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At least 307 records · Page 17Linked to original sources
USGS2016

Selected streambed sediment compounds and water toxicity results for Westside Creeks, San Antonio, Texas, 2014

Introduction The Alazán, Apache, Martínez, and San Pedro Creeks in San Antonio, Texas, are part of a network of urban tributaries to the San Antonio River, known locally as the Westside Creeks. The Westside Creeks flow through some of the oldest neighborhoods in San Antonio. The disruption of streambed sediment is anticipated during a planned restoration to improve and restore the environmental condition of 14 miles of channelized sections of the Westside Creeks in San Antonio. These construction activities can create the potential to reintroduce chemicals found in the sediments into the ecosystem where, depending on hydrologic and environmental conditions, they could become bioavailable and toxic to aquatic life. Elevated concentrations of sediment-associated contaminants often are measured in urban areas such as San Antonio, Tex. Contaminants found in sediment can affect the health of aquatic organisms that ingest sediment. The gradual accumulation of trace elements and organic compounds in aquatic organisms can cause various physiological issues and can ultimately result in death of the aquatic organisms; in addition, subsequent ingestion of aquatic organisms can transfer the accumulated contaminants upward through the food chain (a process called biomagnification). The U.S. Geological Survey, in cooperation with the San Antonio River Authority, collected sediment samples and water samples for toxicity testing from sites on the Westside Creeks as part of an initial characterization of selected contaminants in the study area. Samples were collected in January 2014 during base-flow conditions and again in May 2104 after a period of stormwater runoff (poststorm conditions). Sediment samples were analyzed for selected constituents, including trace elements and organic contaminants such as pesticides, brominated flame retardants, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). In addition, as an indicator of ecological health (and possibly bioavailability of contaminants in disturbed streambed sediments), the toxicity of water samples to the indicator species Pimephales promelas (fathead minnow) was evaluated by using standard 7-day water-toxicity testing.

Texas↗
USGS2009

Fires and landscape conservation in mediterranean ecosystems

Protected areas are some of the last remaining areas on Earth where fire can play its natural role at a landscape-scale. The International Union for Conservation of Nature (IUCN) has developed a system for categorizing protected areas. The role fire can play in the various categories depends on the management objectives of the category, the size of the individual units, and the laws and policies of the country in which the unit is located. An analysis of all the IUCN protected areas showed that 505 areas had the potential for conserving landscape fire. Areas in Europe, Africa, South America, Australia, and North America show promise for being able to include fire in the conservation of landscapes. Examples from South Africa, Australia, and the United States show how fire can be incorporated at the landscape scale. Future challenges include increasing urban encroachment, climate change, and air pollution. Society will have to deal with these challenges if fire is to continue its essential ecological role in Mediterranean ecosystems.

Book chapter↗
USGS2017

Increasing floodplain connectivity through urban stream restoration increases nutrient and sediment retention

Stream restoration practices frequently aim to increase connectivity between the stream channel and its floodplain to improve channel stability and enhance water quality through sediment trapping and nutrient retention. To measure the effectiveness of restoration and to understand the drivers of these functional responses, we monitored five restored urban streams that represent a range of channel morphology and restoration ages. High and low elevation floodplain plots were established in triplicate in each stream to capture variation in floodplain connectivity. We measured ecosystem geomorphic and soil attributes, sediment and nutrient loading, and rates of soil nutrient biogeochemistry processes (denitrification; N and P mineralization) then used boosted regression trees (BRT) to identify controls on sedimentation and nutrient processing. Local channel and floodplain morphology and position within the river network controlled connectivity with increased sedimentation at sites downstream of impaired reaches and at floodplain plots near the stream channel and at low elevations. We observed that nitrogen loading (both dissolved and particulate) was positively correlated with denitrification and N mineralization and dissolved phosphate loading positively influenced P mineralization; however, none of these input rates or transformations differed between floodplain elevation categories. Instead, continuous gradients of connectivity were observed rather than categorical shifts between inset and high floodplains. Organic matter and nutrient content in floodplain soils increased with the time since restoration, which highlights the importance of recovery time after construction that is needed for restored systems to increase ecosystem functions. Our results highlight the importance of restoring floodplains downstream of sources of impairment and building them at lower elevations so they flood frequently, not just during bankfull events. This integrated approach has the greatest potential for increasing trapping of sediment, nutrients, and associated pollutants in restored streams and thereby improving water quality in urban watersheds.

North Carolina↗
USGS2011

Tools and methods for evaluating and refining alternative futures for coastal ecosystem management—the Puget Sound Ecosystem Portfolio Model

The U.S. Geological Survey Puget Sound Ecosystem Portfolio Model (PSEPM) is a decision-support tool that uses scenarios to evaluate where, when, and to what extent future population growth, urban growth, and shoreline development may threaten the Puget Sound nearshore environment. This tool was designed to be used iteratively in a workshop setting in which experts, stakeholders, and decisionmakers discuss consequences to the Puget Sound nearshore within an alternative-futures framework. The PSEPM presents three possible futures of the nearshore by analyzing three growth scenarios developed out to 2060: Status Quo—continuation of current trends; Managed Growth—adoption of an aggressive set of land-use management policies; and Unconstrained Growth—relaxation of land-use restrictions. The PSEPM focuses on nearshore environments associated with barrier and bluff-backed beaches—the most dominant shoreforms in Puget Sound—which represent 50 percent of Puget Sound shorelines by length. This report provides detailed methodologies for development of three submodels within the PSEPM—the Shellfish Pollution Model, the Beach Armoring Index, and the Recreation Visits Model. Results from the PSEPM identify where and when future changes to nearshore ecosystems and ecosystem services will likely occur within the three growth scenarios. Model outputs include maps that highlight shoreline sections where nearshore resources may be at greater risk from upland land-use changes. The background discussed in this report serves to document and supplement model results displayed on the PSEPM Web site located at http://geography.wr.usgs.gov/pugetSound/.

Washington↗
USGS2018

What goes up must come down: Integrating air and water quality monitoring for nutrients

Excess nitrogen and phosphorus (“nutrients”) loadings continue to affect ecosystem function and human health across the U.S. Our ability to connect atmospheric inputs of nutrients to aquatic end points remains limited due to uncoupled air and water quality monitoring. Where connections exist, the information provides insights about source apportionment, trends, risk to sensitive ecosystems, and efficacy of pollution reduction efforts. We examine several issues driving the need for better integrated monitoring, including: coastal eutrophication, urban hotspots of deposition, a shift from oxidized to reduced nitrogen deposition, and the disappearance of pristine lakes. Successful coordination requires consistent data reporting; collocating deposition and water quality monitoring; improving phosphorus deposition measurements; and filling coverage gaps in urban corridors, agricultural areas, undeveloped watersheds, and coastal zones.

Environmental Science and Technology↗
USGS2011

Restoring and rehabilitating sagebrush habitats

Less than half of the original habitat of the Greater Sage-Grouse (Centrocercus uropha-sianus) currently exists. Some has been perma-nently lost to farms and urban areas, but the remaining varies in condition from high quality to no longer adequate. Restoration of sagebrush (Artemisia spp.) grassland ecosystems may be pos-sible for resilient lands. However, Greater Sage-Grouse require a wide variety of habitats over large areas to complete their life cycle. Effective restoration will require a regional approach for prioritizing and identifying appropriate options across the landscape. A landscape triage method is recommended for prioritizing lands for restora-tion. Spatial models can indicate where to protect and connect intact quality habitat with other simi-lar habitat via restoration. The ecological site con-cept of land classification is recommended for characterizing potential habitat across the region along with their accompanying state and transi-tion models of plant community dynamics. These models assist in identifying if passive, manage-ment-based or active, vegetation manipulation?based restoration might accomplish the goals of improved Greater Sage-Grouse habitat. A series of guidelines help formulate questions that manag-ers might consider when developing restoration plans: (1) site prioritization through a landscape triage; (2) soil verification and the implications of soil features on plant establishment success; (3) a comparison of the existing plant community to the potential for the site using ecological site descriptions; (4) a determination of the current successional status of the site using state and transition models to aid in predicting if passive or active restoration is necessary; and (5) implemen-tation of post-treatment monitoring to evaluate restoration effectiveness and post-treatment man-agement implications to restoration success.

Book chapter↗
USGS2009

Nitrate removal in stream ecosystems measured by 15 N addition experiments: Total uptake

We measured uptake length of 15 NO- 3 in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO- 3 uptake length. As part of the Lotic Intersite Nitrogen eXperiment II project, we chose nine streams in each region corresponding to natural (reference), suburban-urban, and agricultural land uses. Study streams spanned a range of human land use to maximize variation in NO- 3 concentration, geomorphology, and metabolism. We tested a causal model predicting controls on NO- 3 uptake length using structural equation modeling. The model included concomitant measurements of ecosystem metabolism, hydraulic parameters, and nitrogen concentration. We compared this structural equation model to multiple regression models which included additional biotic, catchment, and riparian variables. The structural equation model explained 79% of the variation in log uptake length (S Wtot ). Uptake length increased with specific discharge (Q/w) and increasing NO- 3 concentrations, showing a loss in removal efficiency in streams with high NO- 3 concentration. Uptake lengths shortened with increasing gross primary production, suggesting autotrophic assimilation dominated NO- 3 removal. The fraction of catchment area as agriculture and suburban-urban land use weakly predicted NO- 3 uptake in bivariate regression, and did improve prediction in a set of multiple regression models. Adding land use to the structural equation model showed that land use indirectly affected NO- 3 uptake lengths via directly increasing both gross primary production and NO- 3 concentration. Gross primary production shortened S Wtot , while increasing NO- 3 lengthened S Wtot resulting in no net effect of land use on NO- 3 removal. ?? 2009.

Limnology and Oceanography↗
USGS2003

Ecosystem history of southern and central Biscayne Bay: Summary report on sediment core analyses

During the last century, the environs of Biscayne Bay have been greatly affected by anthropogenic alteration through urbanization of the Miami/Dade County area. The sources, timing, delivery, and quality of freshwater flow into the Bay have been changed by construction of a complex canal system that controls movement of water throughout south Florida. Changes in shoreline and sub-aquatic vegetation and marine organisms have been observed and changes in water delivery are believed to be the cause. Current restoration goals are attempting to restore natural flow of fresh water into Biscayne and Florida Bays and to restore the natural fauna and flora, but first we need to determine pre-alteration baseline conditions in order to establish targets and performance measures for restoration. This research is part of an ongoing study designed to address the needs of the Biscayne Bay Coastal Wetlands Project (BBCW) of the Comprehensive Everglades Restoration Plan (CERP). By establishing the natural patterns of temporal change in salinity, water quality, vegetation, and benthic fauna in Biscayne Bay and the nearby wetlands over the last 100- 500 years the USGS, in collaboration with our partners, will provide the data necessary to set realistic targets to achieve the BBCW Project goals. Six cores from three sites in Biscayne Bay were collected in April 2002 for multidisciplinary multi-proxy analyses. This report details the results of these analyses and compares the 2002 cores to cores collected in 1997. The following are our significant findings to date: The salinity of central Biscayne Bay has become increasingly marine and increasingly stable over the last 100 years. At No Name Bank, prior to approximately 1915, the inter-decadal and decadal salinity fluctuations appear to have been greater than after 1915 when salinities stabilized at that site. Continental shelf/open marine influence on the sites has increased during the 20th century. There is no indication of inter-decadal salinity extremes or periods of hypersalinity. Freshwater and mesohaline salinities have had a minor influence on No Name bank throughout the time of deposition. At Featherbed Bank, the influence is reduced to mesohaline salinities. Card Bank has experienced relatively large swings in salinity over multi-decadal and centennial timescales, compared to central Biscayne Bay, but marine influence at the site has increased over the last century. Indications of regional scale patterns have been found, especially in the shell chemistry data and the pollen assemblages. These regional patterns indicate that the changes are not site specific and may not be limited to Biscayne Bay. Sub-aquatic vegetation has undergone bay-wide patterns of change over the last 200-500 years, which includes expansion prior to 1900 and declines during the last century in central Biscayne Bay. Thalassia appears to have increased at all three core sites sometime between 1550 and 1750 AD. A decline in Thalassia appears to have occurred after 1950 at No Name Bank and slightly earlier in the 20th century at Featherbed Bank. Card Bank does not appear to have experienced any declines in vegetation on an inter-decadal scale during the 20th century. Molluscan faunal abundance and diversity have undergone significant changes in central Biscayne Bay. Indicators of increased organic-rich sediments at No Name occur between 1869 to 1888 and between the 1930’s to 1975. These changes may correlate to human activities (settlement, population growth). These findings represent a first step towards the project’s goal to reconstruct the history of Biscayne Bay and they provide us with a working model to be tested at other sites. It is clear from our findings that Biscayne Bay has been a dynamic environment over the last 500 years, with natural changes occurring in salinity and benthic habitats. However, several significant changes have occurred in the 20th century: 1) increased stabilization of marine salinities; 2) declines in seagrass in central Biscayne Bay; 3) dramatic changes in molluscan abundance and diversity in central Biscayne Bay. The question remains - how do we better differentiate natural cycles of change from anthropogenic change within these observed trends? The preliminary implications from our research are that changes in salinity and benthic habitats have occurred naturally in Biscayne Bay on inter-decadal to centennial scales, perhaps due to climatic changes, changes in sea level, bank migrations, or a combination of factors. However, further work needs to be done to determine which components of change in the 20th century are human-induced and which are natural. By examining the historical records preserved in the sediments of Biscayne Bay, we can provide restoration trust agencies with the information necessary to set realistic targets and performance measures for Biscayne Bay.

Florida↗
USGS2009

Nitrate removal in stream ecosystems measured by 15 N addition experiments: Denitrification

We measured denitrification rates using a field 15 N-NO- 3 tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (S Wden ) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N 2 production rates far exceeded N 2 O production rates in all streams. The fraction of total NO- 3 removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NHz 4 concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling S Wden were specific discharge (discharge / width) and NO- 3 concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (U den ) and NO- 3 concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although Uden increased with increasing NO- 3 concentration, the efficiency of NO- 3 removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO- 3 load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO- 3 concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO- 3 concentration. ?? 2009.

Limnology and Oceanography↗
USGS2021

Developing a set of indicators to identify, monitor, and track impacts and change in forests of the United States

United States forestland is an important ecosystem type, land cover, land use, and economic resource that is facing several drivers of change including climatic. Because of its significance, forestland was identified through the National Climate Assessment (NCA) as a key sector and system of concern to be included in a system of climate indicators as part of a sustained assessment effort. Here, we describe 11 informative core indicators of forests and climate change impacts with metrics available or nearly available for use in the NCA efforts. The recommended indicators are based on a comprehensive conceptual model which recognizes forests as a land use, an ecosystem, and an economic sector. The indicators cover major forest attributes such as extent, structural components such as biomass, functions such as growth and productivity, and ecosystem services such as biodiversity and outdoor recreation. Interactions between humans and forests are represented through indicators focused on the wildland-urban interface, cost to mitigate wildfire risk, and energy produced from forest-based biomass. Selected indicators also include drought and disturbance from both wildfires and biotic agents. The forest indicators presented are an initial set that will need further refinement in coordination with other NCA indicator teams. Our effort ideally will initiate the collection of critical measurements and observations and lead to additional research on forest-climate indicators.

Climatic Change↗
USGS2016

Freshwater wrack along Great Lakes coasts harbors Escherichia coli: Potential for bacterial transfer between watershed environments

We investigated the occurrence, persistence, and growth potential of Escherichia coli associated with freshwater organic debris (i.e., wrack) frequently deposited along shorelines (shoreline wrack), inputs from rivers (river CPOM), and parking lot runoffs (urban litter). Samples were collected from 9 Great Lakes beaches, 3 creeks, and 4 beach parking lots. Shoreline wrack samples were mainly composed of wood chips, straw, sticks, leaf litter, seeds, feathers, and mussel shells; creek and parking lot samples included dry grass, straw, seeds, wood chips, leaf/pine needle litter; soil particles were present in parking lot samples only. E. coli concentrations (most probable number, MPN) were highly variable in all sample types: shoreline wrack frequently reached 10 5 /g dry weight (dw), river CPOM ranged from 81 to 7,916/g dw, and urban litter ranged from 0.5 to 24,952/g dw. Sequential rinsing studies showed that 61–87% of E. coli concentrations were detected in the first wash of shoreline wrack, with declining concentrations associated with 4–8 subsequent washings; viable counts were still detected even after 8 washes. E. coli grew readily in shoreline wrack and river CPOM incubated at 35 °C. At 30°C, growth was only detected in river CPOM and not in shoreline wrack or urban litter, but the bacteria persisted for at least 16 days. In summary, freshwater wrack is an understudied component of the beach ecosystem that harbors E. coli and thus likely influences estimations of water quality and the microbial community in the nearshore as a result of transfer between environments.

Illinois, Indiana, Ontario↗
USGS2024

Intra-urban variations in land surface phenology in a semi-arid environment

Urban vegetation is growing in importance as cities use 'green infrastructure' to mitigate the impacts of climate change, reduce extreme heat, and improve human health and comfort. However, due to the heterogeneity of city landscapes, urban vegetation experiences a diverse range of environmental conditions, potentially leading to differences in growing season timing and length within cities. Here, we investigate physical drivers of urban land surface phenology and timing within a semi-arid city (Denver, CO, USA) using four years (2018–2021) of remotely sensed vegetation indices, modelled air temperature, and land cover datasets. Within the metropolitan region study area, satellite-based vegetation index measurements indicate that growing season length is variable on sub-neighborhood spatial scales. This variability is largely due to differences in the timing of fall senescence, as opposed to early season growth. Areas with substantial fractions of irrigated land cover tend to remain greener for longer, while unirrigated and cooler areas are correlated with an earlier end to the growing season (up to ∼two months shorter). These findings complement those from non-arid cities where surface and air temperature are the dominant environmental control on phenological timing. Results here indicate the importance of soil moisture for phenology in semi-arid regions and suggest unique semi-arid urban growing season dynamics and temperature-vegetation feedbacks. These interactions have implications for water, heat, and vegetation management strategies to maximize ecosystem services in water-limited environments.

Colorado↗
USGS2017

A mosaic-based approach is needed to conserve biodiversity in disturbed freshwater ecosystems

Conserving native biodiversity in the face of human‐ and climate‐related impacts is a challenging and globally important ecological problem that requires an understanding of spatially connected, organismal‐habitat relationships. Globally, a suite of disturbances (e.g., agriculture, urbanization, climate change) degrades habitats and threatens biodiversity. A mosaic approach (in which connected, interacting collections of juxtaposed habitat patches are examined) provides a scientific foundation for addressing many disturbance‐related, ecologically based conservation problems. For example, if specific habitat types disproportionately increase biodiversity, these keystones should be incorporated into research and management plans. Our sampling of fish biodiversity and aquatic habitat along ten 3‐km sites within the Upper Neosho River subdrainage, KS, from June‐August 2013 yielded three generalizable ecological insights. First, specific types of mesohabitat patches (i.e., pool, riffle, run, and glide) were physically distinct and created unique mosaics of mesohabitats that varied across sites. Second, species richness was higher in riffle mesohabitats when mesohabitat size reflected field availability. Furthermore, habitat mosaics that included more riffles had greater habitat diversity and more fish species. Thus, riffles (<5% of sampled area) acted as keystone habitats. Third, additional conceptual development, which we initiate here, can broaden the identification of keystone habitats across ecosystems and further operationalize this concept for research and conservation. Thus, adopting a mosaic approach can increase scientific understanding of organismal‐habitat relationships, maintain natural biodiversity, advance spatial ecology, and facilitate effective conservation of native biodiversity in human‐altered ecosystems.

Kansas↗
USGS2016

Spatial and temporal variability of contaminants within estuarine sediments and native Olympia oysters: A contrast between a developed and an undeveloped estuary

Chemical contaminants can be introduced into estuarine and marine ecosystems from a variety of sources including wastewater, agriculture and forestry practices, point and non-point discharges, runoff from industrial, municipal, and urban lands, accidental spills, and atmospheric deposition. The diversity of potential sources contributes to the likelihood of contaminated marine waters and sediments and increases the probability of uptake by marine organisms. Despite widespread recognition of direct and indirect pathways for contaminant deposition and organismal exposure in coastal systems, spatial and temporal variability in contaminant composition, deposition, and uptake patterns are still poorly known. We investigated these patterns for a suite of persistent legacy contaminants including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) and chemicals of emerging concern including pharmaceuticals within two Oregon coastal estuaries (Coos and Netarts Bays). In the more urbanized Coos Bay, native Olympia oyster ( Ostrea lurida ) tissue had approximately twice the number of PCB congeners at over seven times the total concentration, yet fewer PBDEs at one-tenth the concentration as compared to the more rural Netarts Bay. Different pharmaceutical suites were detected during each sampling season. Variability in contaminant types and concentrations across seasons and between species and media (organisms versus sediment) indicates the limitation of using indicator species and/or sampling annually to determine contaminant loads at a site or for specific species. The results indicate the prevalence of legacy contaminants and CECs in relatively undeveloped coastal environments highlighting the need to improve policy and management actions to reduce contaminant releases into estuarine and marine waters and to deal with legacy compounds that remain long after prohibition of use. Our results point to the need for better understanding of the ecological and human health risks of exposure to the diverse cocktail of pollutants and harmful compounds that will continue to leach from estuarine sediments over time.

Oregon↗
USGS2021

Inclusion of pesticide transformation products is key to estimating pesticide exposures and effects in small U.S. streams

Improved analytical methods can quantify hundreds of pesticide transformation products (TPs), but understanding of TP occurrence and potential toxicity in aquatic ecosystems remains limited. We quantified 108 parent pesticides and 116 TPs in more than 3 700 samples from 442 small streams in mostly urban basins across five major regions of the United States. TPs were detected nearly as frequently as parents (90 and 95% of streams, respectively); 102 TPs were detected at least once and 28 were detected in >20% samples in at least one region—TPs of 9 herbicides, 2 fungicides (chlorothalonil and thiophanate-methyl), and 1 insecticide (fipronil) were the most frequently detected. TPs occurred commonly during baseflow conditions, indicating chronic environmental TP exposures to aquatic organisms and the likely importance of groundwater as a TP source. Hazard quotients based on acute aquatic-life benchmarks for invertebrates and nonvascular plants and vertebrate-centric molecular endpoints (sublethal effects) quantify the range of the potential contribution of TPs to environmental risk and highlight several TP exposure–response data gaps. A precautionary approach using equimolar substitution of parent benchmarks or endpoints for missing TP benchmarks indicates that potential aquatic effects of pesticide TPs could be underestimated by an order of magnitude or more.

Environmental Science and Technology↗
USGS2020

Understanding the relationship between stream metabolism and biological assemblages

Biological assemblages are commonly used for assessing stream health, but there is increased interest among the freshwater research community in incorporating measures of stream function, such as metabolism, to strengthen stream-health assessments. Presently, there is limited information about the relationships between stream metabolism and biological assemblages, along with the measurement period required to relate metabolism with stream biota. Our study assessed which environmental factors explained stream metabolism and to what degree stream metabolism and minimum dissolved oxygen (DOmin) were related to invertebrate and fish metrics in streams distributed across several regions of the United States. Furthermore, we evaluated the number of metabolism monitoring days required for maximizing the ability to detect relationships between stream metabolism and biological assemblage metrics. We sampled 17 sites distributed among reference, agricultural, and urban areas for stream metabolism, nutrients, habitat, and biological assemblages (invertebrates and fishes). Overall, sites were heterotrophic with gross primary production (GPP) and ecosystem respiration (ER) related primarily to days since last high flow, canopy cover, maximum water temperature, and total phosphorus. DOmin was related to days since last high flow, canopy cover, and maximum water temperature. We were unable to determine a clear statistical relationship between invertebrate metrics (invertebrate richness; Ephemeroptera, Plecoptera, and Trichoptera richness; and scraper-taxa richness) and GPP, ER, or DOmin. In contrast, we found that 2 fish-assemblage metrics were associated with stream metabolism and DOmin. A fish multimetric index (FMMI) was negatively correlated with GPP ( r = −0.5, p = 0.048) and positively correlated with DOmin ( r = 0.47, p = 0.06). Percentage of omnivorous fish taxa was positively correlated with GPP ( r = 0.72, p = 0.001) and ER ( r = 0.55, p = 0.02) and negatively correlated with DOmin ( r = −0.67, p = 0.003). The lack of detected relationships for most of the biological-assemblage metrics with stream metabolism may be partially due to 1 or more factors, including high variability, low sample size, limited range in metabolism values, assemblage metrics used, and geographic distribution of sites. Comparing stream-metabolism measurement periods (in days) to biological-assemblage metrics indicated that optimum correlations occurred at 2 d for DOmin, 3 d for GPP, and 14 d for ER. Although our study found limited relationships of stream metabolism and DOmin with biological assemblages, future studies should consider a larger sample size (≥30), 14-d or longer metabolism measurement period, and assessment of other taxa-specific or assemblage metrics.

Freshwater Science↗
USGS2003

Nitrogen emissions, deposition, and monitoring in the Western United States

Nitrogen (N) deposition in the western United States ranges from 1 to 4 kilograms (kg) per hectare (ha) per year over much of the region to as high as 30 to 90 kg per ha per year downwind of major urban and agricultural areas. Primary N emissions sources are transportation, agriculture, and industry. Emissions of N as ammonia are about 50% as great as emissions of N as nitrogen oxides. An unknown amount of N deposition to the West Coast originates from Asia. Nitrogen deposition has increased in the West because of rapid increases in urbanization, population, distance driven, and large concentrated animal feeding operations. Studies of ecological effects suggest that emissions reductions are needed to protect sensitive ecosystem components. Deposition rates are unknown for most areas in the West, although reasonable estimates are available for sites in California, the Colorado Front Range, and central Arizona. National monitoring networks provide long-term wet deposition data and, more recently, estimated dry deposition data at remote sites. However, there is little information for many areas near emissions sources.

BioScience↗
USGS2017

Restoration of contaminated ecosystems: adaptive management in a changing climate

Three case studies illustrate how adaptive management (AM) has been used in ecological restorations that involve contaminants. Contaminants addressed include mercury, selenium, and contaminants and physical disturbances delivered to streams by urban stormwater runoff. All three cases emphasize the importance of broad stakeholder input early and consistently throughout decision analysis for AM. Risk of contaminant exposure provided input to the decision analyses (e.g. selenium exposure to endangered razorback suckers, Stewart Lake; multiple contaminants in urban stormwater runoff, Melbourne) and was balanced with the protection of resources critical for a desired future state (e.g. preservation old growth trees, South River). Monitoring also played a critical role in the ability to conduct the decision analyses necessary for AM plans. For example, newer technologies in the Melbourne case provided a testable situation where contaminant concentrations and flow disturbance were reduced to support a return to good ecological condition. In at least one case (Stewart Lake), long-term monitoring data are being used to document the potential effects of climate change on a restoration trajectory. Decision analysis formalized the process by which stakeholders arrived at the priorities for the sites, which together constituted the desired future condition towards which each restoration is aimed. Alternative models were developed that described in mechanistic terms how restoration can influence the system towards the desired future condition. Including known and anticipated effects of future climate scenarios in these models will make them robust to the long-term exposure and effects of contaminants in restored ecosystems.

Restoration Ecology↗