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USGS2011

Recent and historic drivers of landscape change in the Everglades ridge, slough, and Tree Island mosaic

More than half of the original Everglades extent formed a patterned peat mosaic of elevated ridges, lower and more open sloughs, and tree islands aligned parallel to the dominant flow direction. This ecologically important landscape structure remained in a dynamic equilibrium for millennia prior to rapid degradation over the past century in response to human manipulation of the hydrologic system. Restoration of the patterned landscape structure is one of the primary objectives of the Everglades restoration effort. Recent research has revealed that three main drivers regulated feedbacks that initiated and maintained landscape structure: the spatial and temporal distribution of surface water depths, surface and subsurface flow, and phosphorus supply. Causes of recent degradation include but are not limited to perturbations to these historically important controls; shifts in mineral and sulfate supply may have also contributed to degradation. Restoring predrainage hydrologic conditions will likely preserve remaining landscape pattern structure, provided a sufficient supply of surface water with low nutrient and low total dissolved solids content exists to maintain a rainfall-driven water chemistry. However, because of hysteresis in landscape evolution trajectories, restoration of areas with a fully degraded landscape could require additional human intervention.

Critical Reviews in Environmental Science and Tech↗

USGS2017

Field study suggests that sex determination in sea lamprey is directly influenced by larval growth rate

Sex determination mechanisms in fishes lie along a genetic-environmental continuum and thereby offer opportunities to understand how physiology and environment interact to determine sex. Mechanisms and ecological consequences of sex determination in fishes are primarily garnered from teleosts, with little investigation into basal fishes. We tagged and released larval sea lamprey ( Petromyzon marinus ) into unproductive lake and productive stream environments. Sex ratios produced from these environments were quantified by recapturing tagged individuals as adults. Sex ratios from unproductive and productive environments were initially similar. However, sex ratios soon diverged, with unproductive environments becoming increasingly male-skewed and productive environments becoming less male-skewed with time. We hypothesize that slower growth in unproductive environments contributed to the sex ratio differences by directly influencing sex determination. To the best of our knowledge, this is the first study suggesting that growth rate in a fish species directly influences sex determination; other studies have suggested that the environmental variables to which sex determination is sensitive (e.g. density, temperature) act as cues for favourable or unfavourable growth conditions. Understanding mechanisms of sex determination in lampreys may provide unique insight into the underlying principles of sex determination in other vertebrates and provide innovative approaches for their management where valued and invasive.

Proceedings of the Royal Society B: Biological Sci↗

USGS2011

Relationships between silicic plutonism and volcanism: Geochemical evidence

Field associations (voluminous ash flow deposits, rhyolitic stocks and dykes, ring complexes), evidence of repeated influxes of mafic magma, and thermal constraints indicate that many high-level silicic plutons (magma chambers) acted as open systems for considerable parts of their history. The long thermal lifetime, as well as other evidence from the volcanic record, suggests that some such systems reached a quasi-steady state in which magma input was balanced by magma output for times longer than those required for crystallisation. Reconstruction of the evolution of large, long-lived caldera-forming systems, such as that of the Jemez Mountains, New Mexico, indicates that many chambers have lost a highly fractionated silicic cap, in some cases cyclically. Crystallised plutons may contain no obvious record of this evolutionary phase. Geochemical data from silicic ash flow deposits can be used to reconstruct the volcanic stage of pluton development. Many silicic systems, especially of alkaline affinity, apparently pass from a stage in which melt evolution is dominated by crystal-liquid processes to one in which other processes may also contribute to differentiation. Apparently, the transition is most readily achieved in volatile-rich, alkaline silicic systems emplaced in complex, ancient sialic crust of the cratons. Once established, the preservation of highly fractionated caps on magma chambers requires a balance between thermal input and cooling-induced crystallisation. If heat enters the system too quickly, the cap may get stirred into the dominant magma volume by convection. If heat input is too slow, the magma body will crystallise inward from the margins, and the plutonic-consolidation stage will begin. © 1988, Royal Society of Edinburgh. All rights reserved.

Transactions of the Royal Society of Edinburgh, Ea↗

USGS2021

Persistent nitrate in alpine waters with changing atmospheric deposition and warming trends

Nitrate concentrations in high-elevation lakes of the Colorado Front Range remain elevated despite declining trends in atmospherically deposited nitrate since 2000. The current source of this elevated nitrate in surface waters remains elusive, given shifts in additional nitrogen sources via glacial inputs and atmospheric ammonium deposition. We present the complete isotopic composition of nitrate (δ 15 N, δ 18 O, and Δ 17 O) from a suite of nitrate-bearing source waters collected during the summers of 2017–2018 from two alpine ecosystems to constrain the provenance of elevated nitrate in surface waters during the summer open-water season. The results indicate a consistent contribution of uncycled atmospheric nitrate throughout the summer (13–23%) to alpine lakes, despite seasonal changes in source water inputs. The balance of nitrate (as high as 87% in late summer) is likely from nitrate production within the catchment via nitrification of reduced nitrogen sources (e.g., thawed soil organic matter and ammonium deposition) and released with rock glacier meltwater. The role of microbially produced nitrate has become increasingly important over time based on historical surface water samples from the mid-90s to present, a trend coincident with increasing ammonium deposition to alpine systems.

Colorado↗

USGS2011

Project plan-Surficial geologic mapping and hydrogeologic framework studies in the Greater Platte River Basins (Central Great Plains) in support of ecosystem and climate change research

The Greater Platte River Basin area spans a central part of the Midcontinent and Great Plains from the Rocky Mountains on the west to the Missouri River on the east, and is defined to include drainage areas of the Platte, Niobrara, and Republican Rivers, the Rainwater Basin, and other adjoining areas overlying the northern High Plains aquifer. The Greater Platte River Basin contains abundant surficial deposits that were sensitive to, or are reflective of, the climate under which they formed: deposits from multiple glaciations in the mountain headwaters of the North and South Platte Rivers and from continental ice sheets in eastern Nebraska; fluvial terraces (ranging from Tertiary to Holocene in age) along the rivers and streams; vast areas of eolian sand in the Nebraska Sand Hills and other dune fields (recording multiple episodes of dune activity); thick sequences of windblown silt (loess); and sediment deposited in numerous lakes and wetlands. In addition, the Greater Platte River Basin overlies and contributes surface water to the High Plains aquifer, a nationally important groundwater system that underlies parts of eight states and sustains one of the major agricultural areas of the United States. The area also provides critical nesting habitat for birds such as plovers and terns, and roosting habitat for cranes and other migratory birds that travel through the Central Flyway of North America. This broad area, containing fragile ecosystems that could be further threatened by changes in climate and land use, has been identified by the USGS and the University of Nebraska-Lincoln as a region where intensive collaborative research could lead to a better understanding of climate change and what might be done to adapt to or mitigate its adverse effects to ecosystems and to humans. The need for robust data on the geologic framework of ecosystems in the Greater Platte River Basin has been acknowledged in proceedings from the 2008 Climate Change Workshop and in draft reports by researchers developing a multidisciplinary science plan for the Greater Platte River Basin.

Open-File Report↗

USGS2002

Arctic Refuge coastal plain terrestrial wildlife research summaries

In 1980, when the U.S. Congress enacted the Alaska National Interest Lands Conservation Act (ANILCA), it also mandated a study of the coastal plain of the Arctic National Wildlife Refuge. Section 1002 of ANILCA stated that a comprehensive inventory of fish and wildlife resources would be conducted on 1.5 million acres of the Arctic Refuge coastal plain (1002 Area). Potential petroleum reserves in the 1002 Area were also to be evaluated from surface geological studies and seismic exploration surveys. Results of these studies and recommendations for future management of the Arctic Refuge coastal plain were to be prepared in a report to Congress. In 1987, the Department of the Interior published the Arctic National Wildlife Refuge, Alaska, Coastal Plain Resource Assessment - Report and Recommendations to the Congress of the United States and Final Environmental Impact Statement. This report to Congress identified the potential for oil and gas production (updated* most recently by the U.S. Geological Survey in 2001), described the biological resources, and evaluated the potential adverse effects to fish and wildlife resources. The 1987 report analyzed the potential environmental consequences of five management alternatives for the coastal plain, ranging from wilderness designation to opening the entire area to lease for oil and gas developement. The report's summary recommended opening the 1002 Area to an orderly oil and gas leasing program, but cautioned that adverse effects to some wildlife populations were possible. Congress did not act on this recommendation nor any other alternative for the 1002 Area, and scientists continued studies of key wildlife species and habitats on the coastal plain of the Arctic Refuge and surrounding areas. This report contains updated summaries of those scientific investigations of caribou, muskoxen, predators (grizzly bears, wolves, golden eagles), polar bears, snow geese, and their wildlife habitats. Contributions to this report were made by scientists affiliated with the U.S. Geological Survey; U.S. Fish and Wildlife Service; Alaska Department of Fish and Game; University of Alaska-Fairbanks; Canadian Wildlife Service; Yukon Department of Renewable Resources; and the Northwest Territories Department of Resources, Wildlife, and Economic Development. Sections of the report presenting new information on caribou and forage plants were peer-reviewed by three independent, non-affiliated scientists. The remaining sections summarize previously published peer-reviewed scientific papers and were reviewed by a single independent scientist. The U.S. Geological Survey and the U.S. Fish and Wildlife Service collaborated in the publication of this report.

Alaska, Northwest Territories, Yukon Territory↗

USGS2020

Book review: Proceedings of the First International Snakehead Symposium

Snakehead fishes (family Channidae) are among the most maligned aquatic invasive species in the USA and some other countries where they have been introduced outside of their native range in Asia and Africa. Nevertheless, snakeheads continue to be widely exploited in the live‐food trade in aquaculture and wild‐capture fisheries, are highly sought by anglers, and are also popular in the aquarium trade (Courtenay and Williams 2004). The Northern Snakehead Channa argus is the most widespread of the three channid species that are currently naturalized in the USA. This species has generated much concern and controversy, a situation that is partly fueled by sensational media coverage and B‐grade science fiction horror films, such as “Frankenfish,” “Snakehead Terror,” and “Snakehead Swamp.” Media reports of snakehead introductions are often replete with provocative terms, such as “vicious,” “villain,” “voracious,” “monster,” “diabolical,” and even “ecological Armageddon.” When snakeheads first appeared in natural waters of the USA, fisheries professionals became increasingly interested in their status. Established populations rapidly expanded in the mid‐Atlantic region and Arkansas, with scattered reports of introduced snakeheads from isolated locations in Hawaii, California, North Carolina, Florida, the Upper Midwest, and New England. In 2002, snakeheads were added to the list of injurious fishes under the Lacey Act, thereby prohibiting their importation or transport across state lines without a permit. This symposium was conceived by the editors and other concerned fisheries professionals of the Mississippi River Basin Panel on Aquatic Invasive Species. The mission of the symposium, held in Alexandria, Virginia, in July 2018, was to bring together experts on snakehead biology and ecology and to synthesize existing information into summary papers. In this book, 35 authors contributed to 15 peer‐reviewed articles that detail the current state of knowledge about snakehead introductions in the USA. Additionally, 16 abstracts are included from meeting presentations that were not accompanied by full‐length manuscripts. Also included is a summary of a facilitated symposium panel discussion featuring eight experts representing state and federal natural resource agencies and private fishing organizations. The book is organized into six sections. In the first section (Distribution), three papers provide an overview of the Channa species introduced into the USA and historical accounts of occurrence and dispersal of the Northern Snakehead in the mid‐Atlantic region and Arkansas. The second section (Biology/Ecology) consists of two articles that examine growth and energetics of Northern Snakehead populations and two papers that investigate diet, diel feeding activity, and movement of this species in the Potomac River drainage. The third section (Monitoring/Response) includes a paper that models range expansion of the Northern Snakehead in the southeastern USA based on occurrence data and environmental conditions. Also included in this section is a paper summarizing an environmental DNA study to assess the status and range of the Bullseye Snakehead C. marulius in southern Florida. The fourth section (Management/Control) is comprised of four papers that address harvest, age and growth, and development of a stock–recruitment model to inform management decisions regarding control and mitigation for Northern Snakehead populations in the greater Chesapeake Bay area. The fifth section (Perspectives) includes a paper on the history of snakehead introductions in Japan and a thought‐provoking social commentary on the human dimensions of Northern Snakehead management. Abstracts in the final section provide brief summaries of a diversity of snakehead studies, including aspects of distribution, ecology, behavior, control and monitoring efforts, public outreach, and pathology. The summary of the panel discussion is an engaging dialogue about the challenges of snakehead management in the context of conflicts regarding snakeheads as injurious versus their value as game and food species. Most of this book is focused on the Northern Snakehead. Much has been done to document snakehead distributions and certain aspects of snakehead biology, such as diets, age, and growth. Less research has been devoted to understanding the ecological impacts of snakeheads to native aquatic communities and ecosystems. This book would have benefited from a chapter summarizing the current systematics and diversity of the Channidae to inform fisheries biologists about the morphological characteristics of the family, approximate numbers of genera and species, and taxonomic instability. Exemplifying the latter, recent molecular and morphological evidence indicates uncertainty regarding identification of the feral snakehead population in Florida (Adamson and Britz 2019). Those authors suggest that this population may have originated from western Thailand, a possibility that could have implications for understanding historical pathways of snakehead introductions into the USA. In comparison with many published AFS symposia, this volume is relatively narrow in scope and lacks cohesive integration. It will primarily be of interest to those fisheries professionals engaged in the study of snakeheads as well as other nonnative species for which there are contrasting social values regarding their management: whether to monitor and attempt control or eradication efforts or to maintain populations for harvest as game or food species. The book should serve to identify information gaps and guide future research.

Transactions of the American Fisheries Society↗

USGS2025

Municipal and industrial wastewater treatment plant effluent contributions to per- and polyfluoroalkyl substances in the Potomac River: A basin-scale measuring and modeling approach

Managing per- and polyfluoroalkyl substances (PFAS) in water resources requires a basin-scale approach. Predicted environmental concentrations (PEC) and stream-vulnerability scores for PFAS were determined for the Potomac River watershed in the eastern United States. Approximately 15% of stream reaches contained municipal and/or industrial wastewater treatment plant (WWTP) discharges that are presumptive PFAS sources, comprising from <1 to >90% of streamflow. Mean annual PEC, based on the summed concentrations of eight PFAS detected in WWTP effluents (ΣPFAS PEC ), for all stream reaches in the watershed was 3.8 ng L –1 , and stream reaches impacted by WWTP had perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) PEC of 0.39 and 0.14 ng L –1 . For locations where measured-environmental concentrations (MEC) were determined, municipal and industrial WWTP contributed 7.8% (0 to 65%) of the total annual streamflow and MEC were greater than PEC in 99% of the samples, indicating additional potential PFAS sources. The mean ΣPFAS PEC was 9.1 ng L –1 compared to a mean sum of PFAS MEC of 34 ng L –1 . Under mean-August low-flow, 17% and 9.4% of the water-supply intakes had maximum PFOA and PFOS PEC exceeding drinking water maximum contaminant levels.

Maryland, Pennsylvania, Virginia, West Virginia↗

USGS2011

Fish as major carbonate mud producers and missing components of the tropical carbonate factory

Carbonate mud is a major constituent of recent marine carbonate sediments and of ancient limestones, which contain unique records of changes in ocean chemistry and climate shifts in the geological past. However, the origin of carbonate mud is controversial and often problematic to resolve. Here we show that tropical marine fish produce and excrete various forms of precipitated (nonskeletal) calcium carbonate from their guts (“low” and “high” Mg-calcite and aragonite), but that very fine-grained (mostly < 2 μm) high Mg-calcite crystallites (i.e., MgCO 3 ) are their dominant excretory product. Crystallites from fish are morphologically diverse and species-specific, but all are unique relative to previously known biogenic and abiotic sources of carbonate within open marine systems. Using site specific fish biomass and carbonate excretion rate data we estimate that fish produce ∼6.1 × 10 6 kg CaCO 3 /year across the Bahamian archipelago, all as mud-grade (the < 63 μm fraction) carbonate and thus as a potential sediment constituent. Estimated contributions from fish to total carbonate mud production average ∼14% overall, and exceed 70% in specific habitats. Critically, we also document the widespread presence of these distinctive fish-derived carbonates in the finest sediment fractions from all habitat types in the Bahamas, demonstrating that these carbonates have direct relevance to contemporary carbonate sediment budgets. Fish thus represent a hitherto unrecognized but significant source of fine-grained carbonate sediment, the discovery of which has direct application to the conceptual ideas of how marine carbonate factories function both today and in the past.

Proceedings of the National Academy of Sciences of↗

USGS2015

Porewater dynamics of silver, lead and copper in coastal sediments and implications for benthic metal fluxes

To determine the conditions that lead to a diffusive release of dissolved metals from coastal sediments, porewater profiles of Ag, Cu, and Pb have been collected over seven years at two contrasting coastal sites in Massachusetts, USA. The Hingham Bay (HB) site is a contaminated location in Boston Harbor, while the Massachusetts Bay (MB) site is 11 km offshore and less impacted. At both sites, the biogeochemical cycles include scavenging by Fe-oxyhydroxides and release of dissolved metals when Fe-oxyhydroxides are reduced. Important differences in the metal cycles at the two sites, however, result from different redox conditions. Porewater sulfide and seasonal variation in redox zone depth is observed at HB, but not at MB. In summer, as the conditions become more reducing at HB, trace metals are precipitated as sulfides and are no longer associated with Fe-oxyhydroxides. Sulfide precipitation close to the sediment–water interface limits the trace metal flux in summer and autumn at HB, while in winter, oxidation of the sulfide phases drives high benthic fluxes of Cu and Ag, as oxic conditions return. The annual diffusive flux of Cu at HB is found to be significant and contributes to the higher than expected water column Cu concentrations observed in Boston Harbor. At MB, due to the lower sulfide concentrations, the association of trace metals with Fe-oxyhydroxides occurs throughout the year, leading to more stable fluxes. A surface enrichment of solid phase trace metals was found at MB and is attributed to the persistent scavenging by Fe-oxyhydroxides. This process is important, particularly at sites that are less reducing, because it maintains elevated metal concentrations at the surface despite the effects of bioturbation and sediment accumulation, and because it may increase the persistence of metal contamination in surface sediments.

Massachusetts↗

USGS2018

Cooperative Fish and Wildlife Research Units Program—2017 year in review

The Cooperative Fish and Wildlife Research Units Program was involved in a number of notable events during 2017, many concerning our personnel. Dr. Barry Grand left his position as Leader of the Alabama Cooperative Fish and Wildlife Research Unit to become the Cooperative Units Program Supervisor for the South, replacing Dr. Kevin Whalen who took over as Supervisor for the West. We welcomed Dr. Sarah Converse who left the Patuxent Wildlife Research Center to become Leader of the Washington Cooperative Fish and Wildlife Research Unit. Dr. Amanda Rosenberger joined the Tennessee Cooperative Fishery Research Unit as Assistant Leader, transferring from the Missouri Cooperative Unit. Dr. Scott Carleton left his position as Assistant Unit Leader in New Mexico to become Chief of the Region 2 Migratory Bird Program of the U.S. Fish and Wildlife Service. We said farewell to many colleagues who retired. Their departure is bittersweet as we wish them health, happiness, and wellness in retirement. We will miss their companionship and the extraordinary contributions they have made to the Cooperative Fish and Wildlife Research Units Program and conservation. The Cooperative Fish and Wildlife Research Units Program has a record high number of vacant scientist positions due to a combination of retirements and base funding short-falls. These issues are affecting our ability to meet cooperator needs. Yet, we remain highly productive. For example, this year we released a report ( https://doi.org/10.3133/cir1427 ) containing abstracts of nearly 600 of our research projects, covering thematic areas ranging from advanced technologies to wildlife diseases. We provided highly competent, trained scientists and natural resource managers for our cooperators’ workforce. We delivered technical training and guidance to professional practitioners. We provided critical information to cooperators for decisions on species status assessments and management of species of greatest conservation need. This year we had an active presence at major national meetings, including the North American Wildlife and Natural Resources Conference where we co-sponsored a workshop on continuing education as a means to bridge the gap between science and management. During the coming year, with support from the U.S. Geological Survey and our cooperators, we intend to reduce the number of vacancies in the program. It will take time and active support of our cooperators to get back to full strength, but I am committed to this goal and encouraged by the resolve of our partners. We look forward to an even more productive year in 2018!

Circular↗

USGS2010

Social Values for Ecosystem Services (SolVES): using GIS to include social values information in ecosystem services assessments

Ecosystem services can be defined in various ways; simply put, they are the benefits provided by nature, which contribute to human well-being. These benefits can range from tangible products such as food and fresh water to cultural services such as recreation and esthetics. As the use of these benefits continues to increase, additional pressures are placed on the natural ecosystems providing them. This makes it all the more important when assessing possible tradeoffs among ecosystem services to consider the human attitudes and preferences that express underlying social values associated with their benefits. While some of these values can be accounted for through economic markets, other values can be more difficult to quantify, and attaching dollar amounts to them may not be very useful in all cases. Regardless of the processes or units used for quantifying such values, the ability to map them across the landscape and relate them to the ecosystem services to which they are attributed is necessary for effective assessments. To address some of the needs associated with quantifying and mapping social values for inclusion in ecosystem services assessments, scientists at the Rocky Mountain Geographic Science Center (RMGSC), in collaboration with Colorado State University, have developed a public domain tool, Social Values for Ecosystem Services (SolVES). SolVES is a geographic information system (GIS) application designed to use data from public attitude and preference surveys to assess, map, and quantify social values for ecosystem services. SolVES calculates and maps a 10-point Value Index representing the relative perceived social values of ecosystem services such as recreation and biodiversity for various groups of ecosystem stakeholders. SolVES output can also be used to identify and model relationships between social values and physical characteristics of the underlying landscape. These relationships can then be used to generate predicted Value Index maps for areas where survey data are not available. RMGSC will continue to develop more robust versions of SolVES by pursuing opportunities to work with land and resource managers as well as other researchers to apply SolVES to specific ecosystem management problems.

Fact Sheet↗

USGS1987

The geologic story of Yosemite National Park

Within 150 years, Yosemite has moved from great obscurity to worldwide fame as one of the most visited of our national parks. As a remarkable place where people can enjoy unparalleled scenes of natural beauty and where many easily observed geologic features are concentrated, the park is rivaled by few other areas on the planet. The majesty and immense variety of these features have inspired artists and photographers, intrigued tourists, and stirred controversy among geologists. Field studies in the Yosemite area have contributed to the development of our ideas about geologic processes, including the different actions of streams and glaciers in the evolution of the landscape, and the formation of granite, the basic bedrock of much of the Earth's continents. The park's role as a natural laboratory for geologic research cannot be overemphasized, and its investigation has led to many landmark studies by U.S. Geological Survey geologists over the past 70 years. In 1913, the first detailed program of research on the geology of the park and the origin ofYosemite Valley was begun by Francois Matthes and Frank Calkins. Their work, along with that of later generations of Survey geologists, myself included, serves as the basis for our present understanding of the geologic history of Yosemite and of the processes that formed and continue to mold its landscape. This book, which makes available in one volume a comprehensive summary of the current geologic knowledge of Yosemite National Park, is an excellent example of the Survey's continuing effort to provide earth-science information in the public service.

California↗

USGS2021

Evaluating the dynamics of groundwater, lakebed transport, nutrient inflow and algal blooms in Upper Klamath Lake, Oregon, USA

Transport of nutrients to lakes can occur via surface-water inflow, atmospheric deposition, groundwater (GW) inflow and benthic processes. Identifying and quantifying within-lake nutrient sources and recycling processes is challenging. Prior studies in hypereutrophic Upper Klamath Lake, Oregon, USA, indicated that ~60% of the early summer phosphorus (P) load to the lake was internal and hypothesized to be lakebed sediment release. Dynamic nutrient transport processes were examined to better characterize the nutrient sources. One-dimensional heat transport models calibrated to observed lakebed temperatures and a cross-sectional GW flow model provided estimates of GW-inflow rates that were greatest in spring and decreased through summer. One-dimensional solute transport models calibrated to observed lakebed pore-water dissolved silica (Si) and dissolved phosphate-phosphorus (DP) concentrations indicated that nutrients were transported from the lakebed by advection, diffusion, and enhanced mixing by benthic organisms and waves, and that DP removal occurred near the lakebed interface. Estimated water, Si, DP and total-phosphorus (TP) budgets indicated that GW contributed 21% of lake water inflow and at least 26, 20 and 16% of total Si, DP and TP inflow, respectively, when conservatively assuming background GW nutrient concentrations. However, lakebed GW (LGW) is enriched in nutrients during flow through lakebed sediment and the estimated GW contribution increased to 29 (33), 49 (67) and 43% (61%) of total Si, DP and TP inflow, respectively, if 20% (50%) of GW inflow to the lake was assumed to have LGW concentrations. Net nutrient inflow to the lake was greatest in spring and coincident with the annual diatom bloom. Inflowing dissolved nutrients appear to be assimilated by diatoms during the spring and become available for the summer Aphanizomenon flos-aquae bloom when the diatoms senesce. Thus, nutrient-enriched GW inflow and nutrient recycling by successive algal blooms must be considered when evaluating internal nutrient loading to lakes.

Oregon↗

USGS2023

Sources and chemical stability of soil organic carbon in natural and created coastal marshes of Louisiana

Coastal marshes are globally important for sequestering carbon, yet sea-level rise and anthropogenic stressors can reduce their capacity as carbon sinks. Marsh restoration can offset a portion of carbon loss through the degradation of natural marshes, but potential differences in the sources and stability of soil organic carbon (SOC) between created and natural marshes may affect their function as a long-term carbon sink. Here, we examine the sources and chemical stability of SOC in natural and created marshes across the Gulf coast of Louisiana, USA. Marshes were examined along an estuarine salinity gradient in a former interdistributary basin of the Mississippi River Delta and in six created marshes across a 32-year chronosequence and a natural reference marsh ( n = 6) in the Chenier Plain. Carbon source was assessed using δ 13 C analysis and chemical stability was determined through an acid hydrolysis digestion that removed labile carbon (LC). Soil δ 13 C values suggested that the local vegetation dominated SOC in all natural marshes although brackish marshes had a mix of sources and degradation of SOC. Recalcitrant carbon (RC) was 72.2 ± 0.5 % of SOC across fresh, brackish and saline marshes. The depth-averaged RC accumulation rate was almost three times greater than LC accumulation rate, yet both contributed significantly to accretion and long-term SOC accumulation (124–132 g m −2 y −1 in natural marshes). RC and SOC accumulation rate increased with mineral sediment accumulation rate. For the created marshes, SOC became increasingly recalcitrant due to an increase in in-situ plant inputs, but accumulation rates were lower than the natural marshes. Overall, this study illustrates that natural marshes have a large stock of RC from the vegetation while dredge sediment created marshes have no plant-derived carbon initially, which accumulates slowly thereafter. Restoration practices may be improved by preserving and augmenting these deteriorating but carbon-rich natural marshes.

Louisiana↗

USGS2024

Seasonally varying contributions of contemporaneous and lagged sources of instream total nitrogen and phosphorus load across the Illinois River basin

Quantifying nutrient sources in streams, their temporal and spatial variability, and drivers of that variability can support effective water resources management. Yet a lack of data and modeling capabilities has previously prevented comprehensive quantification across both space and time. Here a dynamic SPARROW (Spatially Referenced Regressions on Watershed attributes) model that accounts for a lagged delivery of nutrients to streams was developed and applied to simulate seasonal and source-specific total nitrogen (TN) and total phosphorus (TP) loads in streams across the Illinois River basin (IRB). Dynamic load predictions from 2000 through 2020 revealed that a third of the TN and a quarter of the TP instream load originated from non-point sources that were lagged in their delivery from land-application to streams by more than a season. This lagged mass was the largest overall TN source—which was estimated as a lagged expression of previous seasonal non-point sources including fertilizer, manure, atmospheric deposition and fixation, and urban land use. Treated wastewater effluent was the largest TP source exported from the basin, contributing 39 % of the TP load and 15 % of the TN load, and dominated the load in the upper Illinois River near Chicago. Loads in the lower river during this period, conversely, were attributed primarily to a mix of agricultural sources and their lagged fractions from headwater tributaries. Instream processes removed 10 % of the TN load while only 4 % of the TP load was removed during instream transport. With appropriate datasets, the models could be extended to other basins or time periods and used to forecast future seasonal nutrient loads.

Illinois↗

USGS2001

Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators

The sources of nitrate (NO-3) in groundwater of the shallow karst aquifer in southwestern Illinois' sinkhole plain were investigated using chemical and isotopic techniques. The groundwater in this aquifer is an important source of potable water for about half of the residents of the sinkhole plain area. Previous work has shown that groundwater from approximately 18% of the wells in the sinkhole plain has NO-3 concentrations in excess of the USEPA's drinking water standard of 10 mg N/1. Relative to background levels, the NO-3 concentrations in water from 52% of the wells, and probably all of the springs in the study area, are anomalously high, suggesting that sources other than naturally occurring soil organic matter have contributed additional NO-3 to groundwater in the shallow karst aquifer. This information, and the dominance of agriculture in the study area, suggest that agrichemical contributions may be significant. To test this hypothesis, water samples from 10 relatively large karst springs were collected during four different seasons and analyzed for inorganic constituents, dissolved organic carbon, atrazine, and ??15N and ??18O of the NO-3 ions. The isotopic data were most definitive and suggested that the sources of NO-3 in spring water are dominated by N-fertilizer with some possible influence of atmospheric NO-3 and, to a much lesser extent, human and/or animal waste. Differences in the isotopic composition of NO-3 and some of the chemical characteristics were observed during the four consecutive seasons in which spring water samples were collected. Isotopic values for ??15N and ??18O of the NO-3 ranged from 3.2??? to 19.1??? and from 7.2??? to 18.7???, respectively. The trend of ??15N and ??18O data for NO-3 also indicated that a significant degree of denitrification is occurring in the shallow karst hydrologic system (within the soil zone, the epikarst and the shallow karst aquifer) prior to discharging to springs. ?? 2001 Elsevier Science B.V. All rights reserved.

Chemical Geology↗

USGS2017

Soil Seed Bank Responses to Postfire Herbicide and Native Seeding Treatments Designed to Control Bromus tectorum in a Pinyon–Juniper Woodland at Zion National Park, USA

The continued threat of an invasive, annual brome ( Bromus ) species in the western United States has created the need for integrated approaches to postfire restoration. Additionally, the high germination rate, high seed production, and seed bank carryover of annual bromes points to the need to assay soil seed banks as part of monitoring programs. We sampled the soil seed bank to help assess the effectiveness of treatments utilizing the herbicide Plateau® (imazapic) and a perennial native seed mix to control annual Bromus species and enhance perennial native plant establishment following a wildfire in Zion National Park, Utah. This study is one of few that have monitored the effects of imazapic and native seeding on a soil seed bank community and the only one that we know of that has done so in a pinyon–juniper woodland. The study made use of untreated, replicated controls, which is not common for seed bank studies. One year posttreatment, Bromus was significantly reduced in plots sprayed with herbicide. By the second year posttreatment, the effects of imazapic were less evident and convergence with the controls was evident. Emergence of seeded species was low for the duration of the study. Dry conditions and possible interactions with imazapic probably contributed to the lack of emergence of seeded native species. The perennial grass sand dropseed outperformed the other species included in the seed mix. We also examined how the treatments affected the soil seed bank community as a whole. We found evidence that the herbicide was reducing several native annual forbs and one nonnative annual forb. However, overall effects on the community were not significant. The results of our study were similar to what others have found in that imazapic is effective in providing a short-term reduction in Bromus density, although it can impact emergence of nontarget species.

Utah↗