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At least 595 records · Page 33Linked to original sources
USGS2008

Variability in Lotic Communities in Three Contrasting Stream Environments in the Santa Ana River Basin, California, 1999-2001

Biotic communities and environmental conditions can be highly variable between natural ecosystems. The variability of natural assemblages should be considered in the interpretation of any ecological study when samples are either spatially or temporally distributed. Little is known about biotic variability in the Santa Ana River Basin. In this report, the lotic community and habitat assessment data from ecological studies done as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program are used for a preliminary assessment of variability in the Santa Ana Basin. Habitat was assessed, and benthic algae, benthic macroinvertebrate, and fish samples were collected at four sites during 1999-2001. Three of these sites were sampled all three years. One of these sites is located in the San Bernardino Mountains, and the other two sites are located in the alluvial basin. Analysis of variance determined that the three sites with multiyear data were significantly different for 41 benthic algae metrics and 65 macroinvertebrate metrics and fish communities. Coefficients of variation (CVs) were calculated for the habitat measurements, metrics of benthic algae, and macroinvertebrate data as measures of variability. Annual variability of habitat data was generally greater at the mountain site than at the basin sites. The mountain site had higher CVs for water temperature, depth, velocity, canopy angle, streambed substrate, and most water-quality variables. In general, CVs of most benthic algae metrics calculated from the richest-targeted habitat (RTH) samples were greater at the mountain site. In contrast, CVs of most benthic algae metrics calculated from depositional-targeted habitat (DTH) samples were lower at the mountain site. In general, CVs of macroinvertebrate metrics calculated from qualitative multihabitat (QMH) samples were lower at the mountain site. In contrast, CVs of many metrics calculated from RTH samples were greater at the mountain site than at one of the basin sites. Fish communities were more variable at the basin sites because more species were present at these sites. Annual variability of benthic algae metrics was related to annual variability in habitat variables. The CVs of benthic algae metrics related to the most CVs of habitat variables included QMH taxon richness, the RTH percentage richness, RTH abundance of tolerant taxa, RTH percentage richness of halophilic diatoms, RTH percentage abundance of sestonic diatoms, DTH percentage richness of nitrogen heterotrophic diatoms, and DTH pollution tolerance index. The CVs of macroinvertebrate metrics related to the most CVs of habitat variables included the RTH trichoptera, RTH EPT, RTH scraper richness, RTH nonchironomid dipteran abundance (in percent), and RTH EPA (U.S. Environmental Protection Agency) tolerance, which is based on abundance. Many of the CVs of habitat variables related to CVs of macroinvertebrate metrics were the same habitat variables that were related to the CVs of benthic algae metrics. On the basis of these results, annual variability may have a role in the relationship of benthic algae and macroinvertebrates assemblages with habitat and water quality in the Santa Ana Basin. This report provides valuable baseline data on the variability of biological communities in the Santa Ana Basin.

Scientific Investigations Report↗
USGS2015

Pathway-based approaches for assessment of real-time exposure to an estrogenic wastewater treatment plant effluent on fathead minnow reproduction

Wastewater treatment plant (WWTP) effluents are known contributors of chemical mixtures into the environment. Of particular concern are endocrine-disrupting compounds, such as estrogens, which can affect the hypothalamic-pituitary-gonadal axis function in exposed organisms. The present study examined reproductive effects in fathead minnows exposed for 21 d to a historically estrogenic WWTP effluent. Fathead minnow breeding pairs were held in control water or 1 of 3 effluent concentrations (5%, 20%, and 100%) in a novel onsite, flow-through system providing real-time exposure. The authors examined molecular and biochemical endpoints representing key events along adverse outcome pathways linking estrogen receptor activation and other molecular initiating events to reproductive impairment. In addition, the authors used chemical analysis of the effluent to construct a chemical-gene interaction network to aid in targeted gene expression analyses and identifying potentially impacted biological pathways. Cumulative fecundity was significantly reduced in fish exposed to 100% effluent but increased in those exposed to 20% effluent, the approximate dilution factor in the receiving waters. Plasma vitellogenin concentrations in males increased in a dose-dependent manner with effluent concentration; however, male fertility was not impacted. Although in vitro analyses, analytical chemistry, and biomarker responses confirmed the effluent was estrogenic, estrogen receptor agonists were unlikely the primary driver of impaired reproduction. The results provide insights into the significance of pathway-based effects with regard to predicting adverse reproductive outcomes.

Environmental Toxicology and Chemistry↗
USGS2010

Surface-water quantity and quality, aquatic biology, stream geomorphology, and groundwater-flow simulation for National Guard Training Center at Fort Indiantown Gap, Pennsylvania, 2002-05

Base-line and long-term monitoring of water resources of the National Guard Training Center at Fort Indiantown Gap in south-central Pennsylvania began in 2002. Results of continuous monitoring of streamflow and turbidity and monthly and stormflow water-quality samples from two continuous-record long-term stream sites, periodic collection of water-quality samples from five miscellaneous stream sites, and annual collection of biological data from 2002 to 2005 at 27 sites are discussed. In addition, results from a stream-geomorphic analysis and classification and a regional groundwater-flow model are included. Streamflow at the facility was above normal for the 2003 through 2005 water years and extremely high-flow events occurred in 2003 and in 2004. Water-quality samples were analyzed for nutrients, sediments, metals, major ions, pesticides, volatile and semi-volatile organic compounds, and explosives. Results indicated no exceedances for any constituent (except iron) above the primary and secondary drinking-water standards or health-advisory levels set by the U.S. Environmental Protection Agency. Iron concentrations were naturally elevated in the groundwater within the watershed because of bedrock lithology. The majority of the constituents were at or below the method detection limit. Sediment loads were dominated by precipitation due to the remnants of Hurricane Ivan in September 2004. More than 60 percent of the sediment load measured during the entire study was transported past the streamgage in just 2 days during that event. Habitat and aquatic-invertebrate data were collected in the summers of 2002-05, and fish data were collected in 2004. Although 2002 was a drought year, 2003-05 were above-normal flow years. Results indicated a wide diversity in invertebrates, good numbers of taxa (distinct organisms), and on the basis of a combination of metrics, the majority of the 27 sites indicated no or slight impairment. Fish-metric data from 25 sites indicated results similar to the invertebrate data. Stream classification based on evolution of the stream channels indicates about 94 percent of the channels were considered to be in equilibrium (type B or C channels), neither aggrading nor eroding. A regional, uncalibrated groundwater-flow model indicated the surface-water and groundwater-flow divides coincided. Because of folding of rock layers, groundwater was under confined conditions and nearly all the water leaves the facility via the streams.

Scientific Investigations Report↗
USGS2017

Design and methods of the Pacific Northwest Stream Quality Assessment (PNSQA), 2015

In 2015, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) project conducted the Pacific Northwest Stream Quality Assessment (PNSQA) to investigate stream quality across the western part of the Pacific Northwest. The goal of the PNSQA was to assess the health of streams in the region by characterizing multiple water-quality factors that are stressors to in-stream aquatic life and by evaluating the relation between these stressors and the condition of biological communities. The effects of urbanization and agriculture on stream quality for the Puget Lowland and Willamette Valley Level III Ecoregions were the focus of this regional study. Findings will help inform the public and policymakers about human and environmental factors that are the most critical in affecting stream quality and, thus, provide insights into possible strategies to protect or improve the health of streams in the region. Land-use data were used in the study to identify and select sites within the region that ranged in levels of urban and agricultural development. A total of 88 sites were selected across the region—69 were on streams that explicitly spanned a range of urban land use in their watersheds, 8 were on streams in agricultural watersheds, and 11 were reference sites with little or no development in their watersheds. Depending on the type of land use, sites were sampled for contaminants, nutrients, and sediment for either a 4- or 10-week period during April, May, and June 2015. This water-quality “index period” was immediately followed with an ecological survey of all sites that included stream habitat, benthic algae, benthic macroinvertebrates, and fish. Additionally, streambed sediment was collected during the ecological survey for analysis of sediment chemistry and toxicity testing. This report provides a detailed description of the specific study components and methods of the PNSQA, including (1) surveys of stream habitat and aquatic biota, (2) discrete water sampling, (3) deployment of passive polar organic chemical integrative samplers for pesticides and pharmaceuticals, and (4) sampling of streambed sediment. At selected study sites, toxicity testing of streambed sediment, continuous water-quality monitoring, and daily pesticide sampling also were conducted and are described.

Oregon, Washington↗
USGS2016

Stock assessment in inland fisheries: a foundation for sustainable use and conservation

Fisheries stock assessments are essential for science-based fisheries management. Inland fisheries pose challenges, but also provide opportunities for biological assessments that differ from those encountered in large marine fisheries for which many of our assessment methods have been developed. These include the number and diversity of fisheries, high levels of ecological and environmental variation, and relative lack of institutional capacity for assessment. In addition, anthropogenic impacts on habitats, widespread presence of non-native species and the frequent use of enhancement and restoration measures such as stocking affect stock dynamics. This paper outlines various stock assessment and data collection approaches that can be adapted to a wide range of different inland fisheries and management challenges. Although this paper identifies challenges in assessment, it focuses on solutions that are practical, scalable and transferrable. A path forward is suggested in which biological assessment generates some of the critical information needed by fisheries managers to make effective decisions that benefit the resource and stakeholders.

Reviews in Fish Biology and Fisheries↗
USGS2000

Responses of physical, chemical, and biological indicators of water quality to a gradient of agricultural land use in the Yakima River Basin, Washington

The condition of 25 stream sites in the Yakima River Basin, Washington, were assessed by the U.S. Geological Survey's National Water-Quality Assessment Program. Multimetric condition indices were developed and used to rank sites on the basis of physical, chemical, and biological characteristics. These indices showed that sites in the Cascades and Eastern Cascades ecoregions were largely unimpaired. In contrast, all but two sites in the Columbia Basin ecoregion were impaired, some severely. Agriculture (nutrients and pesticides) was the primary factor associated with impairment and all impaired sites were characterized by multiple indicators of impairment. All indices of biological condition (fish, invertebrates, and algae) declined as agricultural intensity increased. The response exhibited by invertebrates and algae suggested a threshold response with conditions declining precipitously at relatively low levels of agricultural intensity and little response at moderate to high levels of agricultural intensity. This pattern of response suggests that the success of mitigation will vary depending upon where on the response curve the mitigation is undertaken. Because the form of the community condition response is critical to effective water-quality management, the National Water-Quality Assessment Program is conducting studies to examine the response of biota to gradients of land-use intensity and the relevance of these responses to water-quality management. These land-use gradient pilot studies will be conducted in several urban areas starting in 1999.

Environmental Monitoring and Assessment↗
USGS2023

Genetic erosion in an endangered desert fish during a multidecadal megadrought despite long-term supportive breeding

Human water use combined with a recent megadrought have reduced river and stream flow through the Southwestern United States and led to periodic drying of formerly perennial river segments. Reductions in snowmelt runoff and increased extent of drying collectively threaten short-lived, obligate aquatic species, including the endangered Rio Grande silvery minnow. This species experiences ‘boom-and-bust’ population dynamics where large fluctuations in abundance are expected to lower estimates of effective population size and erode genetic diversity over time. Rates of diversity loss are also affected by additions of hatchery-origin fish used to supplement the wild population. We leveraged demographic and genetic data from wild and hatchery individuals to understand the relationship of genetic diversity and effective population size to abundance over the last two decades. Genetic diversity was low during the early 2000s, but diversity and demographic metrics stabilized after the hatchery program was initiated and environmental conditions improved. Yet, from 2017 onward, allelic diversity declined (Cohen's d = 1.34) and remains low despite hatchery stocking and brief wild population recovery. Across the time series, single-sample estimates of effective population size (N eD ) were positively associated ( r = 0.53) with wild/total abundance, but as the proportion of hatchery-origin spawners increased, N eD was reduced ( r = -0.55). Megadrought limits wild spawner abundance and precludes refreshment of hatchery brood stocks with wild fish, hence we predict a riverine population increasingly dominated by hatchery-origin individuals and accelerated loss of genetic diversity despite supplementation. We recommend an adaptive and accelerated management plan that integrates river flow management and hatchery operations to slow the pace of genetic diversity loss exacerbated by megadrought.

New Mexico↗
USGS1988

Nutritional values of waterfowl foods

wetland habitats throughout their annual cycles. Survival, reproduction, and growth are dependent on the availability of foods that meet nutritional requirements for recurring biological events. These requirements occur among a wide variety of environmental conditions that also influence nutritional demands. Recent work on nesting waterfowl has identified the female’s general nutrient needs for egg laying and incubation. Far less is known about nutritional requirements for molt and other portions of the life cycle, particularly those during the nonbreeding season. Although information on specific requirements for amino acids and micronutrients of wild birds is meager, the available information on waterfowl requirements can be used to develop waterfowl management strategies. For example, nutrient content of foods, nutritional requirements of waterfowl, and the cues waterfowl use in locating and selecting foods are all kinds of information that managers need to encourage use of habitats by feeding waterfowl. Waterfowl nutritional needs during the annual cycle and the nutritional values of natural foods and crops will be discussed below.

Fish and Wildlife Leaflet↗
USGS2020

Lock operations influence upstream passages of invasive and native fishes at a Mississippi River high-head dam

Asian carps continue to expand their range in North America, necessitating efforts to limit the spread and establishment of reproducing populations. Mississippi River Lock and Dam 19 is a high-head dam that represents a population ‘pinch-point’ as passage through the lock chamber is the only means by which fishes can complete upstream movement. As such, this location could be a pivotal control point for minimizing the spread of invasive fishes in the Upper Mississippi River and a possible candidate site for installation of deterrent measures. Our objectives were (1) to study the timing (i.e., weekly and diel) and behavior of fishes in the downstream lock approach, (2) evaluate the relation of presence in the downstream lock approach with environmental factors and lock operation, and (3) identify any upstream or downstream passage events through the lock chamber and the relation between these events and the operation of the lock. Acoustic transmitters were surgically implanted into 262 Asian carps and 216 native fishes to monitor fish activity on a telemetry receiver array deployed around and within the lock for 622 days during 2017–2018. One hundred eighty-six telemetered fish were detected in the downstream lock approach. We documented 14 upstream Asian carp passages and 10 upstream native fish passages; these passages coincided with a specific sequence of large vessel lockages. The results of this study advance our understanding of fish presence and behavior at a Mississippi River mainstem lock and dam and inform the development and testing of deterrent systems at this location or at similar pinch-point lock and dams.

Missouri, Iowa, Illinois↗
USGS2022

Phenological variation in spring migration timing of adult alewife (Alosa pseudoharengus) in coastal Massachusetts

The timing of biological events in plants and animals, such as migration and reproduction, is shifting due to climate change. Anadromous fishes are particularly susceptible to these shifts as they are subject to strong seasonal cycles when transitioning between marine and freshwater habitats to spawn. We used linear models to determine the extent of phenological shifts in adult Alewife Alosa pseudoharengus as they migrated from ocean to freshwater environments during spring to spawn at 12 sites along the northeastern USA. We also evaluated broadscale oceanic and atmospheric drivers that trigger their movements from offshore to inland habitats, including sea surface temperature, North Atlantic Oscillation index, and Gulf Stream index. Run timing metrics of initiation, median (an indicator of peak run timing), end, and duration were found to vary among sites. Although most sites showed negligible shifts towards earlier timing, statistically significant changes were detected in three systems. Overall, winter sea surface temperature, spring and fall transition dates, and annual run size were the strongest predictors of run initiation and median dates, while a combination of within-season and seasonal-lag effects influenced run end and duration timing. Disparate results observed across the 12 spawning runs suggest that regional environmental processes were not consistent drivers of phenology and local environmental and ecological conditions may be more important. Additional years of data to extend time series and monitoring of Alewife timing and movements in nearshore habitats may provide important information about staging behaviors just before adults transition between ocean and freshwater habitats.

Massachusetts↗
USGS2022

Understanding the Avian-Impact Offset Method—A tutorial

Biodiversity offsetting, or compensatory mitigation, is increasingly being used in temperate grassland and wetland ecosystems to compensate for unavoidable environmental damage from anthropogenic disturbances such as energy development and road construction. Energy-extraction and -generation facilities continue to proliferate across the natural landscapes of the United States, yet mitigation tools to ameliorate the negative behavioral effects on wildlife from these types of facilities are rarely implemented. Scientists from the U.S. Geological Survey conducted a 10-year before-after-control-impact (commonly referred to as BACI) study that evaluated the displacement effects of wind facilities on breeding grassland birds. The study determined behavioral avoidance for 7 of 9 species. This research is notable because of its design, geographical scope, and duration, which allowed for the determination of immediate, short-term effects; delayed or sustained effects; and discrete distances at which effects occurred. In addition, the U.S. Fish and Wildlife Service and Ducks Unlimited conducted a 3-year concurrent-year paired-reference study to determine behavioral avoidance for five species of dabbling ducks. By quantifying displacement rate from these two studies, U.S. Geological Survey and U.S. Fish and Wildlife Service scientists developed the Avian-Impact Offset Method (AIOM) to quantify and compensate for loss in value of breeding habitat. The AIOM converts the biological value (that is, number of bird pairs) lost by way of avoidance and estimates the site-specific number of hectares of grasslands and number of wetlands needed to compensate for displaced pairs of grassland birds and waterfowl. By converting biological value to traditional units of measure in which land is described and purchased or sold, the AIOM lends itself readily to the delivery of offsetting measures such as easement protections and restoration projects. The AIOM tool is applicable to wind, solar, oil, gas, and transportation infrastructure. This tutorial was designed to increase awareness of the AIOM and to promote its proper application. The tutorial is divided into four sections, each of which explains a discrete topic concerning aspects of behavioral displacement. The first section provides geographical and biological context, and the second section describes the field and statistical methods and results. The third section provides step-by-step instructions for applying the AIOM to several scenarios involving grassland birds or waterfowl at wind or oil facilities. The fourth section describes decision-support tools created to implement the AIOM. The appendices provide the actual field protocols constituting the methods for the research, provide detailed results by species and wind facility for that research, and provide detailed instructions for downloading and applying the decision-support tools.

Open-File Report↗
USGS2012

Pacific salmonines in the Great Lakes Basin

Pacific salmon (genus Oncorhynchus) are a valuable resource, both within their native range in the North Pacific rim and in the Great Lakes basin. Understanding their value from a biological and economic perspective in the Great Lakes, however, requires an understanding of changes in the ecosystem and of management actions that have been taken to promote system stability, integrity, and sustainable fisheries. Pacific salmonine introductions to the Great Lakes are comprised mainly of Chinook salmon, coho salmon, and steelhead and have accounted for 421, 177, and 247 million fish, respectively, stocked during 1966-2007. Stocking of Pacific salmonines has been effective in substantially reducing exotic prey fish abundances in several of the Great Lakes (e.g., lakes Michigan, Huron, and Ontario). The goal of our evaluation was to highlight differences in management strategies and perspectives across the basin, and to evaluate policies for Pacific salmonine management in the Great Lakes. Currently, a potential conflict exists between Pacific salmonine management and native fish rehabilitation goals because of the desire to sustain recreational fisheries and to develop self-sustaining populations of stocked Pacific salmonines in the Great Lakes. We provide evidence that suggests Pacific salmonines have not only become naturalized to the food webs of the Great Lakes, but that their populations (specifically Chinook salmon) may be fluctuating in concert with specific prey (i.e., alewives) whose populations are changing relative to environmental conditions and ecosystem disturbances. Remaining questions, however, are whether or not “natural” fluctuations in predator and prey provide enough “stability” in the Great Lakes food webs, and even more importantly, would a choice by managers to attempt to reduce the severity of predator-prey oscillations be antagonistic to native fish restoration efforts. We argue that, on each of the Great Lakes, managers are pursuing appropriate goals, managing the aquatic resources of the lakes for the greatest public good, given the variability in conditions and likelihood for success specific to each lake.

Book chapter↗
USGS1989

Assessing the relationship between Section 404 and wetland losses: a feasibility study

The primary objective of the Clean Water Act of 1977 (33 U.S.C. 1251) is to restore and maintain the physical, chemical, and biological integrity of the Nation's waters. Section 404 of the Act regulates the discharge of dredged or fill materials into wetlands and represents the primary Federal authority for regulation of wetland alterations. Since its inception, the Section 404 program has been controversial in regard to the extent to which it was intended to provide wetlands regulation. Section 404 requires those who wish to discharge dredged or fill material into waters of the United States, which include many wetlands, to first obtain a Federal permit. The Environmental Protection Agency (EPA) has overall responsibility for administration of the Section 404 program and promulgates guidelines that must be followed in issuing permits. In addition, EPA has the final authority to prohibit specific discharges if the environmental impacts are unacceptable. The U.S. Army Corps of Engineers (Corps) issues Section 404 permits, which can be of two types. Individual Permits are issued following case-by-case reviews of proposed discharges. General Permits, which can be either nationwide or regional in scope, are authorized by the Corps for categories of activities that are similar in nature and that have only minimal individual and cumulative adverse environmental impacts. EPA, the National Marine Fisheries Service (NMFS), the Fish and Wildlife Service (Service), and State natural resource agencies review and comment on permit applications and offer recommendations on appropriate mitigation measures. Although comments from the Service and other natural resource agencies are advisory in nature (EPA's veto authority excepted), they can serve as the basis for modifying, conditioning, or denying a Section 404 permit. In 1986, in a survey conducted by the National Ecology Research Center, Service personnel indicated interest in additional information concerning both wetland trends and the impacts of activities authorized by the Corps under Section 404 (Roelle 1986). Although there is some information concerning wetland losses for certain geographic areas and for the Nation as a whole (Frayer et al. 1983; Tiner 1984), there appears to be little information on how these losses relate to the Section 404 permitting process. The primary objective of this study was to determine the feasibility of estimating wetland losses in relationship to Individual and General Permits issued under Section 404. A secondary objective was to assemble data on acceptance and implementation of specific mitigation recommendations offered by the Service and other natural resource agencies in connection with development activities on wetlands examined. At present, 26 categories of Nationwide permits have been authorized by the Corps. Nationwide permit 26 was of particular interest in this study because it specifically authorizes discharges into wetlands under certain circumstances (see Figure 1 and related text for a more complete discussion of circumstances under which Nationwide Permit 26 is applicable). All subsequent references to Nationwide or General permits pertain to Nationwide Permit 26.

Report↗
USGS2025

Occurrence and tissue distribution of per- and polyfluoroalkyl substances (PFAS) in fishes from waterbodies with point and non-point sources in Massachusetts, USA

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants with known bioaccumulative and toxic effects in aquatic ecosystems. This study assessed site-specific differences in PFAS contamination in fish from Ashumet Pond, Sudbury River, and Great Herring Pond (reference site) in Massachusetts. Fish from Ashumet Pond exhibited the highest PFAS concentrations, particularly perfluorooctane sulfonate (PFOS), which exceeded levels in plasma almost 650 times those at the reference site. Principal component analysis identified distinct PFAS profiles at each site, reflecting localized contamination sources. Temporal analysis at Ashumet Pond revealed a substantial increase in plasma PFOS and perfluorodecanoic acid (PFDA) from 2020 to 2022. Tissue distribution analyses showed the highest PFAS concentrations in plasma, followed by liver and muscle, consistent with PFAS binding affinity for blood proteins. Species-specific differences in PFAS bioaccumulation were observed, with largemouth bass ( Micropterus nigricans ) exhibiting higher body burdens than banded killifish ( Diaphanus fundulus ), likely due to trophic position and dietary exposure. Histopathological assessments and gene transcript analyses revealed associations between PFAS exposure and inflammatory responses, oxidative stress, endocrine disruption, and immune-related pathways, with the most pronounced molecular effects observed at the downstream site of the Sudbury River. This study underscores the importance of understanding site-specific contamination sources, exposure pathways, and biological effects of PFAS in fish. These findings would benefit from additional research on sediment contamination, temporal analyses at each site, trophic transfer, and transcriptomic analyses across multiple organs to further elucidate PFAS toxicity mechanisms and guide remediation efforts.

Massachusetts↗
USGS2024

Fish size structures in lakes of the Lower Mississippi River floodplain

The Lower Mississippi River has a floodplain that includes >1350 perennial lakes carved by shifts in river courses and other hydro-fluvial processes over eons. Notwithstanding their similar provenances, these waterbodies exhibit an immense variety of morphologies and successional stages that illustrate their natural trajectory from aquatic to forested wetlands. A result of this geographical, morphological and temporal diversity is dynamic and varied fish communities. We examined how size structures of fish communities in these floodplain lakes were associated with key in-lake and off-lake environmental drivers. Fish lengths were collected with standardised procedures in a sample of 30 of these lakes to construct a lake-by-length group matrix. Likewise, in-lake and off-lake environmental descriptors were collected to construct a lake-by-covariate matrix. Distance-based linear models were used to assess associations between fish size structure and environmental descriptors. Smaller fish were typically associated with increasing levels of turbidity, chlorophyll- a , phycocyanin and surrounding agriculture. Shallow, hypereutrophic floodplain lakes associated with agricultural landscapes and reduced connectivity experience harsh physicochemical environments. These conditions appeared to hinder the formation of sustained fish communities but may confer a survival advantage to juveniles or small short-lived species. Conversely, larger fish were associated with increasing lake depth, water clarity, connectivity, and extent of surrounding forests-wetlands. Enhanced stability and size structure were observed in communities residing in deeper and clearer lakes, suggesting that these conditions facilitated the development of longer-lived species spanning multiple age groups. The enhanced connectivity that facilitated this increased stability also permitted the presence of larger itinerant species. Size-structure assessments can serve as a valuable ecological and biodiversity indicator in floodplain lakes. Size-structure assessments could supplement and, depending on objectives, even supplant conventional taxonomic analyses, and enhance surveillance of this vast and important natural resource.

Arkansas, Louisiana, Mississippi, Missouri, Tennes↗
USGS2020

Diversity of diatoms, benthic macroinvertebrates, and fish varies in response to different environmental correlates in Arctic rivers across North America

Climate change poses a significant threat to Arctic freshwater biodiversity, but impacts depend upon the strength of organism response to climate‐related drivers. Currently, there is insufficient knowledge about Arctic freshwater biodiversity patterns to guide assessment, prediction, and management of biodiversity change. As part of the Circumpolar Biodiversity Monitoring Program's first freshwater assessment, we evaluated diversity of diatoms, benthic macroinvertebrates, and fish in North American Arctic rivers. Alpha diversity was assessed in relation to temperature, water chemistry, bedrock geology, and glaciation history to identify important environmental correlates. Biotic composition was compared among groups to evaluate response to environmental gradients. Macroinvertebrate α‐diversity declined strongly with increasing latitude from 48°N to 82°N, whereas diatom and fish diversity peaked around 70°N without a clear latitudinal decline. Macroinvertebrate diversity was significantly positively related to air temperature. Diatom diversity was related to bedrock geology and temperature, whereas fish diversity was related to glaciation history. Fish and macroinvertebrate assemblages differed between sites in western Canada, where invertebrate composition was more variable, and Alaska, where fish composition was more variable. In sites with both diatom and macroinvertebrate data, diatom composition was distinct in Alaska, where richness was highest in former glacial refugia. Macroinvertebrate composition was distinct in lowest‐latitude eastern and high‐latitude western Canadian sites where temperature was highest. Temperature, precipitation, geology, calcium, and substrate size were important environmental correlates for diatoms and macroinvertebrates, although the relative importance of each correlate differed. Diatom taxa were most strongly associated with water chemistry, whereas benthic invertebrate composition related most strongly to precipitation and temperature. This large‐scale study provides the most substantial integration and analysis of river diatom, macroinvertebrate, and fish data from the North American Arctic to date. Findings suggest that macroinvertebrates will show the strongest response to climate‐related shifts in temperature, whereas diatoms and fish are more likely to respond to climate‐induced shifts in nutrients and hydraulic connectivity. However, significant gaps in data coverage limited our ability to reliably evaluate spatial patterns and detect change. These gaps could be reduced by improving collaborative efforts between the U.S.A. and Canada to harmonise future monitoring.

Arctic↗
USGS2007

Chinook salmon use of spawning patches: Relative roles of habitat quality, size, and connectivity

Declines in many native fish populations have led to reassessments of management goals and shifted priorities from consumptive uses to species preservation. As management has shifted, relevant environmental characteristics have evolved from traditional metrics that described local habitat quality to characterizations of habitat size and connectivity. Despite the implications this shift has for how habitats may be prioritized for conservation, it has been rare to assess the relative importance of these habitat components. We used an information-theoretic approach to select the best models from sets of logistic regressions that linked habitat quality, size, and connectivity to the occurrence of chinook salmon (Oncorhynchus tshawytscha) nests. Spawning distributions were censused annually from 1995 to 2004, and data were complemented with field measurements that described habitat quality in 43 suitable spawning patches across a stream network that drained 1150 km 2 in central Idaho. Results indicated that the most plausible models were dominated by measures of habitat size and connectivity, whereas habitat quality was of minor importance. Connectivity was the strongest predictor of nest occurrence, but connectivity interacted with habitat size, which became relatively more important when populations were reduced. Comparison of observed nest distributions to null model predictions confirmed that the habitat size association was driven by a biological mechanism when populations were small, but this association may have been an area-related sampling artifact at higher abundances. The implications for habitat management are that the size and connectivity of existing habitat networks should be maintained whenever possible. In situations where habitat restoration is occurring, expansion of existing areas or creation of new habitats in key areas that increase connectivity may be beneficial. Information about habitat size and connectivity also could be used to strategically prioritize areas for improvement of local habitat quality, with areas not meeting minimum thresholds being deemed inappropriate for pursuit of restoration activities. ?? 2007 by the Ecological Society of America.

Ecological Applications↗
USGS2017

A regional assessment of chemicals of concern in surface waters of four Midwestern United States national parks

Anthropogenic chemicals and their potential for adverse biological effects raise concern for aquatic ecosystem health in protected areas. During 2013–15, surface waters of four Midwestern United States national parks were sampled and analyzed for wastewater indicators, pharmaceuticals, personal care products, and pesticides. More chemicals and higher concentrations were detected at the two parks with greater urban influences (Mississippi National River and Recreation Area and Indiana Dunes National Lakeshore) than at the two more remote parks (Apostle Islands National Lakeshore and Isle Royale National Park). Atrazine (10–15 ng/L) and N,N-diethyl-meta-toluamide (16–120 ng/L) were the only chemicals detected in inland lakes of a remote island national park (Isle Royale National Park). Bisphenol A and organophosphate flame retardants were commonly detected at the other sampled parks. Gabapentin and simazine had the highest observed concentrations (> 1000 ng/L) in three and two samples, respectively. At the two parks with urban influences, metolachlor and simazine concentrations were similar to those reported for other major urban rivers in the United States. Environmental concentrations of detected chemicals were often orders of magnitude less than standards or reference values with three exceptions: (1) hydrochlorothiazide exceeded a human health-based screening value in seven samples, (2) estrone exceeded a predicted critical environmental concentration for fish pharmacological effects in one sample, and (3) simazine was approaching the 4000 ng/L Maximum Contaminant Level in one sample even though this concentration is not expected to reflect peak pesticide use. Although few environmental concentrations were approaching or exceeded standards or reference values, concentrations were often in ranges reported to elicit effects in aquatic biota. Data from this study will assist in establishing a baseline for chemicals of concern in Midwestern national parks and highlight the need to better understand the sources, pathways, and potential adverse effects to aquatic systems in national parks.

Indiana, Michigan, Minnesota, Wisconsin↗