstic basins as separate hydrologic modeling units (HMUs) improved model performance. There were significant differences between HMUs in properties that control soil-water storage in the model, although the effect of partitioning these HMUs on streamflow simulation was inconclusive.

Kentucky↗

USGS2012

Diversity and distribution of mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera) of the South Platte River Basin, Colorado, Nebraska, and Wyoming, 1873-2010

The U.S. Geological Survey, in cooperation with the C.P. Gillette Museum of Arthropod Diversity (Colorado State University, Fort Collins, Colorado), compiled collection record data to document the historical and present-day occurrence of mayfly, stonefly, and caddisfly species in the South Platte River Basin. Data were compiled from records collected between 1873 and 2010 to identify where regional knowledge about species occurrence in the basin is lacking and to encourage future researchers to locate additional populations of these poorly understood but very important organisms. This report provides a description of how data were compiled, a map of approximate collection locations, a listing of the most recent collection records from unique locations, general remarks for each species, a species list with selected summary information, and distribution maps of species collection records.

Colorado;Nebraska;Wyoming↗

USGS2014

Invasive lionfish use a diversity of habitats in Florida

Two species of lionfish ( Pterois volitans and Pterois miles ) are the first marine fishes known to invade and establish self-sustaining populations along the eastern seaboard of the United States. First documented off the coast of Florida in 1985, lionfish are now found along the Atlantic coast of the United States as well as in the Caribbean Sea and Gulf of Mexico. Although long-term effects of this invasion are not yet fully known, there is early evidence that lionfish are negatively impacting native marine life. The lionfish invasion raises questions about which types of habitat the species will occupy in its newly invaded ecosystem. In their native range, lionfish are found primarily on coral reefs but sometimes are found in other habitats such as seagrasses and mangroves. This fact sheet documents the diversity of habitat types in which invasive lionfish have been reported within Florida’s coastal waters, based on lionfish sightings recorded in the U.S. Geological Survey Nonindigenous Aquatic Species database (USGS-NAS).

Florida↗

USGS2009

Recent subsidence and erosion at diverse wetland sites in the southeastern Mississippi Delta Plain

A prior study (U.S. Geological Survey Open-File Report 2005-1216) examined historical land- and water-area changes and estimated magnitudes of land subsidence and erosion at five wetland sites in the Terrebonne hydrologic basin of the Mississippi delta plain. The present study extends that work by analyzing interior wetland loss and relative magnitudes of subsidence and erosion at five additional wetland sites in the adjacent Barataria hydrologic basin. The Barataria basin sites were selected for their diverse physical settings and their recent (post-1978) conversion from marsh to open water. Historical aerial photography, datum-corrected marsh elevations and water depths, sediment cores, and radiocarbon dates were integrated to evaluate land-water changes in the Mississippi delta plain on both historical and geological time scales. The thickness of the organic-rich sediments (peat) and the elevation of the stratigraphic contact between peat and underlying mud were compared at marsh and open-water sites across areas of formerly continuous marsh to estimate magnitudes of recent delta-plain elevation loss caused by vertical erosion and subsidence of the wetlands. Results of these analyses indicate that erosion exceeded subsidence at most of the study areas, although both processes have contributed to historical wetland loss. Comparison of these results with prior studies indicates that subsidence largely caused rapid interior wetland loss in the Terrebonne basin before 1978, whereas erosional processes primarily caused more gradual interior wetland loss in the Barataria basin after 1978. Decadal variations in rates of relative sea-level rise at a National Ocean Service tide gage, elevation changes between repeat benchmark-leveling surveys, and GPS height monitoring at three National Geodetic Survey Continuously Operating Reference Stations indicate that subsidence rates since the early 1990s are substantially lower than those previously reported and are similar in magnitude to time-averaged subsidence rates at geological time scales. The historical decrease in land-loss rates across the Mississippi delta plain generally is consistent with the recent decrease in subsidence rates within the same region.

Louisiana↗

USGS2009

Young Stand Thinning and Diversity Study: Response of Songbird Community One Decade Post-Treatment

The response of songbird assemblages to commercial thinning is likely to change as vegetation develops over time after thinning. The influence of thinning intensity and pattern on the timing of transitions in bird community composition following thinning is of interest to managers when a goal is to maintain diversity and accelerate the development of late-seral forest structure. We investigated changes in the composition of songbird assemblages and density of individual species from 2 years before to 12 years after experimental thinning of 40-year-old stands dominated by Douglas-fir (Pseudotsuga menziesii) in the Oregon Cascades. Species richness, and density for five species and the neotropical migrant group were greater in thinned than in unthinned control stands over all post-treatment years of the study. Similarly, three species maintained a negative response to thinning over the post-treatment period. The initial positive influence of thinning was no longer in evidence a decade after harvest for five species. Of seven species with an initial negative response to thinning, three indicated recovery towards pre-treatment densities by the end of the most recent post-treatment survey. Our study is one of the first to document long-term effects of commercial thinning on forest songbird assemblages in the Pacific Northwest.

Open-File Report↗

USGS2011

Habitat diversity in the Northeastern Gulf of Mexico: Selected video clips from the Gulfstream Natural Gas Pipeline digital archive

This project combines underwater video with maps and descriptions to illustrate diverse seafloor habitats from Tampa Bay, Florida, to Mobile Bay, Alabama. A swath of seafloor was surveyed with underwater video to 100 meters (m) water depth in 1999 and 2000 as part of the Gulfstream Natural Gas System Survey. The U.S. Geological Survey (USGS) in St. Petersburg, Florida, in cooperation with Eckerd College and the Florida Department of Environmental Protection (FDEP), produced an archive of analog-to-digital underwater movies. Representative clips of seafloor habitats were selected from hundreds of hours of underwater footage. The locations of video clips were mapped to show the distribution of habitat and habitat transitions. The numerous benthic habitats in the northeastern Gulf of Mexico play a vital role in the region's economy, providing essential resources for tourism, natural gas, recreational water sports (fishing, boating, scuba diving), materials, fresh food, energy, a source of sand for beach renourishment, and more. These submerged natural resources are important to the economy but are often invisible to the general public. This product provides a glimpse of the seafloor with sample underwater video, maps, and habitat descriptions. It was developed to depict the range and location of seafloor habitats in the region but is limited by depth and by the survey track. It should not be viewed as comprehensive, but rather as a point of departure for inquiries and appreciation of marine resources and seafloor habitats. Further information is provided in the Resources section.

Florida;Alabama;Mississippi;Louisiana↗

USGS2012

The role of the U.S. Geological Survey in Lake Michigan Diversion Accounting in Illinois, 1984-2010

The State of Illinois' annual withdrawl from Lake Michigan is limited by a U.S. Supreme Court decree. The U.S. Geological Survey (USGS) is responsible for monitoring flows in the Chicago area waterway system (CAWS) as part of the Lake Michigan Diversion Accounting (LMDA) overseen by the U.S. Army Corps of Engineers, Chicago District. Every five years, the USGS streamgage practices in the CAWS are reviewed by a committee of practicing engineers and academics to ensure that the best engineering practices are implemented in accordance with the U.S. Supreme Court decree and as part of LMDA. This report provides a perspective on the role of the USGS in LMDA from 1984 to 2010 including the responses to the review committees. Six technical review committees have been convened by the U.S. Corps of Engineers to evaluate the key components of LMDA especially the USGS streamgages within the CAWS. Any changes in streamgaging practices at CAWS gaging stations require detailed analysis to ensure the change will not adversely affect the ability of the USGS to accurately monitor flows.

Illinois↗

USGS1954

Diversions from Red River to Lake Dallas, Texas; and related channel losses, February and March 1954

During the period Feb. 10 to Mar. 3, 19541 the City of Dallas pumped 1,363 acre-feet of water from its Red River plant into Pecan Creek (a tributary of Elm Fork Trinity River) 3.5 miles above Gainesville; 1,272 acre-feet of this diversion reached the head of Lake Dallas. Discharge records were obtained at four points along the channels. This water was transported down the channels of Pecan Creek and Elm Fork Trinity River to Lake Dallas, a distance of about 31 miles.

Texas↗

USGS1966

Effect of treated effluent diversion on Yahara River flow, Wisconsin

Before December 1958 the treated sewage effluent from the Madison, Wisconsin, metropolitan area was discharged into the Yahara River at the north end of Lake Waubesa, which is upstream from the USGS gaging station on the Yahara River near McFarland, Wis. Since December 1958 the effluent has been diverted southward from the sewage treatment plant into Badfish Creek and enters the lower reach of Yahara River, thus byrpassing the gaging station. The purpose of this report is to demonstrate the effect that this diversion seems to have on the flow of the Yahara River near McFarland. Indirectly, it also demonstrates the effect on streamflow of withdrawing ground water for use in the Madison metropolitan area since the treated effluent is primarily the major portion of the used ground water.

Wisconsin↗

USGS1977

Development of water facilities in the Santa Ana River Basin, California, 1810-1968: a compilation of historical notes derived from many sources describing ditch and canal companies, diversions, and water rights

This report traces by text, maps, and photographs, the development of the water supply in the Santa Ana River basin from its beginning in 1810 or 1811 to 1968. The value of the report lies in the fact that interpretation of the hydrologic systems in the basin requires knowledge of the concurrent state of development of the water supply, because that development has progressively altered the local regimen of both surface water and ground water. Most of the information for the earlier years was extracted and condensed from an investigation made by W. H. Hall, California State Engineer during the years 1878-87. Hall's study described irrigation development in southern California from its beginning through 1888. Information for the years following 1888 was obtained from the archives of the numerous water companies and water agencies in the Santa Ana River basin and from the various depositories of courthouse, county, and municipal records. The history of water-resources development in the Santa Ana River basin begins with the introduction of irrigation in the area by the Spanish, who settled in southern California in the latter part, of the 18th century. The first irrigation diversion from the Santa Ana River was made in 1810 or 1811 by Jose Antonio Yorba and Juan Pablo Peralta. Irrigation remained a localized practice during the Mexican-Californian, or rancho, period following the separation of Mexico from Spain in 1821. Rancho grantees principally raised cattle, horses, and sheep and irrigated only small· plots of feed grain for their livestock and fruit crops for household use. The breakup of the ranchos through sales to Americans, who were migrating to California in ever-increasing numbers following the acquisition of California by the United States in 1848, marked the beginning of a rapid increase in water use and the beginning of widespread irrigation. Many water companies and water agencies were organized to divert the surface flow of the Santa Ana River and its tributaries for irrigation. The Santa Ana River had been a perennial stream, except in years of extreme drought, from its source in the mountains nearly to the Pacific Ocean. With the great increase in population and the accompanying use of water for irrigation, the river was no longer a perennial stream, and it was necessary to supplement the surface-water supply with ground water. Many wells were dug or drilled in the artesian areas of the upper basin; of those wells many originally flowed, but as ground-water pressures and levels declined, an increasing amount of pumping was required. Conservation measures were taken to store some of the surplus winter runoff for use during low runoff years and during summer periods of heavy demand. Conservation facilities included surface-storage reservoirs and water-spreading grounds or percolation basins for utilization of underground storage. The competition for water in the Santa Ana River basin has been accompanied by frequent litigation over water tights, and over the years these water rights have generally been established by court decree. Although the demand for water still increases, the water demand for agricultural use has declined since the mid-1940's in response to the rapid urbanization of agricultural areas. Since that date the continued expansion of communities has encroached significantly into the agricultural areas causing a decrease in water use for agriculture, a more than compensating increase in water use for municipal purposes, and a rapid change in the ownership of water rights. The urbanization of flood plains made floods potentially more damaging than they previously had been when the flood plains were used for agriculture. In recognition of this increased hazard, flood-control facilities such as reservoirs, debris basins, flood-conveyance channels, and levees have been constructed to reduce potential damage. Most of the construction has occurred since the devastating flood of March 1938. By the mid-1940's it was apparent that the local water supply--both surface and ground water--would be insufficient to meet the increasing demand in the basin. To augment the local supply, Colorado River water was purchased from the Metropolitan Water District of Southern California and released to the Santa Ana River beginning in August 1949. Additional supplemental water became available in the early 1970's from northern California through the conveyance facilities of the California Water Project.

California↗

USGS2006

Computation and error analysis of discharge for the Lake Michigan Diversion Project in Illinois: 1997-99 water years

Acoustic velocity meters (AVM's) and acoustic Doppler current profilers (ADCP's) were used to measure streamflow at four streamflow-gaging stations in the Chicago River system. The streamflow data were used to compute discharge and to determine the uncertainty in the computed annual mean discharge at each station for the Lake Michigan Diversion Project in Illinois. Descriptions of the instrumentation at each station, stage-area and index-velocity ratings, and methods utilized for computing discharge and estimating missing record are given. Daily mean and annual mean discharges were computed for each station for 1997-99 water years (WY's). A water year is defined as the 12-month period from October 1 through September 30. The water year is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus, the year ending September 30, 1999, is called the 1999 water year. A first-order error analysis was applied to acoustic velocity meter (AVM) data, stage-area, and index-velocity ratings at each streamflow-gaging station. The error analysis results indicate that the uncertainty is sensitive to the value of uncertainty associated with acoustic Doppler cur-rent profiler (ADCP) discharge measurement data. At the Chicago River at Columbus Drive at Chicago, Illinois station for the 1997-99 WY's, the uncertainty, expressed as a standard deviation of the average annual discharge, ranged from 13 to 18 cubic feet per second (ft3/s) when ADCP uncertainty was not included, whereas total uncertainty ranged from 55 to 69 ft3/s when ADCP uncertainty was included. At the Chicago Sanitary and Ship Canal at Romeoville, Illinois station for the 1997-99 WY's, the uncertainty ranged from 18 to 20 ft3/s when ADCP uncertainty was not included, whereas it ranged from 64 to 68 ft3/s when it was included. At the Calumet River below O'Brien Lock and Dam at Chicago, Illinois station for the 1997-99 WY's, the uncertainty ranged from 13 to 22 ft3/s when ADCP uncertainty was not included, whereas it ranged from 35 to 53 ft3/s when it was included. At the North Shore Channel at Wilmette, Illinois station for the 1997-99 WY's, when the record was entirely estimated, the uncertainty ranged from 8 to 12 ft3/s when the ADCP uncertainty was not included, and from 16 to 17 ft3/s when it was included. For the 2000 WY, the estimated uncertainty was 8.6 ft3/s when ADCP uncertainty is not included and 12.5 ft3/s when ADCP uncertainty was included.

Illinois↗

USGS2015

Analysis of regional rainfall-runoff parameters for the Lake Michigan Diversion hydrological modeling

The Lake Michigan Diversion Accounting (LMDA) system has been developed by the U.S. Army Corps of Engineers, Chicago District (USACE-Chicago) and the State of Illinois as a part of the interstate Great Lakes water regulatory program. The diverted Lake Michigan watershed is a 673-square-mile watershed that is comprised of the Chicago River and Calumet River watersheds. They originally drained into Lake Michigan, but now flow to the Mississippi River watershed via three canals constructed in the Chicago area in the early twentieth century. Approximately 393 square miles of the diverted watershed is ungaged, and the runoff from the ungaged portion of the diverted watershed has been estimated by the USACE-Chicago using the Hydrological Simulation Program-FORTRAN (HSPF) program. The accuracy of simulated runoff depends on the accuracy of the parameter set used in the HSPF program. Nine parameter sets comprised of the North Branch, Little Calumet, Des Plaines, Hickory Creek, CSSC, NIPC, 1999, CTE, and 2008 have been developed at different time periods and used by the USACE-Chicago. In this study, the U.S. Geological Survey and the USACE-Chicago collaboratively analyzed the parameter sets using nine gaged watersheds in or adjacent to the diverted watershed to assess the predictive accuracies of selected parameter sets. Six of the parameter sets, comprising North Branch, Hickory Creek, NIPC, 1999, CTE, and 2008, were applied to the nine gaged watersheds for evaluating their simulation accuracy from water years 1996 to 2011. The nine gaged watersheds were modeled by using the three LMDA land-cover types (grass, forest, and hydraulically connected imperviousness) based on the 2006 National Land Cover Database, and the latest meteorological and precipitation data consistent with the current (2014) LMDA modeling framework. Results indicate that the North Branch and Hickory Creek parameter sets, which belong to the original calibration group, attained an overall “satisfactory” rating on monthly runoff volumes based on the three performance statistics selected, but the annual and over-the-period runoff volumes were generally underestimated. Parameter sets CTE and 2008 attained a similar satisfactory rating on monthly runoff volumes but the annual and over-the-period runoff volumes were overestimated in general. Although the percent bias was improved, the CTE and 2008 parameter sets also had increased residuals in monthly runoff volumes and decreased quality of the model fit to the measured streamflows relative to the North Branch and Hickory Creek parameter sets. The NIPC and 1999 parameter sets, on the other hand, had larger percent bias and residuals in monthly runoff volumes, and underestimated the annual and over-the-period runoff volumes. Recalibration of the HSPF parameters to the updated inputs and land covers was completed on two representative watershed models selected from the nine by using a manual method (HSPEXP) and an automatic method (PEST). The objective of the recalibration was to develop a regional parameter set that improves the accuracy in runoff volume prediction for the nine study watersheds. Knowledge about flow and watershed characteristics plays a vital role for validating the calibration in both manual and automatic methods. The best performing parameter set was determined by the automatic calibration method on a two-watershed model. Applying this newly determined parameter set to the nine watersheds for runoff volume simulation resulted in “very good” ratings in five watersheds, an improvement as compared to “very good” ratings achieved for three watersheds by the North Branch parameter set.

Illinois, Indiana↗

USGS2020

Temperature and water-quality diversity and the effects of surface-water connection in off-channel features of the Willamette River, Oregon, 2015–16

Water-quality conditions (including temperature) in the Willamette River and many of its adjacent off-channel features, such as alcoves and side channels, were monitored between river miles 67 (near Salem, Oregon) and 168 (near Eugene, Oregon) during the summers of 2015 and 2016. One or more parameters (water temperature, dissolved oxygen, pH, specific conductance, and [or] water depth) were continuously measured at sites in the main channel (9 sites in 2015; 5 sites in 2016) and select off-channel features (20 features in 2015; 22 features in 2016). This study was initiated in reaction to the unusually warm, dry weather and resulting low streamflows that occurred in the Pacific Northwest in 2015 and the need for flow managers to understand the effects of streamflow on water-quality conditions in off-channel features of the Willamette River. Field monitoring was focused on documenting water-quality conditions during low summer streamflows and during fluctuations in streamflow, including when side channels became alcoves and reconnected to become side channels again. Water in the main channel of the Willamette River upstream from river mile 50 near Newberg typically is well mixed during summer, with warm water temperatures (greater than 18 degrees Celsius) and high dissolved-oxygen concentrations (often greater than 7.7 milligrams per liter). During low summer flows, a diverse suite of off-channel features exists adjacent to the main channel of the Willamette River. Despite temporal and spatial variability within individual features, comparison of continuous water-temperature data between the main channel and off-channel features indicated that some off-channel features were consistently cooler than the main channel, some were consistently warmer than the main channel, and others frequently fluctuated between warmer or cooler than the main channel. Site-specific characteristics including upstream connection, depth, and presence or absence of aquatic or riparian vegetation were factors that seemed to affect the water quality of a feature. Results from this study showed a relation between the geomorphology, hydrology, ecology, and water quality of an off-channel feature. Data confirmed that many features that can be classified as cold-water refuges based on water-temperature standards also contained low concentrations of dissolved oxygen that may not be suitable for sensitive fish species. A simplified site classification scheme is proposed that links water-quality conditions in measured off-channel features with site-specific characteristics and summer streamflows. The site classification scheme was extended to create a theoretical process matrix that relates measured water-quality conditions to a list of the processes and site-specific characteristics that could create those conditions.

Oregon↗

USGS2000

Stormflow chemistry in the Santa Ana River below Prado Dam and at the diversion downstream from Imperial Highway, southern California, 1995-98

The Santa Ana River drains about 2,670 square miles of the densely populated coastal area of southern California, near Los Angeles. Almost all the flow in the river, more than 200,000 acre-feet annually, is diverted into ponds where it infiltrates and recharges underlying aquifers. About 2 million people are dependent on these aquifers for water supply. Stormflow in the Santa Ana River is considered a source of "high-quality" water suitable for use as a source of ground-water recharge. To test this assumption, stormflow samples were collected at two locations--below Prado Dam and at the diversion point downstream from Imperial Highway--for 12 winter storms between 1995 and 1998. Nitrate concentrations decreased during stormflow from a median concentration of 7.8 milligrams per liter in base flow to concentrations less than 1 milligram per liter in some large storms. Concentrations of chemically reduced forms of nitrogen (nitrite, ammonia, and organic nitrogen) increased during stormflow and are the predominant forms of nitrogen in large stormflows. Dissolved organic carbon (DOC) concentrations increased from a median concentration of 4.6 milligrams per liter in base flow to more than 20 milligrams per liter in some stormflows. Concentrations of DOC were especially high during the first storm of the rainy season, and large increases in DOC concentrations were measured even as a result of small early season storms that did not cause large increases in streamflow. DOC present during early season stormflow had less ultraviolet absorbance at 254 nanometers (UV 254 ) per unit of carbon than did DOC from late season stormflows. DOC in water held in storage behind Prado Dam had the highest UV 254 absorbance per unit of carbon. Maximum pesticide concentrations in stormflow did not exceed U.S. Environmental Protection Agency Maximum Contaminant Levels. Most pesticide concentrations were less than 1 microgram per liter and less than the detection limits obtained using standard drinking water analyses. Increases in concentrations of pesticides such as diazinon, malathion, and chlorpyrifos in stormflow result from runoff from urban areas downstream from Prado Dam. In general, large late season stormflows have the most pesticide detections of all stormflows sampled. Concentrations of methyl tert-butyl ether (MTBE), a gasoline additive, during base flow were as high as 0.9 microgram per liter and concentrations decreased during stormflow. Like pesticides, the concentrations did not exceed the U.S. Environmental Protection Agency Maximum Contaminant Levels for MTBE.

California↗

USGS1996

Arsenic and selenium in soils and shallow ground water in the Turtle Lake, New Rockford, Harvey Pumping, Lincoln Valley, and LaMoure irrigation areas of the Garrison Diversion Unit, North Dakota

The Garrison Diversion Unit project was authorized as part of the Pick-Sloan Missouri River Basin program to divert water from Lake Sakakawea to irrigation areas in North Dakota. A special Garrison Commission was created to evaluate an environmental concern that return flow from the irrigation areas might contain metals in toxic concentrations. This report summarizes the results of detailed investigations of the Turtle Lake, New Rockford, Harvey Pumping, Lincoln Valley, and LaMoure irrigation areas. A total of 223 soil samples were collected from the irrigation areas and analyzed for elemental composition. Water extractions were done on 40 of the 223 soil samples using a 1:5 soil-to-water extraction method, and the solution from the extraction was analyzed for elemental composition. A total of 52 ground-water samples were collected and analyzed for inorganic constituents and organic carbon. Average arsenic concentrations in the entire soil column ranged from 1.0 milligram per kilogram in the Harvey Pumping irrigation area to 70 milligrams per kilogram in the New Rockford irrigation area. Average selenium concentrations ranged from less than 0.1 milligram per kilogram in the Turtle Lake, New Rockford, Harvey Pumping, and Lincoln Valley irrigation areas to 6.0 milligrams per kilogram in the Turtle Lake irrigation area. In the Turtle Lake irrigation area, average arsenic and selenium concentrations generally increased with depth through the topsoil, oxidized soil, and transition soil but decreased in the reduced soil at the bottom of the sampled horizons. Average arsenic concentrations in the New Rockford irrigation area follow the same pattern as in the Turtle Lake irrigation area, but selenium concentrations do not show a clear pattern of variation with depth. In the Harvey Pumping and Lincoln Valley irrigation areas, arsenic and selenium concentrations do not appear to vary systematically with depth. No correlation is shown between the concentrations in soils and soil extracts, indicating that, based on conditions of laboratory soil-water extraction experiments, trace-element concentrations in soils are not good predictors of trace-element concentrations in irrigation return flow. Arsenic concentrations in the aquifers ranged from less than 1 microgram per liter to 27 micrograms per liter. Arsenic concentrations generally were larger in the deep part of the aquifers underlying the Turtle Lake and New Rockford irrigation areas than in the shallow part of the aquifers. In the shallow part of the aquifers, where oxidizing conditions prevail, arsenic is strongly adsorbed to soil particles. In the deep part of the aquifers, where reducing conditions prevail, arsenic is more mobile. Selenium concentrations in the aquifers ranged from less than 1 microgram per liter to 4 micrograms per liter. Little difference existed between the selenium concentrations in the shallow part of the aquifers underlying the irrigation areas and the concentrations in the deep part of the aquifers.

Water-Resources Investigations Report↗

USGS2014

Microbial aggregates within tissues infect a diversity of corals throughout the Indo-Pacific

Coral reefs are highly diverse ecosystems where symbioses play a pivotal role. Corals contain cell-associated microbial aggregates (CAMA), yet little is known about how widespread they are among coral species or the nature of the symbiotic relationship. Using histology, we found CAMA within 24 species of corals from 6 genera from Hawaii, American Samoa, Palmyra, Johnston Atoll, Guam, and Australia. Prevalence (%) of infection varied among coral genera: Acropora, Porites, and Pocillopora were commonly infected whereas Montipora were not. Acropora from the Western Pacific were significantly more likely to be infected with CAMA than those from the Central Pacific, whereas the reverse was true for Porites. Compared with apparently healthy colonies, tissues from diseased colonies were significantly more likely to have both surface and basal body walls infected. The close association of CAMA with host cells in numerous species of apparently healthy corals and lack of associated cell pathology reveals an intimate agent-host association. Furthermore, CAMA are Gram negative and in some corals may be related to chlamydia or rickettsia. We propose that CAMA in adult corals are facultative secondary symbionts that could play an important ecological role in some dominant coral genera in the Indo-Pacific. CAMA are important in the life histories of other animals, and more work is needed to understand their role in the distribution, evolution, physiology, and immunology of reef corals.

Marine Ecology Progress Series↗