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USGS2019

Water-quality, bed-sediment, and biological data (October 2016 through September 2017) and statistical summaries of data for streams in the Clark Fork Basin, Montana

Water, bed sediment, and biota were sampled in selected streams from Butte to near Missoula, Montana, as part of a monitoring program in the Clark Fork Basin of western Montana. The sampling program was led by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Clark Fork Basin and emphasize trace elements associated with historic mining and smelting activities. Sampling sites were on the Clark Fork and selected tributaries. Water samples were collected periodically at 20 sites from October 2016 through September 2017. Bed-sediment and biota samples were collected once at 13 sites during August 2017. This report presents the analytical results and quality-assurance data for water-quality, bed-sediment, and biota samples collected at sites from October 2016 through September 2017. Water-quality data include concentrations of selected major ions, dissolved organic carbon, turbidity, nitrogen (nitrate plus nitrite), trace elements, and suspended sediment. Seasonal daily values of turbidity were determined at four sites. Bed-sediment data include trace-element concentrations in the fine-grained (less than 0.063 millimeter) fraction. Biological data include trace-element concentrations in whole-body tissue of aquatic benthic insects. Statistical summaries of water-quality, bed-sediment, and biological data for sites in the Clark Fork Basin are provided for the period of record.

Montana↗

USGS1994

Water-quality, bed-sediment, and biological data (October 1992 through September 1993) and statistical summaries of water-quality data (March 1985 through September 1993) for streams in the upper Clark Fork basin, Montana

Water, bed sediment, and biota were sampled in streams from Butte to below Missoula as part of a program to characterize aquatic resources in the upper Clark Fork basin of western Montana. Water-quality data were obtained periodically at 16 stations during October 1992 through September 1993 (water year 1993); daily suspended-sediment data were obtained at six of these stations. Bed-sediment and biological data were obtained at 11 stations in August 1993. Sampling stations were located on the Clark Fork and major tributaries. The primary constituents analyzed were trace elements associated with mine tailings from historic mining and smelting activities. Water-quality data include concentra- tions of major ions, trace elements, and suspended sediment in samples collected periodically during water year 1993. A statistical summary of water- quality data is provided for the period of record at each station since 1985. Daily values of streamflow, suspended-sediment concentration, and suspended-sediment discharge are given for six stations. Bed-sediment data include trace- element concentrations in the fine and bulk fractions. Biological data include trace-element concentrations in whole-body tissue of aquatic benthic insects. Quality-assurance data are reported for analytical results of water, bed sediment, and biota.

Open-File Report↗

USGS1995

Water-quality, bed-sediment, and biological data (October 1993 through September 1994) and statistical summaries of data for streams in the Upper Clark Fork basin, Montana

Water, bed sediment, and biota were sampled in streams from Butte to below Missoula as part of a program to characterize aquatic resources in the upper Clark Fork basin of western Montana. Water- quality data were obtained periodically at 16 stations during October 1993 through September 1994 (water year 1994); daily suspended-sediment data were obtained at six of these stations. Bed-sediment and biological data were obtained at 11 stations in August 1994. Sampling stations were located on the Clark Fork and major tributaries. The primary constituents analyzed were trace elements associated with mine tailings from historical mining and smelting activities. Water-quality data include concentrations of major ions, trace elements, and suspended sediment in samples collected periodically during water year 1994. Daily values of streamflow, suspended-sediment concentration, and suspended- sediment discharge are given for six stations. Bed- sediment data include trace-element concentrations in the fine and bulk fractions. Biological data include trace-element concentrations in whole-body tissue of aquatic benthic insects. Quality-assurance data are reported for analytical results of water, bed sediment, and biota. Statistical summaries of bed sediment, and biological data are provided for the period of record at each station since 1985.

Open-File Report↗

USGS1996

Water-quality, bed-sediment, and biological data (October 1994 through September 1995) and statistical summaries of data for streams in the upper Clark Fork basin, Montana

Water, bed sediment, and biota were sampled in streams from Butte to below Missoula as part of a program to characterize aquatic resources in the upper Clark Fork basin of western Montana. Sampling stations were located on the Clark Fork and major tributaries. Water-quality data were obtained periodically at 16 stations during October 1994 through September 1995 (water year 1995). Data for twelve bed-sediment and eleven biological stations were obtained in August 1995. The primary constituents analyzed were trace elements associated with mine tailings from historical mining and smelting activities. Water-quality data include concentrations of major ions, trace element, and suspended sediment in stream samples collected periodically during water year 1995. Daily values of streamflow, suspended- sediment concentrations in the fine-grained and bulk fractions. Biological data include trace- element concentrations in whole-body tissue of aquatic benthic insects. Quality-assurance data are reported for analytical results of water, bed sediment, and biota. Statistical summaries of water-quality, bed-sediment, and biological data are provided for the period of record at each station since 1985.

Montana↗

USGS2025

Scalable environmental DNA methods reveal strong associations between landscape-scale forest habitat and insect richness

While aquatic environmental DNA (eDNA) methods have reached relative maturity, terrestrial eDNA methods are nascent and have yet to reach widespread use. Field-ready applications require eDNA survey methods where samples are easy to collect by inexperienced practitioners, easy to transport between the field and lab, and easy to process thereafter. Here, we demonstrate methods that satisfy these requirements and show strong potential for characterizing diverse terrestrial eDNA samples collected from flower and leaf surfaces. We used novel methods to collect and process 236 flower eDNA samples and 21 leaf surface eDNA samples, obtaining 2,228 Arthropoda eDNA detections spanning 175 families using amplicon sequencing of two genetic markers. Detected taxa were diverse and included numerous groups of conservation concern, such as bees (Hymenoptera; Anthophila, 32 genera spanning 5 families) and Lepidoptera (209 genera from 21 families). Data reveal strong associations between insect community richness and remotely sensed measures of forest habitat, providing a quantitative perspective of relevance to insect conservation. It is increasingly clear that a variety of organisms readily disperse eDNA throughout the environment, supporting the notion that eDNA will be a powerful tool for characterizing species distributions and monitoring at-risk species. However, we conclude that researchers seeking to characterize fine-scale habitat associations or plant-pollinator interactions using eDNA will need to carefully design studies with appropriate field controls, such as the leaf surface eDNA samples collected here.

BioRxiv↗

USGS2019

Reverberating effects of resource exchanges in stream–riparian food webs

Fluxes of materials or organisms across ecological boundaries, often termed “resource subsidies,” directly affect recipient food webs. Few studies have addressed how such direct responses in one ecosystem may, in turn, influence the fluxes of materials or organisms to other habitats or the potential for feedback relationships to occur among ecosystems. As part of a large-scale, multi-year experiment, we evaluated the hypothesis that the input of a marine-derived subsidy results in a complex array of resource exchanges (i.e., inputs, outputs, feedbacks) between stream and riparian ecosystems as responses disperse across ecological boundaries. Moreover, we evaluated how the physical properties of resource subsidies mediated complex responses by contrasting carcasses with a pelletized salmon treatment. We found that salmon carcasses altered stream–riparian food webs by directly subsidizing multiple aquatic and terrestrial organisms (e.g., benthic insect larvae, fishes, and terrestrial flies). Such responses further influenced food webs along indirect pathways, some of which spanned land and water (e.g., subsidized fishes reduced aquatic insect emergence, with consequences for spiders and bats). Subsidy-mediated feedbacks manifested when carcasses were removed to riparian habitats where they were colonized by carrion flies, some of which fell into the stream and acted as another prey subsidy for fishes. As the effects of salmon subsidies propagated through the stream–riparian food web, the sign of consumer responses was not always positive and appeared to be determined by the outcome of trophic interactions, such that localized trophic interactions within one ecosystem mediated the export of organisms to others.

Idaho↗

USGS2014

An ecological response model for the Cache la Poudre River through Fort Collins

The Poudre River Ecological Response Model (ERM) is a collaborative effort initiated by the City of Fort Collins and a team of nine river scientists to provide the City with a tool to improve its understanding of the past, present, and likely future conditions of the Cache la Poudre River ecosystem. The overall ecosystem condition is described through the measurement of key ecological indicators such as shape and character of the stream channel and banks, streamside plant communities and floodplain wetlands, aquatic vegetation and insects, and fishes, both coolwater trout and warmwater native species. The 13- mile-long study area of the Poudre River flows through Fort Collins, Colorado, and is located in an ecological transition zone between the upstream, cold-water, steep-gradient system in the Front Range of the Southern Rocky Mountains and the downstream, warm-water, low-gradient reach in the Colorado high plains. The City wanted to better understand the ecological response of the Poudre River ecosystem to potential changes in stream flow and other physical parameters through the conceptual framework of a multivariable integrated model. This goal was met through the use of a probabilistic model based on Bayesian concepts. This construct allowed the integration of a wide range of data and expert opinion (as informed by local data) to predict potential changes to ecosystem conditions under various flow scenarios. Nine flow scenarios representing past, present, and possible future hydrology were developed as the primary model input. Both reach-scale drivers such as stream channel conditions and pollutant loads, as well as ecological conditions, including species composition, interactions, and habitat requirements influenced model-predicted ecosystem outcomes. Model output consisted of probability distributions for eight ecological indicators collectively representing the physical setting, aquatic life, and riparian habitats of the river ecosystem. We are confident in model predictions related to probable trends, relative magnitude of changes and potential ecosystem responses to changing flow conditions, though data availability and the process of converting diverse data types into a common unit (probabilities) limit precision of individual results. Key findings suggest that: The present ecological function of the Poudre River is altered as a result of more than 150 years of human influences that include highly managed flows, urbanization, gravel mining, channelization and urban and industrial encroachment in the floodplain, underscoring the vulnerable and complex character of the Poudre River; A continuation of today’s flow management will lead to ongoing changes in ecosystem condition, and additional water depletions will compromise ecological conditions; High flows play an essential role in maintaining and improving the aquatic and riparian condition of the river; Adequate flows in base-flow periods are critical to desirable water quality, and thriving fish and insect populations; Improvement of native aquatic life is possible if issues related to channel modifications, siltation, invasive species, and base and high flow conditions are managed properly; The present confined river channel and modified flows has reduced the potential for a keystone and iconic species, plains cottonwood, to be self-sustaining in the study area; The streamside corridor retains the potential to support a functioning riparian forest that provides important ecological services if periodic floodplain inundation occurs. Environmental flows that combine stable and adequate flows in base-flow periods with occasional rejuvenating high flows that meet target levels defined in this study are likely improve all biological indicators across the system. ERM test scenarios that include both stable base flows and rejuvenating high flows indicate that substantial improvements in the river ecosystem can be achieved with improved management of flow volumes similar to those observed in the river during the last half century of intensive water development. These results underscore the possibility of improving the river ecosystem through active management while still maintaining the Poudre’s diverse economic benefits and role as a working river. The ERM was designed to represent the multi-dimensional ecological character of the contemporary urban Poudre River. It provides a scientific foundation that can serve as a decision support tool and foster a more informed community discussion about the future of the river as it provides a better understanding of the likely response of the Poudre River ecosystem to environmental flow management and other stewardship activities. In particular, model results can assist managers in developing specific management actions to achieve desirable goals for key indicators of river health.

Colorado↗

USGS2021

Hydropeaking intensity and dam proximity limit aquatic invertebrate diversity in the Colorado River Basin

River biodiversity is threatened globally by hydropower dams, and there is a need to understand how dam management favors certain species while filtering out others. We examined aquatic invertebrate communities within the tailwaters 0–24 km downstream of seven large hydropower dams in the Colorado River Basin of the western United States. We quantified aquatic invertebrate dominance, richness, abundance, and biomass at multiple locations within individual tailwaters and across the basin and identified biological community responses associated with dam operations and distance from dam. We found that each tailwater was dominated by 3–7 invertebrate taxa, accounting for 95% of total abundance. Half of these dominant taxa were non-insect, non-flying species and thus were unavailable to terrestrial consumers. Consistent with previous studies, aquatic insects and sensitive taxa were negatively associated with hydropeaking intensity (magnitude of daily flow fluctuations associated with hydropower generation), which limits the composition and potentially the quality of the invertebrate food base. While total invertebrate abundance and biomass did not change with increasing distance downstream from dams, insect and sensitive taxa richness, abundance, and biomass all increased, suggesting that impacts of hydropeaking are most acute immediately downstream of dams. Our results demonstrate that tailwaters experiencing hydropeaking support high abundances of aquatic invertebrate, but the diversity of these communities is low.

Arizona, California, Colorado, Nevada, New Mexico,↗

USGS2021

Clothianidin decomposition in Missouri wetland soils

Neonicotinoid pesticides can persist in soils for extended time periods; however, they also have a high potential to contaminate ground and surface waters. Studies have reported negative effects associated with neonicotinoids and nontarget taxa, including aquatic invertebrates, pollinating insect species, and insectivorous birds. This study evaluated factors associated with clothianidin (CTN) degradation and sorption in Missouri wetland soils to assess the potential for wetland soils to mitigate potential environmental risks associated with neonicotinoids. Solid-to-solution partition coefficients ( K d ) for CTN sorption to eight wetland soils were determined via single-point sorption experiments, and sorption isotherm experiments were conducted using the two most contrasting soils. Clothianidin degradation was determined under oxic and anoxic conditions over 60 d. Degradation data were fit to zero- and first-order kinetic decay models to determine CTN half-life ( t 0.5 ). Sorption results indicated CTN sorption to wetland soil was relatively weak (average K d , 3.58 L kg –1 ); thus, CTN has the potential to be mobile and bioavailable within wetland soils. However, incubation results showed anoxic conditions significantly increased CTN degradation rates in wetland soils (anoxic average t 0.5 , 27.2 d; oxic average t 0.5 , 149.1 d). A significant negative correlation was observed between anoxic half-life values and soil organic C content ( r 2 = .782; p = .046). Greater CTN degradation rates in wetland soils under anoxic conditions suggest that managing wetlands to facilitate anoxic conditions could mitigate CTN presence in the environment and reduce exposure to nontarget organisms.

Missouri↗

USGS2011

Growth characteristics and otolith analysis on age-0 American shad

Otolith microstructure analysis provides useful information on the growth history of fish (Campana and Jones 1992, Bang and Gronkjaer 2005). Microstructure analysis can be used to construct the size-at-age growth trajectory of fish, determine daily growth rates, and estimate hatch date and other ecologically important life history events (Campana and Jones 1992, Tonkin et al. 2008). This kind of information can be incorporated into bioenergetics modeling, providing necessary data for estimating prey consumption, and guiding the development of empirically-based modeling scenarios for hypothesis testing. For example, age-0 American shad co-occur with emigrating juvenile fall Chinook salmon originating from Hanford Reach and the Snake River in the lower Columbia River reservoirs during the summer and early fall. The diet of age-0 American shad appears to overlap with that of juvenile fall Chinook salmon (Chapter 1, this reoprt), but juvenile fall Chinook salmon are also known to feed on age-0 American shad in the reservoirs (USGS unpublished data). Abundant, energy-dense age-0 American shad may provide juvenile fall Chinook salmon opportunities for rapid growth during the time period when large number of age-0 American shad are available. Otolith analysis of hatch dates and the growth curve of age-0 American shad could be used to identify when eggs, larvae, and juveniles of specific size classes are temporally available as food for fall Chinook salmon in the lower Columbia River reservoirs. This kind of temporally and spatially explicit life history information is important to include in bioenergetics modeling scenarios. Quantitive estimates of prey consumption could be used with spatially-explicit estimates of prey abundance to construct a quantitative assessment of the age-0 American shad impact on a reservoir food web. Analysis of the age-0 American shad growth trajectory or individual growth records may show evidence of differential growth rates over time that may be linked to environmental conditions such as water temperature (Leach and Houde 1999, Meekan et al. 2003), size-selective mortality (Folkvord et al. 1997), developmental changes in metabolic rate (Bang and Gronkjaer 2005, Bochdanksy et al. 2005), feeding ability (Schmitt and Holbrook 1984, Luecke 1986, Johnson and Dropkin 1995, Johnson and Dropkin 1996), and intra- and inter-specific competition (Crecco and Savoy 1987, Marchand and Boisclair 1998, Gadomski and Wagner 2009). For example, environmental conditions associated with John Day reservoir may eliminate or reduce the availability of many aquatic and terrestrial insect prey types (Rondorf et al. 1990). Many juvenile fishes, including age-0 American shad and juvenile fall Chinook salmon may be foraging on limited insect prey in John Day Reservoir (Gadomski and Wagner 2009). Because larger insect prey has higher energy densities than most zooplankton prey, and insect availability may be limited in John Day reservoir, the growth of American shad may be constrained once fish grow to a size where they could exploit larger, more energy-dense insect prey (Mayer and Wahl 1997). Similarly, as age-0 American shad grow, they are able to forage on larger zooplankton with higher energy densities than smaller individuals of the same species, or other smaller-bodied zooplankton species (Schael et al. 1991, Mayer and Wahl 1997). Intra- and inter-specific demand for larger-bodied and higher energy zooplankton prey may reduce the availability of these prey items (Tabor et al. 1996). Constrained growth increments on the otolith microstructure of juvenile American shad or other planktivorous fish could help identify important interactions between fishes that may be linked to the year class strength of age-0 American shad and prey partitioning in John Day reservoir. The objective of this study was to determine time of hatch and size-at-age of age-0 American shad in lower Columbia River reservoirs for use with the American shad and fall Chinook salmon bioenergetic models. Size-at-age data on age-0 American shad can be used to generate quantitative estimates of prey consumption with the American shad bioenergetics model. Otolith microstructure analysis was used to provide reference points on the temporal availability of early life stages and sizes of American shad in the reservoir (Limburg 1996a,b, Limburg et al. 1999). Additional analyses on the age-0 American shad growth trajectory in John Day reservoir may reveal differential growth patterns during the early life history of these fish that are linked to developmental differences between individual fish, transient environmental conditions, or food web constraints (Limburg 1996a).

Idaho, Montana, Oregon, Washington, Wyoming↗

USGS2007

Is there a risk associated with the insect repellent DEET (N,N-diethyl-m-toluamide) commonly found in aquatic environments?

DEET ( N , N -diethyl- m -toluamide) is the active ingredient of most commercial insect repellents. This compound has commonly been detected in aquatic water samples from around the world indicating that DEET is both mobile and persistent, despite earlier assumptions that DEET was unlikely to enter aquatic ecosystems. DEET's registration category does not require an ecological risk assessment, thus information on the ecological toxicity of DEET is sparse. This paper reviews the presence of DEET in aqueous samples from around the world (e.g. drinking water, streams, open seawater, groundwater and treated effluent) with reported DEET concentrations ranging from 40–3000 ng L − 1 . In addition, new DEET data collected from 36 sites in coastal waterways from eastern Australia (detections ranging from 8 to 1500 ng L − 1 ) are examined. A summary of new and existing toxicity data are discussed with an emphasis on preparing a preliminary risk assessment for DEET in the aquatic environment. Collated information on DEET in the aquatic environment suggests risk to aquatic biota at observed environmental concentrations is minimal. However, the information available was not sufficient to conduct a full risk assessment due to data deficiencies in source characterisation, transport mechanisms, fate, and ecotoxicity studies. These risks warrant further investigation due to the high frequency that this organic contaminant is detected in aquatic environments around the world.

Science of the Total Environment↗

USGS2017

Metamorphosis affects metal concentrations and isotopic signatures in a mayfly ( Baetis tricaudatus ): Implications for the aquatic-terrestrial transfer of metals

Insect metamorphosis often results in substantial chemical changes that can alter contaminant concentrations and fractionate isotopes. We exposed larval mayflies ( Baetis tricaudatus ) and their food (periphyton) to an aqueous zinc gradient (3-340 µg Zn/l) and measured zinc concentrations at different stages of metamorphosis: larval, subimago, and imago. We also measured changes in stable isotopes (δ 15 N and δ 13 C) in unexposed mayflies. Larval zinc concentrations were positively related to aqueous zinc, increasing 9-fold across the exposure gradient. Adult zinc concentrations were also positively related to aqueous zinc, but were 7-fold lower than larvae. This relationship varied according to adult substage and sex. Tissue concentrations in female imagoes were not related to exposure concentrations, but the converse was true for all other stage-by-sex combinations. Metamorphosis also increased δ 15 N by ~0.8‰, but not δ 13 C. Thus, the main effects of metamorphosis on insect chemistry were large declines in zinc concentrations coupled with increased δ 15 N signatures. For zinc, this change was largely consistent across the aqueous exposure gradient. However, differences among sexes and stages suggest that caution is warranted when using nitrogen isotopes or metal concentrations measured in one insect stage (e.g. larvae) to assess risk to wildlife that feed on subsequent life stages (e.g. adults).

Environmental Science & Technology↗

USGS2012

Water quality and the composition of fish and macroinvertebrate communities in the Devils and Pecos Rivers within and upstream from the Amistad National Recreation Area, Texas, 2005-7

To gain a better understanding of the water quality and status of fish and macroinvertebrate communities, the U.S. Geological Survey, in cooperation with the National Park Service and Amistad National Recreation Area, completed a reconnaissance-level survey of the water quality and fish and macroinvertebrate communities in the Devils and Pecos Rivers in and upstream from the Amistad National Recreation Area in southwest Texas during 2005–7. Water-quality conditions during the spring and summer months of 2005 in the Devils and Pecos Rivers were assessed at locations just upstream from the Amistad National Recreation Area, and the composition of fish and macroinvertebrate communities were assessed during 2006 and 2007 in and upstream from the Amistad National Recreation Area and Amistad Reservoir. Water-quality samples were collected at one site on both the Devils and Pecos Rivers. Fish and macroinvertebrates were collected at the water-quality sampling site on each river and at three additional sites on each river. The water-quality constituents of primary concern were total dissolved solids, chloride, sulfate, ammonia plus organic nitrogen, nitrate plus nitrite, orthophosphate, phosphorus, selenium, and selected pesticides. During the spring and summer of 2005, the concentrations of total dissolved solids ranged from 208 to 232 milligrams per liter (mg/L) in samples from the Devils River compared to 1,460 to 2,390 mg/L in samples from the Pecos River. Total dissolved solid concentrations measured in samples collected from the Devils River and Pecos River did not exceed the proposed State of Texas water-quality standard applicable for the segments of each river where samples were collected. During the spring and summer of 2005, chloride concentrations measured in samples collected in 2005 from the Devils River ranged from 11.6 to 12.9 mg/L, compared to chloride concentrations measured in samples collected from the Pecos River, which ranged from 519 to 879 mg/L. Chloride concentrations in samples collected from the Devils River in 2005 were less than the lower quartile (25th percentile) value of 14.0 mg/L reported for chloride concentrations in water-quality samples collected at the same sampling location during 1978–95 by the U.S. Geological Survey as part of the Hydrologic Benchmark Network program. The chloride concentrations measured in samples collected from the Pecos River during the spring and summer of 2005 represented a range of values similar to the interquartile range of 548 to 942 mg/L reported for samples collected during 1974–2007 at the same sampling location by the U.S. Geological Survey as part of the National Stream Quality Accounting Network program. None of the chloride concentrations measured in samples collected from the Devils or Pecos Rivers in 2005 exceeded applicable proposed State of Texas water-quality standards for chloride. Sulfate concentrations ranged from 7.55 to 8.20 mg/L in samples from the Devils River compared to 298 to 503 mg/L in samples from the Pecos River. Concentrations of sulfate did not exceed applicable proposed State of Texas water-quality standards. Ammonia plus organic nitrogen concentrations were reported as nitrogen ranged from 0.12 to 0.14 mg/L of nitrogen in samples collected from the Devils River compared to 0.15 to 0.32 mg/L of nitrogen in samples collected from the Pecos River. Ammonia plus organic nitrogen concentrations measured in samples collected from the Devils River in 2005 were less than the lower quartile (25th percentile) value of 0.23 mg/L of nitrogen for concentrations in water-quality samples collected at the same sampling location during 1978–95 by the U.S. Geological Survey as part of the Hydrologic Benchmark Network program. Ammonia plus nitrogen concentrations measured in samples collected from the Pecos River were similar to the range of historical concentrations measured in samples collected from the same Pecos River sampling location by the U.S. Geological Survey National Stream Quality Accounting Network program. Nitrate plus nitrite concentrations in samples from the Devils River and Pecos Rivers were within the historical range of concentrations for samples collected at the same locations on each river. Total phosphorous and orthophosphate concentrations were less than the laboratory reporting levels in the water samples from the Devils and Pecos Rivers. None of the selenium concentrations measured in samples collected during the spring and summer of 2005 from the Devils or Pecos Rivers exceeded the Texas Surface Water Quality Standards (chronic criterion of 5 μg/L or the acute criterion of 20 μg/L) established by the State for the protection of aquatic life. Concentrations of pesticides in the samples collected from the Devils and Pecos Rivers during March–August 2005 were very low and not present in detectable amounts (all reported concentrations were below laboratory reporting levels). The total number of fish species collected was the same in the Devils River and Pecos River, but the species found in the two rivers varied slightly. The number of fish species generally increased from the site farthest upstream to the site farthest downstream in the Devils River, and decreased between the site farthest upstream and site farthest downstream in the Pecos River. The redbreast sunfish was the most abundant species collected in the Devils River, and the blacktail shiner was the most abundant species collected in the Pecos River. Comparing the species from each river, the percentage of omnivorous fish species was larger at the more downstream sites closer to Amistad Reservoir, and the percentage of species tolerant of environmental stressors was larger in the Pecos River. The fish community, assessed on the basis of the number of shared species among the sites sampled, was more similar to the fish community at the other sites on the same river than it was to the fish community from any other site in the other river. More macroinvertebrate taxa were collected in the Devils River than in the Pecos River. The largest number of macroinvertebrate taxa were from the site second farthest downstream on the Devils River, and the smallest numbers of macroinvertebrate taxa were from the farthest downstream site on the Pecos River. Mayflies were more common in the Devils River, and caddisflies were less common than mayflies at most sites. Net-spinning caddisflies were more common at the Devils River sites. The combined percent of mayfly, caddisfly, and stonefly taxa was generally larger at the Pecos River sites. Riffle beetles were the most commonly collected beetle taxon among all sites, and water-penny beetles were only collected at the Pecos River sites. A greater number of true midge taxa were collected more than any other taxa at the genus and species taxonomic level. Non-insect macroinvertebrate taxa were more common at the Devils River sites. Corbicula sp. (presumably the introduced Asian clam) was found at sites in both rivers, and amphipods were more abundant in the Devils River. The Margalef species richness index, based on aquatic insect taxa only, was larger at the Devils River sites than at the Pecos River sites. The Hilsenhoff's biotic index was largest at the site farthest downstream in the Devils River and smallest at the site second farthest downstream in the Pecos River. Overall similarity among sites based on the number of shared macroinvertebrate taxa indicated that each site is more similar to other sites on the same river than to sites on the other river.

Texas↗

USGS2002

Influence of eastern hemlock (Tsuga canadensis) forests on aquatic invertebrate assemblages in headwater streams

We conducted a comparative study in the Delaware Water Gap National Recreation Area to determine the potential long-term impacts of hemlock forest decline on stream benthic macroinvertebrate assemblages. Hemlock forests throughout eastern North America have been declining because of the hemlock woolly adelgid, an exotic insect pest. We found aquatic invertebrate community structure to be strongly correlated with forest composition. Streams draining hemlock forests supported significantly more total taxa than streams draining mixed hardwood forests, and over 8% of the taxa were strongly associated with hemlock. In addition, invertebrate taxa were more evenly distributed (i.e., higher Simpson's evenness values) in hemlock-drained streams. In contrast, the number of rare species and total densities were significantly lower in streams draining hemlock, suggesting that diversity differences observed between forest types were not related to stochastic factors associated with sampling and that streams draining mixed hardwood forests may be more productive. Analysis of stream habitat data indicated that streams draining hemlock forests had more stable thermal and hydrologic regimes. Our findings suggest that hemlock decline may result in long-term changes in headwater ecosystems leading to reductions in both within-stream (i.e., alpha) and park-wide (i.e., gamma) benthic community diversity.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2004

Diets of insectivorous birds along the Colorado River in Grand Canyon, Arizona

We examined diets of six insectivorous bird species ( n = 202 individuals) from two vegetation zones along the Colorado River in Grand Canyon National Park, Arizona, 1994. All bird species consumed similar quantities of caterpillars and beetles, but use of other prey taxa varied. Non-native leafhoppers ( Opsius stactagolus ) specific to non-native tamarisk ( Tamarix chinensis ) substantially augmented Lucy's Warbler ( Vermivora luciae ) diets (49%), while ants comprised 82% of Yellow-breasted Chat ( Icteria virens ) diets. Yellow Warbler ( Dendroica petechia ) diets were composed of 45% aquatic midges. All bird species consumed the non-native leafhopper specific to tamarisk. Comparison of bird diets with availability of arthropod prey from aquatic and terrestrial origins showed terrestrial insects comprised 91% of all avian diets compared to 9% of prey from aquatic origin. Seasonal shifts in arthropod prey occurred in diets of three bird species, although no seasonal shifts were detected in arthropods sampled in vegetation indicating that at least three bird species were not selecting prey in proportion to its abundance. All bird species had higher prey overlap with arthropods collected in the native, mesquite-acacia vegetation zone which contained higher arthropod diversity and better prey items (i.e., Lepidoptera). Lucy's Warbler and Yellow Warbler consumed high proportions of prey items found in greatest abundance in the tamarisk-dominated vegetation zone that has been established since the construction of Glen Canyon Dam. These species appeared to exhibit ecological plasticity in response to an anthropogenic increase in prey resources.

Arizona↗

USGS2023

Ecotoxicological studies indicate that sublethal and lethal processes limit insect-mediated contaminant flux

Merolimnic insects can accumulate and transport considerable amounts of aquatic contaminants to terrestrial systems. The rate of contaminant biotransport, termed insect-mediated contaminant flux (IMCF), depends on emergent insect biomass and contaminant accumulation, both functions of environmental concentration. Here we develop a mathematical model of IMCF and apply it to three ecotoxicological studies obtained through the U.S. Environmental Protection Agency's ECOTOX database to determine at which concentration maximum IMCF occurs. Model results demonstrate that the maximum IMCF depends on competing rates of biomass loss and contaminant accumulation and does not necessarily occur at the highest insect or environmental contaminant concentration. Additionally, modeling results suggest that sublethal contaminant effects (e.g., decreased growth) on insect biomass can be an important and potentially underappreciated control on IMCF.

Environmental Toxicology and Chemistry↗

USGS2015

Air- and stream-water-temperature trends in the Chesapeake Bay region, 1960-2014

Water temperature is a basic, but important, measure of the condition of all aquatic environments, including the flowing waters in the streams that drain our landscape and the receiving waters of those streams. Climatic conditions have a strong influence on water temperature, which is therefore naturally variable both in time and across the landscape. Changes to natural water-temperature regimes, however, can result in a myriad of effects on aquatic organisms, water quality, circulation patterns, recreation, industry, and utility operations. For example, most species of fish, insects, and other organisms, as well as aquatic vegetation, are highly dependent on water temperature. Warming waters can result in shifts in floral and faunal species distributions, including invasive species and pathogens previously unable to inhabit the once cooler streams. Many chemical processes are temperature dependent, with reactions occurring faster in warmer conditions, leading to degraded water quality as contaminants are released into waterways at greater rates. Circulation patterns in receiving waters, such as bays and estuaries, can change as a result of warmer inflows from streams, thereby affecting organisms in those receiving waters. Changes in abundance of some aquatic species and (or) degradation of water quality can reduce the recreational value of water bodies as waters are perceived as less desirable for water-related activities or as sportfish become less available for anglers. Finally, increasing water temperatures can affect industry and utilities as the thermal capacity is reduced, making the water less effective for cooling purposes. Chesapeake Bay is the largest estuary in the United States. Eutrophication, the enrichment of a water body with excess nutrients, has plagued the bay for decades and has led to extensive restoration efforts throughout the bay watershed. The warming of stream water can exacerbate eutrophication through increased release of nutrients from in-stream sediments, so understanding changes in stream-water temperature throughout the bay watershed is critical to resource managers seeking to restore the bay ecosystem. The U.S. Environmental Protection Agency (EPA) uses indicators that “represent the state or trend of certain environmental or societal conditions … to track and better understand the effects of changes in the Earth’s climate” (U.S. Environmental Protection Agency, 2014). Updates to these indicators are published biennially by the EPA. The U.S. Geological Survey (USGS), in cooperation with the EPA, has completed analyses of air- and stream-water-temperature trends in the Chesapeake Bay region to be included as an indicator in a future release of the EPA report.

Delaware, Maryland, New York, Pennsylvania, Virgin↗

USGS1987

Macrofauna and environment of the Nanpil-Kiepw River, Ponape, Eastern Caroline Islands

The first comprehensive evaluation of stream fauna in the Eastern Caroline Islands resulted from collections on Ponape, a 334-km- island having more than 40 streams, many of which arise along 700-m-high interior ridges. Field surveys centered on the Nanpil-Kiepw River below 170 m elevation, a bouldery reach with water of low mineral content and frequent surging flows. Faunal specimens were collected by electrofishing, rotenone treatment, netting, and hand picking. Discharge character of the Nanpil-Kiepw River is similar to but more extreme than that of other streams of Oceania with which it was compared. Drastic flow surges appeared to be a major factor affecting community structure. At least 44 faunal species were present, 36 of them representing taxons primarily of marine origin that are characteristic of oceanic islands: 15 fishes (5 families), 10 decapod crustaceans (3 families), and 11 snails (2 families). Larvae of aquatic moths were the only insects of significance. Four sicydiine gobies are new species possibly endemic to Ponape or the Eastern Caroline Islands. Based on numbers of species within prominent taxons and diadromous groups, Ponape’s faunal diversity exceeds that of Samoa, Guam, and Hawaii, but is lower than that of Palau. Similarities of Ponape's identified fish species to those of Palau suggest that Ponape was colonized from the west along the “Caroline conduit.”

Pohnpei↗