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At least 1,189 records · Page 66Linked to original sources
USGS2014

Development of a regionally consistent geospatial dataset of agricultural lands in the Upper Colorado River Basin, 2007-10

Irrigation in arid environments can alter the natural rate at which salts are dissolved and transported to streams. Irrigated agricultural lands are the major anthropogenic source of dissolved solids in the Upper Colorado River Basin (UCRB). Understanding the location, spatial distribution, and irrigation status of agricultural lands and the method used to deliver water to agricultural lands are important to help improve the understanding of agriculturally derived dissolved-solids loading to surface water in the UCRB. Irrigation status is the presence or absence of irrigation on an agricultural field during the selected growing season or seasons. Irrigation method is the system used to irrigate a field. Irrigation method can broadly be grouped into sprinkler or flood methods, although other techniques such as drip irrigation are used in the UCRB. Flood irrigation generally causes greater dissolved-solids loading to streams than sprinkler irrigation. Agricultural lands in the UCRB mapped by state agencies at varying spatial and temporal resolutions were assembled and edited to represent conditions in the UCRB between 2007 and 2010. Edits were based on examination of 1-meter resolution aerial imagery collected between 2009 and 2011. Remote sensing classification techniques were used to classify irrigation status for the June to September growing seasons between 2007 and 2010. The final dataset contains polygons representing approximately 1,759,900 acres of agricultural lands in the UCRB. Approximately 66 percent of the mapped agricultural lands were likely irrigated during the study period.

Arizona, Colorado, New Mexico, Utah, Wyoming↗
USGS1994

Workshop proceedings: research and management in whitebark pine ecosystems

The purpose of this workshop is to exchange information on on-going and soon-to-be-initiated whitebark pine research and management projects. By doing so we hope to encourage future work on this valuable species. We also hope to promote the use of consistent methods for evaluation and investigation of whitebark pine, and to provide avenues of collaboration. Speakers will present information on a variety of topics related to whitebark pine management and research. Featured presentation topics include anthropomorphic utilization of whitepark pine forests, whitebark pine natural regeneration, blister rust and the decline of whitebark pine, blister rust resistance studies, ecological mapping of the species, restoration and management projects, and survey/monitoring techniques. Information gained from these presentations may hopefully be used in the planning of future projects for the conservation of whitebark pine.

Book↗
USGS2017

A land cover change detection and classification protocol for updating Alaska NLCD 2001 to 2011

Monitoring and mapping land cover changes are important ways to support evaluation of the status and transition of ecosystems. The Alaska National Land Cover Database (NLCD) 2001 was the first 30-m resolution baseline land cover product of the entire state derived from circa 2001 Landsat imagery and geospatial ancillary data. We developed a comprehensive approach named AKUP11 to update Alaska NLCD from 2001 to 2011 and provide a 10-year cyclical update of the state's land cover and land cover changes. Our method is designed to characterize the main land cover changes associated with different drivers, including the conversion of forests to shrub and grassland primarily as a result of wildland fire and forest harvest, the vegetation successional processes after disturbance, and changes of surface water extent and glacier ice/snow associated with weather and climate changes. For natural vegetated areas, a component named AKUP11-VEG was developed for updating the land cover that involves four major steps: 1) identify the disturbed and successional areas using Landsat images and ancillary datasets; 2) update the land cover status for these areas using a SKILL model (System of Knowledge-based Integrated-trajectory Land cover Labeling); 3) perform decision tree classification; and 4) develop a final land cover and land cover change product through the postprocessing modeling. For water and ice/snow areas, another component named AKUP11-WIS was developed for initial land cover change detection, removal of the terrain shadow effects, and exclusion of ephemeral snow changes using a 3-year MODIS snow extent dataset from 2010 to 2012. The overall approach was tested in three pilot study areas in Alaska, with each area consisting of four Landsat image footprints. The results from the pilot study show that the overall accuracy in detecting change and no-change is 90% and the overall accuracy of the updated land cover label for 2011 is 86%. The method provided a robust, consistent, and efficient means for capturing major disturbance events and updating land cover for Alaska. The method has subsequently been applied to generate the land cover and land cover change products for the entire state of Alaska.

Alaska↗
USGS2012

Resistivity imaging in eastern Nevada Using the audiomagnetotelluric method for hydrogeologic framework studies

Inversion of audiomagnetotelluric (AMT) sounding data collected in eastern Nevada shows significant structure within the upper kilometer of the subsurface that defines the geologic framework from which hydrologic models will be developed. We collected AMT data along two profiles in Spring and Cave valleys in 2004–2005, using the Geometrics StrataGem EH4 system, a four‐channel, natural and controlled‐source tensor system recording in the range of 10–92,000 Hz. Profiles were 12 and 3 km in length with station spacing of 200–400 m. Two‐dimensional inverse models show detailed structure within the alluvial basin including clear transitions between unsaturated and saturated alluvium/volcanic rocks, highly‐resistive (>1000 ohm‐m) carbonate rocks, and the locations of range‐front and intra‐basin faults. In addition, our results define the shape of and the depth to the basement surface, which correlates well with depth to basement estimates derived from the inversion of gravity data.

Conference Paper↗
USGSDate not supplied

Detecting sulfamethoxazole and carbamazepine in groundwater: Is ELISA a reliable screening tool?

In recent years, numerous studies have reported the prevalence of organic micropollutants in natural waters. There is an increasing interest in assessing the occurrence and transport of these contaminants in groundwater because a large number of people in the United States rely on groundwater for their drinking water. However, commonly used mass-spectrometry-based analytical methods are expensive and time-consuming. The enzyme-linked immunosorbent assay (ELISA) method offers an inexpensive analytical alternative that provides semi-quantitative results in a relatively quick timeframe. We investigated the use of ELISA for two commonly detected micropollutants, sulfamethoxazole (SMX) and carbamazepine (CBZ), in groundwater collected as part of two different studies, one in Minnesota and the other in Iowa. The ELISA results were compared with two mass-spectrometry-based methods: (1) direct aqueous injection-high performance liquid chromatography/tandem mass spectrometry (HPLC) and (2) online solid-phase extraction with liquid chromatography/electrospray ionization-mass spectrometry (SPE LC). Differences in SMX and CBZ observations between ELISA and both HPLC and SPE LC were analyzed using the Paired Prentice-Wilcoxon test. Estimates of bias and limits of agreement between paired observations also were calculated. The SMX determinations by ELISA yielded results that were 30 and 14% greater than HPLC and SPE LC, respectively. The CBZ determinations by ELISA yielded results that were 25 and 9% greater than HPLC and SPE LC, respectively. The ELISA determinations were in presence-absence agreement with HPLC for 83% of samples for SMX and CBZ; and with SPE LC for 76 and 80% of samples for SMX and CBZ, respectively. Results indicate that ELISA for SMX and CBZ is a reliable and cost effective screening-tool alternative to more commonly used mass spectrometry-based analytical methods.

Environmental Pollution↗
USGS2020

Probabilistic regional-scale liquefaction triggering modeling using 3D Gaussian processes

Liquefaction is a major cause of coseismic damages, occurring irregularly over hundreds or thousands of square kilometers in large earthquakes. Large variations in the extent and location of liquefaction have been observed in recent earthquakes, motivating the need for prediction methods that consider the spatial heterogeneity of geologic deposits at a regional scale. Contemporary regional-scale liquefaction hazard analyses are typically performed using only surficial data, which does not address the complicated subsurface mechanics and spatial variability associated with artificial fill and natural soil deposits. In this study, we develop a probabilistic, regional-scale, subsurface model using data from hundreds of borings to better understand subsurface conditions that could influence liquefaction. We then use this subsurface sample database to train Gaussian process models, yielding 3D independent random fields of groundwater depth, soil plasticity, and penetration resistance for each geologic unit. We incorporate the Gaussian process models into probabilistic liquefaction triggering procedures, producing 3D estimates of the probability of liquefaction for an example study area in Portland, Oregon. Near sampling locations, the variance of the Gaussian process models approaches the variance of site-specific liquefaction triggering procedures. Conversely, when no sample data are nearby to condition a Gaussian process, the variance approaches the marginal variance of the entire recorded dataset. Thus, the procedure described in this study unifies probabilistic site-specific and regional-scale liquefaction triggering procedures and provides an important step towards quantitative liquefaction hazard assessments for regionally distributed infrastructures, such as levees, pipelines, roadways, and electrical transmission facilities.

Oregon↗
USGS2001

Recent formation of arroyos in the Little Missouri Badlands of southwestern North Dakota

In the Little Missouri Badlands of southwestern North Dakota, the channels of ephemeral streams are incised 2 to 10 m or more into mid-to-late Holocene alluvium. The objectives of this study were to determine the timing and cause(s) of the most recent episodes of fluvial incision and to develop a process-response model that illustrates the formation and evolution of arroyos in this region. The purpose was to distinguish natural from anthropogenic changes to the landscape and to discriminate allogenic from autogenic causes of incision, thereby gaining a greater sense of how steep, relatively small, ephemeral streams evolve. Dendrochronologic and dendrogeomorphic analyses of riparian cottonwoods provide an inexpensive, high-resolution dating method to constrain the time of incision, thereby permitting determination of the cause(s) of incision by evaluating environmental conditions prior to and at the onset of fluvial incision. An examination of seven small (10 to 100 km2) drainage basins indicated ephemeral streams have undergone a four-stage cycle of change within the past 200 years, comprising(i) an initial period of relative geomorphic stability with pedogenesis on the flood plain and low rates of lateral channel migration, (ii) a period of channel incision with subsequent widening of the flood plain through lateral corrasion along middle and upstream reaches, (iii) a concomitant period of aggradation along downstream reaches and, finally, (iv) a period of downstream incision. Dendrochronologic data and dendrogeomorphic relations indicate there have been three distinct periods of fluvial incision in the past 200 years. The first period of incision began in the 1860s and 1870s prior to the onset of European settlement and intensive grazing by domesticated cattle in the area. This period of incision occurred along the middle reaches of all seven of the streams examined and coincided with a severe, protracted drought, suggesting an allogenic cause. The second period of incision occurred during the end of the 19th century and into the 20th century along the upstream reaches of streams. This period of incision was mentioned in some written accounts of early settlers and coincided with the introduction of cattle and historical overgrazing of the region. However, overgrazing may not have caused the incision of this period, but instread exacerbated or accelerated the upstream migration of knickpoints formed earlier along middle reaches. A third period of incision has occurred in the past 20 years along the lower reaches of two of the seven streams examined. This incision was caused by the process of meander cutoff. This autogenic process decreases sinuosity and increases channel slope, stream power, and the potential to incise along adjacent stream reaches. ?? 2001 Elsevier Science B.V. All rights reserved.

Geomorphology↗
USGS2006

North Slope, Alaska: Source rock distribution, richness, thermal maturity, and petroleum charge

Four key marine petroleum source rock units were identified, characterized, and mapped in the subsurface to better understand the origin and distribution of petroleum on the North Slope of Alaska. These marine source rocks, from oldest to youngest, include four intervals: (1) Middle-Upper Triassic Shublik Formation, (2) basal condensed section in the Jurassic-Lower Cretaceous Kingak Shale, (3) Cretaceous pebble shale unit, and (4) Cretaceous Hue Shale. Well logs for more than 60 wells and total organic carbon (TOC) and Rock-Eval pyrolysis analyses for 1183 samples in 125 well penetrations of the source rocks were used to map the present-day thickness of each source rock and the quantity (TOC), quality (hydrogen index), and thermal maturity (Tmax) of the organic matter. Based on assumptions related to carbon mass balance and regional distributions of TOC, the present-day source rock quantity and quality maps were used to determine the extent of fractional conversion of the kerogen to petroleum and to map the original TOC (TOCo) and the original hydrogen index (HIo) prior to thermal maturation. The quantity and quality of oil-prone organic matter in Shublik Formation source rock generally exceeded that of the other units prior to thermal maturation (commonly TOCo > 4 wt.% and HIo > 600 mg hydrocarbon/g TOC), although all are likely sources for at least some petroleum on the North Slope. We used Rock-Eval and hydrous pyrolysis methods to calculate expulsion factors and petroleum charge for each of the four source rocks in the study area. Without attempting to identify the correct methods, we conclude that calculations based on Rock-Eval pyrolysis overestimate expulsion factors and petroleum charge because low pressure and rapid removal of thermally cracked products by the carrier gas retards cross-linking and pyrobitumen formation that is otherwise favored by natural burial maturation. Expulsion factors and petroleum charge based on hydrous pyrolysis may also be high compared to nature for a similar reason. Copyright ?? 2006. The American Association of Petroleum Geologists. All rights reserved.

American Association of Petroleum Geologists Bulle↗
USGS2009

Approaches to modelling uranium (VI) adsorption on natural mineral assemblages

Component additivity (CA) and generalised composite (GC) approaches to deriving a suitable surface complexation model for description of U(VI) adsorption to natural mineral assemblages are pursued in this paper with good success. A single, ferrihydrite-like component is found to reasonably describe uranyl uptake to a number of kaolinitic iron-rich natural substrates at pH > 4 in the CA approach with previously published information on nature of surface complexes, acid-base properties of surface sites and electrostatic effects used in the model. The GC approach, in which little pre-knowledge about generic surface sites is assumed, gives even better fits and would appear to be a method of particular strength for application in areas such as performance assessment provided the model is developed in a careful, stepwise manner with simplicity and goodness of fit as the major criteria for acceptance.

Radiochimica Acta↗
USGS2006

Audiomagnetotelluric data from Spring, Cave, and Coyote Spring Valleys, Nevada

Audiomagnetotelluric (AMT) data along four profiles in Spring, Cave, and Coyote Spring Valleys are presented here. The AMT method is used to estimate the electrical resistivity of the earth over depth ranges of a few meters to greater than one kilometer. This method is a valuable tool for revealing subsurface structure and stratigraphy within the Basin and Range of eastern Nevada, therefore helping to define the geohydrologic framework in this region. We collected AMT data using the Geometrics StrataGem EH4 system, a four-channel, natural and controlled- source tensor system recording in the range of 10 to 92,000 Hz. To augment the low signal in the natural field, an unpolarized transmitter comprised of two horizontal-magnetic dipoles was used from 1,000 to 70,000 Hz. Profiles were 1.4 - 12.6 km in length with station spacing of 100-400 m. Data were recorded with the electrical (E) field parallel to and perpendicular to the regional geologic strike direction. Station locations and sounding curves, showing apparent resistivity, phase data, and coherency data, are presented here.

Open-File Report↗
USGS2006

Bathymetric map of the north part of Great Salt Lake, Utah, 2006

The U.S. Geological Survey, in cooperation with the Utah Department of Natural Resources, Division of Forestry, Fire, and State Lands, collected bathymetric data for the north part of Great Salt Lake during the spring and early summer of 2006 using a single beam, high-definition fathometer and real-time differential global positioning system. Approximately 5.2 million depth readings were collected along more than 765 miles of survey transects for construction of this map. Sound velocities were obtained in conjunction with the bathymetric data to provide time-of-travel corrections to the depth calculations. Data were processed using commercial hydrographic software and exported into a geographic information system (GIS) software for mapping. Due to the shallow nature of the lake and the limitations of the instrumentation, contours above an altitude of 4,194 feet were digitized from existing USGS 1:24,000 source-scale digital line graph data. The Behrens Trench is approximately located. For additional information on methods used to derive the bathymetric contours for this map, please see Baskin, Robert L., 2006, Calculation of area and volume for the North Part of Great Salt Lake, Utah, U.S. Geological Survey Open-File Report OFR–2006–1359

Utah↗
USGS1978

Preliminary appraisal of the geohydrologic aspects of drainage wells, Orlando area, central Florida

The Floridan aquifer contains two highly transmissive cavernous zones in the Orlando area: an upper producing zone about 150-600 feet below land surface; and a lower producing zone about 1,100-1,500 feet below land surface. Natural head differences are downward and there is hydraulic connection between the two producing zones. Drainage wells are finished open-end into the upper producing zone and emplace surface waters directly into that zone by gravity. Quantitatively, their use constitutes an effective method of artificial recharge. Their negative aspects relate to the probably poor, but unknown, quality of the recharge water. Caution is suggested in drawing definite and final conclusions on the overall geohydrologic and environmental effects of drainage wells prior to the collection and interpretation of a considerable quantity of new data. Though few ground-water pollution problems have been documented to date, the potential for such pollution should be seriously considered in light of the prob-able continuing need to use drainage wells; the probable volumes and quality of water involved; and the hydraulic relations between the two producing zones.

Florida↗
USGS2002

Reducing predation by common ravens on desert tortoises in the Mojave and Colorado Deserts

Conflicts between humans and natural populations often result from habitat fragmentation and degradation that accompanies human activities. Common raven populations in the Mojave Desert have benefited by human-provided resources; they've expanded precipitously in recent years. Because ravens prey on juveniles of the threatened desert tortoise, they have become the focus of management concerns to help recover dwindling tortoise populations. I have outlined herein a series of management recommendations designed to reduce raven predation on desert tortoises thereby facilitating juvenile tortoise recruitment into the population of reproductive adults. The recommendations are based on the best available scientific information and are intended to provide a basis for a long-term reduction in raven impacts. The recommendations fall into four basic categories. (1) Modify anthropogenic sources of food, water, and nesting substrates to reduce their use by ravens. This includes modifying landfill operations, septage containment practices, livestock management, and other commercial and private practices that help facilitate raven survival and dispersal by providing food and water. Most of these measures are long-term actions deigned to reduce the carrying capacity of the desert for ravens. This action is critical and must be done over very large areas. (2)Lethal removal of ravens by shooting or euthanizing following live trapping. Specific ravens known to prey on tortoises would be targeted as well as all ravens found foraging within specific high-priority desert tortoise management zones (e.g., Desert Tortoise Natural Areas, DTNA). These actions would primarily be deployed on a short-term emergency basis to give specific tortoise populations a necessary boost until other measures become fully implemented and achieve their goals. (3) Conduct research on raven ecology, raven behavior, and methods to reduce raven predation on tortoises. Results of these studies would be used to design future phases of the raven management program. (4) All actions should be approached within an adaptive management framework. As such monitor, actions should be designed as experiments so that monitoring of actions will yield reliable and scientifically sound results. Coordinating and oversight teams should be convened to facilitate cooperation and coordination among agencies and to ensure that the actions are being implemented effectively. Recommendations made herein were developed to help recover tortoise populations by reducing raven predation on juvenile tortoises. If the recommendations made are implemented in concert with actions reducing other causes of mortality, ill health, and lowered reproductive output, they should aid in the long-term recovery of desert tortoise populations. Many important aspects of raven population dynamics, raven predation on tortoises, and how to manage raven populations and behavior are as yet unknown. Because of this, any raven management program must be implemented within an adaptive management framework. Doing so would allow for sufficient flexibility to modify the program as new information is gained.

Report↗
USGS2004

Natural selection of the major histocompatibility complex (Mhc) in Hawaiian honeycreepers (Drepanidinae)

The native Hawaiian honeycreepers represent a classic example of adaptive radiation and speciation, but currently face one the highest extinction rates in the world. Although multiple factors have likely influenced the fate of Hawaiian birds, the relatively recent introduction of avian malaria is thought to be a major factor limiting honeycreeper distribution and abundance. We have initiated genetic analyses of class II ?? chain Mhc genes in four species of honeycreepers using methods that eliminate the possibility of sequencing mosaic variants formed by cloning heteroduplexed polymerase chain reaction products. Phylogenetic analyses group the honeycreeper Mhc sequences into two distinct clusters. Variation within one cluster is high, with dN > d S and levels of diversity similar to other studies of Mhc (B system) genes in birds. The second cluster is nearly invariant and includes sequences from honeycreepers (Fringillidae), a sparrow (Emberizidae) and a blackbird (Emberizidae). This highly conserved cluster appears reminiscent of the independently segregating Rfp-Y system of genes defined in chickens. The notion that balancing selection operates at the Mhc in the honeycreepers is supported by transpecies polymorphism and strikingly high dN/dS ratios at codons putatively involved in peptide interaction. Mitochondrial DNA control region sequences were invariant in the i'iwi, but were highly variable in the 'amakihi. By contrast, levels of variability of class II ?? chain Mhc sequence codons that are hypothesized to be directly involved in peptide interactions appear comparable between i'iwi and 'amakihi. In the i'iwi, natural selection may have maintained variation within the Mhc, even in the face of what appears to a genetic bottleneck.

Molecular Ecology↗
USGS2026

Best practice guidelines for targeted environmental DNA-based proficiency testing in non-regulatory contexts

The effective use of environmental DNA (eDNA) tools is contingent on strict adherence to established and validated methods. Differences in eDNA methods and quality assurance protocols may contribute to variability in results. However, quality assurance measures such as proficiency testing can provide independent evaluation of laboratory performance against pre-established test criteria. With this commentary, we discuss how broad implementation of recurring proficiency testing in eDNA laboratories can build decision-maker confidence in eDNA results. It can also create a culture of continuous evaluation and improvement that minimizes error and meets performance requirements to inform the sustainable use or monitoring of natural resources. We provide an overview of proficiency testing across molecular disciplines, review the state of proficiency testing in eDNA applications, and draft a roadmap for the expanded application of proficiency testing informed by best practices for targeted eDNA detection. We suggest that best practice proficiency testing can be conducted by an independent, third-party sample provider. By demonstrating that laboratories are competent and capable of producing reliable results, implementation of proficiency testing best practices should foster confidence in eDNA measurements and its use in decision-making processes. Increased confidence in eDNA methods and a clear expectation of what is considered satisfactory performance are also likely to create more favorable conditions for investments in eDNA-based monitoring.

Environmental DNA↗
USGS2025

Hydrologic connectivity in floodplain systems: A multiscale review of concepts, metrics and management

Hydrologic connectivity (HC), particularly in floodplain systems, is pivotal in regulating ecosystem services by facilitating the movement of nutrients, sediments, chemicals, and biota. However, human interventions such as dam construction, levee installation, water management practices, and alterations in vegetation have significantly disrupted natural HC patterns globally. To provide a structured entry into the growing body of HC research, we conducted a systematic literature review of 1920 studies, analysing diverse definitions, influencing factors, quantification approaches, spatial and temporal scales, and management strategies. In addition to traditional review methods, our approach integrates keyword and cluster analysis to elucidate dominant research themes and trends across the literature. Our review reveals that the literature is heavily skewed towards research in North America and Europe (accounting for 72% of studies) and predominantly utilises field investigations, simulation modelling, and remote sensing integrated with geographic information systems. Although these methodologies have advanced our understanding, most studies focus on restricted spatial scales such as individual hillslopes, catchments, or stream networks and short temporal intervals, including single precipitation events or seasonal cycles. A narrow focus becomes a limitation when such studies do not contribute to broader efforts aimed at scaling insights across larger domains. These limitations highlight the potential benefits of innovative conceptual frameworks and quantification methods to better capture HC across broader environments and extended temporal scales. We conclude by discussing challenges in defining and quantifying floodplain HC and outlining potential future research directions to advance connectivity science and management, particularly in floodplain systems characterised by frequent hydrologic fluctuations, such as seasonal inundation and changing flow paths.

Hydrological Processes↗
USGS2009

Continental-scale patterns in soil geochemistry and mineralogy: results from two transects across the United States and Canada

In 2004, the US Geological Survey (USGS) and the Geological Survey of Canada (GSC) initiated a pilot study that involved collection of more than 1500 soil samples from 221 sites along two continental transects across Canada and the United States. The pilot study was designed to test and refine protocols for a soil geochemical survey of North America. The two transects crossed a wide array of soil parent materials, soil ages, climatic conditions, landforms, land covers and land uses. Sample sites were selected randomly at approximately 40-km intervals from a population defined as all soils of the continent. At each site, soils representing 0 to 5 cm depth, and the O, A, and C horizons, if present, were collected and analyzed for their near-total content of over 40 major and trace elements. Soils from 0–5 cm depth were also collected for analysis of organic compounds. Results from the transects confirm that soil samples collected at a 40-km spacing reveal coherent, continental- to subcontinental-scale geochemical and mineralogical patterns that can be correlated to aspects of underlying soil parent material, soil age and climate influence. The geochemical data also demonstrate that at the continental-scale the dominance of any of these major factors that control soil geochemistry can change across the landscape. Along both transects, soil mineralogy and geochemistry change abruptly with changes in soil parent materials. However, the chemical influence of a soil’s parent material can be obscured by changing climatic conditions. For the transects, increasing precipitation from west to east and increasing temperature from north to south affect both soil mineralogy and geochemistry because of climate effects on soil weathering and leaching, and plant productivity. Regional anomalous metal concentrations can be linked to natural variations in soil parent materials, such as high Ni and Cr in soils developed on ultramafic rocks in California or high P in soils formed on weathered Ordovician limestones in central Kentucky. On local scales, anomalous metal concentrations recognized in soil profiles, such as high P in soils from animal confinement sites, are consistent with local anthropogenic disturbances. At a larger scale, the distribution of Hg across the west to east transect demonstrates that it can be difficult to distinguish between natural or anthropogenic contributions and that many factors can contribute to an element’s spatial distribution. Only three samples in a subset of seventy-three 0–5 cm depth soil samples from the north to south transect had organochlorine pesticides values above the method detection limit, apparently related to historic usage of the pesticides DDT and dieldrin.

Applied Geochemistry↗
USGS2021

Biological and practical tradeoffs in planting techniques for submerged aquatic vegetation

Global loss of submerged aquatic vegetation (SAV) and associated ecosystem function has prompted an interest in SAV revegetation, particularly where underlying stressors such as nutrient enrichment are mitigated, yet natural recruitment remains low. Typically, SAV is hand-planted, but alternative reliable and practically scalable SAV planting techniques are needed. In mesocosms, we evaluated five planting techniques: 1) hand planting, anchoring using 2) fishing weights and 3) plaster blocks, and sediment-added methods using 4) peat pots and 5) burlap-wraps (“burritos”). Anchoring and sediment-added techniques were also field evaluated at four locations within a single lake. In mesocosms, all techniques effectively established two common North American SAV species, Vallisneria americana and Potamogeton illinoensis . Sediment-added techniques had species-specific benefits, e.g. burritos produced taller Vallisneria leaves, and greater Potamogeton biomass, while peat pots encouraged rapid Vallisneria shoot production. However, no treatment was universally beneficial across all growth metrics. In the field, all techniques were effective at two sites, but at two other sites, no techniques were successful. Results show that under favorable mesocosm and field conditions, all techniques promote establishment; however, subtle differences in technique-driven plant traits (height, density, nutrients) suggest that under specific environmental conditions, some techniques may be more favorable. Also, no technique offers practical advantages in every scenario, but each offers situation-specific advantages. Guidance emerging from this work is that all techniques are potentially effective, but small-scale tests in site-specific restoration scenarios, along with consideration of feasibility constraints, are recommended to inform large-scale plantings.

Aquatic Botany↗