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At least 937 records · Page 52Linked to original sources
USGS1996

Uncertainty and instream flow standards

Several years ago, Science published an important essay (Ludwig et al. 1993) on the need to confront the scientific uncertainty associated with managing natural resources. The essay did not discuss instream flow standards explicitly, but its arguments apply. At an April 1995 workshop in Davis, California, all 12 participants agreed that currently no scientifically defensible method exists for defining the instream flows needed to protect particular species of fish or aquatic ecosystems (Williams, in press). We also agreed that acknowledging this fact is an essential step in dealing rationally and effectively with the problem. Practical necessity and the protection of fishery resources require that new instream flow standards be established and that existing standards be revised. However, if standards cannot be defined scientifically, how can this be done? We join others in recommending the approach of adaptive management. Applied to instream flow standards, this approach involves at least three elements.

Fisheries↗
USGS2007

Testing tail-mounted transmitters with Myocastor coypus (nutria)

We developed a tail-mounted radio-transmitter for Myocastor coypus (nutria) that offers a practical and efficient alternative to collar or implant methods. The mean retention time was 96 d (range 57-147 d, n = 7), making this a practical method for short-term studies. The tail-mounts were less injurious to animals than collars and easier for field researchers to implement than either collars or surgically implanted transmitters.

Southeastern Naturalist↗
USGS2021

Preface to book: Wetland carbon and environmental management

The idea for this book, including its organization and contents, has its origin in the latest environmental and climate policy requirements in the United States, as well as science advances. In 2007, the U.S. Congress passed the Energy Independence and Security Act (EISA), from which Section 712 required U.S. Federal agencies to provide a better understanding of carbon and greenhouse gas fluxes across the United States. As a result, largescale and coordinated efforts were launched to assess carbon storage, carbon fluxes, and greenhouse gas fluxes including CO2, CH4, and N2O from all major terrestrial and freshwater aquatic ecosystems, including forest, grassland/shrub, agricultural lands, wetlands, and rivers, streams, lakes, and impoundments. The EISA assessment produced major results (Selmants et al., 2017; Zhu, 2011; Zhu & McGuire, 2016; Zhu & Reed, 2012, 2014), but recognized that wetlands remained a significant source of uncertainty, especially for those wetlands that were being actively managed. The more recent Second State of the Carbon Cycle Report by the U.S. Global Change Research Program (USGCRP), which devoted two separate chapters to inland and coastal wetlands, respectively, noted that large knowledge gaps still remain, ranging from inadequate analysis of restored and managed wetlands, and consequences of management decisions, to future wetland responses to climate change (USGCRP, 2018). In recent literature, wetland management is suggested as a potential natural solution to mitigate climate change (Fargione et al., 2018, Kroeger et al., 2017) and help offset direct losses of wetlands from sea level rise, subsidence, and coastal erosion (Wang et al., 2017). The recognition that a synthesis of wetland carbon management was urgently needed was the genesis of Wetland Carbon and Environmental Management; discerning the relationships between wetland management and carbon flux (loss or gain) is an international goal.

Geophysical Monograph Series↗
USGS1987

Phytoplankton productivity in relation to light intensity: A simple equation

A simple exponential equation is used to describe photosynthetic rate as a function of light intensity for a variety of unicellular algae and higher plants where photosynthesis is proportional to (1-e −β1 ). The parameter β ( =I k −1 "> =I k −1 ) is derived by a simultaneous curve-fitting method, where I is incident quantum-flux density. The exponential equation is tested against a wide range of data and is found to adequately describe P vs. I curves. The errors associated with photosynthetic parameters are calculated. A simplified statistical model (Poisson) of photon capture provides a biophysical basis for the equation and for its ability to fit a range of light intensities. The exponential equation provides a non-subjective simultaneous curve fitting estimate for photosynthetic efficiency ( a ) which is less ambiguous than subjective methods: subjective methods assume that a linear region of the P vs. I curve is readily identifiable. Photosynthetic parameters β and a are used widely in aquatic studies to define photosynthesis at low quantum flux. These parameters are particularly important in estuarine environments where high suspended-material concentrations and high diffuse-light extinction coefficients are commonly encountered.

Estuarine, Coastal and Shelf Science↗
USGS2022

Potential health effects of contaminant mixtures from point and nonpoint sources on fish and frogs in the New Jersey Pinelands

Aquatic ecosystems convey complex contaminant mixtures from anthropogenic pollution on a global scale. Point (e.g., municipal wastewater) and nonpoint sources (e.g., stormwater runoff) are both drivers of contaminant mixtures in aquatic habitats. The objectives of this study were to identify the contaminant mixtures present in surface waters impacted by both point and nonpoint sources, to determine if aquatic biota (amphibian and fish) health effects (testicular oocytes and parasites) occurred at these sites, and to understand if differences in biological and chemical measures existed between point (on-stream) and nonpoint sources (off-stream). To accomplish this, water chemistry, fishes, and frogs were collected from 21 sites in the New Jersey Pinelands, United States. Off-stream sites consisted of 3 reference and 10 degraded wetlands. On-stream sites consisted of two reference lakes and six degraded steams/lakes (four sites above and two sites below wastewater outfalls). Surface water was collected 4 times at each site and analyzed for 133 organic and inorganic contaminants. One native and five non-native fish species were collected from streams/lakes and native green frogs from wetlands (ponds and stormwater basins). Limited differences in contaminant concentrations were observed in reference and degraded wetlands but for streams/lakes, results indicated that landscape alteration, (upland agricultural and developed land) was the primary driver of contaminant concentrations rather than municipal wastewater. Incidence of estrogenic endocrine disruption (intersex) was species dependent with the highest prevalence observed in largemouth bass and black crappie and the lowest prevalence observed in green frogs and tessellated darters. Parasite prevalence was site and species dependent. Prevalence of eye parasites increased with increasing concentrations of industrial, mycotoxin, and cumulative inorganic contaminants. These findings are critical to support the conservation, protection, and management of a wide range of aquatic species in the Pinelands and elsewhere as habitat loss, alteration, and fragmentation increase with increasing development.

New Jersey↗
USGS2023

Biogeochemical and hydrologic synergy control mercury fate in an arid land river-reservoir system

Reservoirs in arid landscapes provide critical water storage and hydroelectric power but influence the transport and biogeochemical cycling of mercury (Hg). Improved management of reservoirs to mitigate the supply and uptake of bioavailable methylmercury (MeHg) in aquatic food webs will benefit from a mechanistic understanding of inorganic divalent Hg (Hg( II )) and MeHg fate within and downstream of reservoirs. Here, we quantified Hg( II ), MeHg, and other pertinent biogeochemical constituents in water (filtered and associated with particles) at high temporal resolution from 2016–2020. This was done (1) at inflow and outflow locations of three successive hydroelectric reservoirs (Snake River, Idaho, Oregon) and (2) vertically and longitudinally within the first reservoir (Brownlee Reservoir). Under spring high flow, upstream inputs of particulate Hg (Hg( II ) and MeHg) and filter-passing Hg( II ) to Brownlee Reservoir were governed by total suspended solids and dissolved organic matter, respectively. Under redox stratified conditions in summer, net MeHg formation in the meta- and hypolimnion of Brownlee reservoir yielded elevated filter-passing and particulate MeHg concentrations, the latter exceeding 500 ng g −1 on particles. Simultaneously, the organic matter content of particulates increased longitudinally in the reservoir (from 9–29%) and temporally with stratified duration. In late summer and fall, destratification mobilized MeHg from the upgradient metalimnion and the downgradient hypolimnion of Brownlee Reservoir, respectively, resulting in downstream export of elevated filter-passing MeHg and organic-rich particles enriched in MeHg (up to 43% MeHg). We document coupled biogeochemical and hydrologic processes that yield in-reservoir MeHg accumulation and MeHg export in water and particles, which impacts MeHg uptake in aquatic food webs within and downstream of reservoirs.

Environmental Science: Processes & Impacts↗
USGS2010

The areal extent of brown shrimp habitat suitability in Mobile Bay, Alabama, USA: Targeting vegetated habitat restoration

The availability of wetlands and shallow water habitats significantly influences Gulf of Mexico (GOM) penaeid shrimp fishery productivity. However, the GOM region has the highest rate of wetland loss in the USA. Protection and management of these vital GOM habitats are critical to sustainable shrimp fisheries. Brown shrimp (Farfantepenaeus aztecus) are a major component of GOM fisheries. We present an approach for estimating the areal extent of suitable habitat for post-larval and juvenile brown shrimp in Mobile Bay, Alabama, using an existing habitat suitability index model for the northern GOM calculated from probabilistic survey of water quality and sediment data, land cover data, and submerged aquatic vegetation coverages. This estuarine scale approach is intended to support targeted protection and restoration of these habitats. These analyses indicate that approximately 60% of the area of Mobile Bay is categorized as suitable to near optimal for post-larval and juvenile shrimp and 38% of the area is marginally to minimally suitable. We identify potential units within Mobile Bay for targeted restoration to improve habitat suitability. ?? 2010 Springer Science+Business Media B.V.

Environmental Monitoring and Assessment↗
USGS2019

Mixed-chemical exposure and predicted effects potential in wadeable southeastern USA streams

Complex chemical mixtures have been widely reported in larger streams but relatively little work has been done to characterize them and assess their potential effects in headwaterstreams. In 2014, the United States Geological Survey (USGS) sampled 54 Piedmont streams over ten weeks and measured 475 unique organic compounds using five analytical methods. Maximum and median exposure conditions were evaluated in relation to watershed characteristics and for potential biological effects using multiple lines of evidence. Results demonstrate that mixed-contaminant exposures are ubiquitous and varied in sampled headwater streams. Approximately 56% (264) of the 475 compounds were detected at least once across all sites. Cumulative maximum concentrations ranged 1,922–162,346 ng L −1 per site. Chemical occurrence significantly correlated to urban land use but was not related to presence/absence of wastewater treatment facility discharges. Designed bioactive chemicals represent about 2/3rd of chemicals detected, notably pharmaceuticals and pesticides, qualitative evidence for possible adverse biological effects. Comparative Toxicogenomics Database chemical-gene associations applied to maximum exposure conditions indicate >12,000 and 2,900 potential gene targets were predicted at least once across all sites for fish and invertebrates, respectively. Analysis of cumulative exposure-activity ratios provided additional evidence that, at a minimum, transient exposures with high probability of molecular effects to vertebrates were common. Finally, cumulative detections and concentrations correlated inversely with invertebrate metrics from in-stream surveys. The results demonstrate widespread instream exposure to extensive contaminant mixtures and compelling multiple lines of evidence for adverse effects on aquatic communities.

Science of the Total Environment↗
USGS2021

Groundwater discharges as a source of phytoestrogens and other agriculturally derived contaminants to streams

Groundwater discharge zones in streams are important habitats for aquatic organisms. The use of discharge zones for thermal refuge and spawning by fish and other biota renders them susceptible to potential focused discharge of groundwater contamination. Currently, there is a paucity of information about discharge zones as a potential exposure pathway of chemicals to stream ecosystems. Using thermal mapping technologies to locate groundwater discharges, shallow groundwater and surface water from three rivers in the Chesapeake Bay Watershed, USA were analyzed for phytoestrogens, pesticides and their degradates, steroid hormones, sterols and bisphenol A. A Bayesian censored regression model was used to compare groundwater and surface water chemical concentrations. The most frequently detected chemicals in both ground and surface water were the phytoestrogens genistein (79%) and formononetin (55%), the herbicides metolachlor (50%) and atrazine (74%), and the sterol cholesterol (88%). There was evidence suggesting groundwater discharge zones could be a unique exposure pathway of chemicals to surface water systems, in our case, metolachlor sulfonic acid (posterior mean concentration = 150 ng/L in groundwater and 4.6 ng/L in surface water). Our study also demonstrated heterogeneity of chemical concentration in groundwater discharge zones within a stream for the phytoestrogen formononetin, the herbicides metolachlor and atrazine, and cholesterol. Results support the hypothesis that discharge zones are an important source of exposure of phytoestrogens and herbicides to aquatic organisms. To manage critical resources within the Chesapeake Bay Watershed, more work is needed to characterize exposure in discharge zones more broadly across time and space.

Delaware, Maryland, New Jersey, New York, Pennsylv↗
USGS2008

Molecular and structural characterization of dissolved organic matter from the deep ocean by FTICR-MS, including hydrophilic nitrogenous organic molecules

Dissolved organic matter isolated from the deep Atlantic Ocean and fractionated into a so-called hydrophobic (HPO) fraction and a very hydrophilic (HPI) fraction was analyzed for the first time by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to resolve the molecular species, to determine their exact masses, and to calculate their molecular formulas. The elemental composition of about 300 molecules was identified. Those in the HPO fraction (14C age of 5100 year) are very similar to much younger freshwater fulvic acids, but less aromatic and more oxygenated molecules are more frequent. This trend continues toward the HPI fraction and may indicate biotic and abiotic aging processes that this material experienced since its primary production thousands of years ago. In the HPI fraction series of nitrogenous molecules containing one, two, or three nitrogens were identified by FTICR-MS. Product ion spectra of the nitrogenous molecules suggest that the nitrogen atoms in these molecules are included in the (alicyclic) backbone of these molecules, possibly in reduced form. These mass spectrometric data suggest that a large set of stable fulvic acids is ubiquitous in all aquatic compartments. Although sources may differ, their actual composition and structure appears to be quite similar and largely independent from their source, because they are the remainder of intensive oxidative degradation processes. ?? 2008 American Chemical Society.

Environmental Science & Technology↗
USGS2024

Fish conservation in streams of the agrarian Mississippi Alluvial Valley: Conceptual model, management actions, and field verification

The effects of agriculture and flood control practices accrued over more than a century have impaired aquatic habitats and their fish communities in the Mississippi Alluvial Valley, the historic floodplain of the Lower Mississippi River prior to leveeing. As a first step to conservation planning and adaptive management, we developed and tested a conceptual model of how changes to this floodplain have affected stream environments and fish assemblages. The model is deliberately simple in structure because it needs to be understood by stakeholders ranging from engineers to farmers who must remain engaged to ensure effective conservation. Testing involved multivariate correlative analyses that included descriptors of land setting, water quality, and fish assemblages representing 376 stream samples taken over two decades and ranging in Strahler stream order from 1 to 8. The conceptual model was adequately corroborated by empirical data, but with unexplained variability that is not uncommon in field surveys where gear biases, temporal biases, and scale biases prevent accurate characterizations. Our conceptual model distinguishes three types of conservation actions relevant to large agricultural floodplains: reforestation of large parcels and riparian zone conservation, in-channel interventions and connectivity preservation, and flow augmentation. Complete restoration of the floodplain may not be an acceptable option to the agriculture community. However, in most cases the application of even the most basic measures can support the return of sensitive aquatic species. We suggest that together these types of conservation actions can bring improved water properties to impacted reaches, higher reach biodiversity, more intolerant species, and more rheophilic fishes.

Mississippi Alluvial Valle↗
USGS2016

Endocrine disrupting activities of surface water associated with a West Virginia oil and gas industry wastewater disposal site

Currently, >95% of end disposal of hydraulic fracturing wastewater from unconventional oil and gas operations in the US occurs via injection wells. Key data gaps exist in understanding the potential impact of underground injection on surface water quality and environmental health. The goal of this study was to assess endocrine disrupting activity in surface water at a West Virginia injection well disposal site. Water samples were collected from a background site in the area and upstream, on, and downstream of the disposal facility. Samples were solid-phase extracted, and extracts assessed for agonist and antagonist hormonal activities for five hormone receptors in mammalian and yeast reporter gene assays. Compared to reference water extracts upstream and distal to the disposal well, samples collected adjacent and downstream exhibited considerably higher antagonist activity for the estrogen, androgen, progesterone, glucocorticoid and thyroid hormone receptors. In contrast, low levels of agonist activity were measured in upstream/distal sites, and were inhibited or absent at downstream sites with significant antagonism. Concurrent analyses by partner laboratories (published separately) describe the analytical and geochemical profiling of the water; elevated conductivity as well as high sodium, chloride, strontium, and barium concentrations indicate impacts due to handling of unconventional oil and gas wastewater. Notably, antagonist activities in downstream samples were at equivalent authentic standard concentrations known to disrupt reproduction and/or development in aquatic animals. Given the widespread use of injection wells for end-disposal of hydraulic fracturing wastewater, these data raise concerns for human and animal health nearby.

Science of the Total Environment↗
USGS2026

Advancing monitoring approaches to enhance tidal Chesapeake Bay habitat assessment for submerged aquatic vegetation, water clarity, chlorophyll a and dissolved oxygen

Water quality monitoring capacity has been declining for the Chesapeake Bay Program (CBP) at a time when information needs are growing, and data gaps exist to address critical decision-support for managers. The CBP Scientific Technical Assessment and Reporting Team is leading a Principal’s Staff Committee requested gap analyses toward understanding support needed to improve water quality monitoring and analysis programming. Advanced technologies and alternative monitoring approaches in the form of satellite-based measurements, Artificial Intelligence/Machine Learning (AI/ML) algorithms for data interpretation, continuous water quality in-situ sensor arrays, and community science efforts offer a growing portfolio of valuable opportunities for expanding data collections and analysis program capacities. However, since 1985, each of these options are examples of growing opportunities to enhance water quality assessments yet has seen limited adoption into elements of Chesapeake Bay water quality monitoring programs. Where new technologies have been adopted (e.g., shallow water continuous water quality monitoring), such temporally rich data streams have supported Bay health insights yet had limited use in regulatory water quality criteria assessment. This Scientific Technical Advisory Committee (STAC) supported workshop provided the ideal forum for engaging our CBP partnership regarding the maturity of new and evolving monitoring and analysis capacities to address program information needs while appreciating limitations with adopting new tools and approaches. Improving natural resources monitoring efficiency and effectiveness will expand the scientific and technical foundations for making robust, strategic choices on decisions for CBP Partnership community-based priorities, policies, and management actions. Workshop findings and recommendations reflect progress in science, technology, and analyses addressing long-standing programmatic limitations in data collection and analysis capacities. State-of-the-science updates highlighted in the workshop span the spectrum of efforts representing improvements, successes, remaining challenges toward operationalizing protocols, and guidance toward research, or adoption and implementation by monitoring programs.

Maryland, Pennsylvania, Virginia↗
USGS2025

Selenium differentially influences methylmercury retention across mayfly life stages

Though high mercury and selenium concentrations are individually toxic to organisms, there is a hypothesized antagonistic relationship. This potential mercury–selenium interaction is under-studied in aquatic macroinvertebrates, particularly in relation to complex life histories. We examined the proposed effect of selenium on methylmercury accumulation between four life stages for a parthenogenetic mayfly ( Neocloeon triangulifer ). We exposed diatoms to elevated methylmercury concentrations and fed them to mayflies exposed to elevated aqueous selenomethionine. We found some support for the mercury–selenium antagonism hypothesis, but it was context-specific. Selenium reduced methylmercury accumulation in high but not low methylmercury environments. Though terrestrial adult life stages had higher mercury concentrations compared to aquatic larval life stages, cumulative life history transfer factor (LHTF; ratio of methylmercury in adult imago to late instar larvae) differed by treatment. LHTF was constant for all aqueous selenium exposure levels at high dietary methylmercury (selenium impacts on methylmercury uptake and loss) but increased with aqueous selenium exposures at low dietary methylmercury (selenium impacts on methylmercury uptake only), suggesting a synergistic enhancement of MeHg transfer between life stages with increased aqueous Se exposure levels. These results suggest that animals eating adult aquatic insects are exposed to higher concentrations of methylmercury than those feeding on larval insects across selenium and methylmercury levels, but interference of selenium on methylmercury accumulation is only present at high methylmercury environments.

Environmental Science and Technology↗
USGS2017

Case studies of riparian and watershed restoration in the southwestern United States—Principles, challenges, and successes

Globally, rivers and streams are highly altered by impoundments, diversions, and stream channelization associated with agricultural and water delivery needs. Climate change imposes additional challenges by further reducing discharge, introducing variability in seasonal precipitation patterns, and increasing temperatures. Collectively, these changes in a river or stream’s annual hydrology affects surface and groundwater dynamics, fluvial processes, and the linked aquatic and riparian responses, particularly in arid regions. Recognizing the inherent ecosystem services that riparian and aquatic habitats provide, society increasingly supports restoring the functionality of riparian and aquatic ecosystems. Given the wide range in types and scales of riparian impacts, approaches to riparian restoration can range from tactical, short-term, and site-specific efforts to strategic projects and long-term collaborations best pursued at the watershed scale. In the spirit of sharing information, the U.S. Geological Survey’s Grand Canyon Monitoring and Research Center convened a workshop June 23-25, 2015, in Flagstaff, Ariz. for practitioners in restoration science to share general principles, successful restoration practices, and discuss the challenges that face those practicing riparian restoration in the southwestern United States. Presenters from the Colorado River and the Rio Grande basins, offered their perspectives and experiences in restoration at the local, reach and watershed scale. Outcomes of the workshop include this Proceedings volume, which is composed of extended abstracts of most of the presentations given at the workshop, and recommendations or information needs identified by participants. The organization of the Proceedings follows a general progression from local scale restoration to river and watershed scale approaches, and finishes with restoration assessments and monitoring.

Open-File Report↗
USGS2024

Riparian methylmercury production increases riverine mercury flux and food web concentrations

The production and uptake of toxic methylmercury (MeHg) impacts aquatic ecosystems globally. Rivers can be dynamic and difficult systems to study for MeHg production and bioaccumulation, hence identifying sources of MeHg to these systems is both challenging and important for resource management within rivers and main-stem reservoirs. Riparian zones, which are known biogeochemical hotspots for MeHg production, are understudied as potential sources of MeHg to rivers. Here, we present a comprehensive quantification of the hydrologic and biogeochemical processes governing MeHg concentrations, loads, and bioaccumulation at 16 locations along 164 km of the agriculturally intensive Snake River (Idaho, Oregon USA) during summer baseflow conditions, with emphasis on riparian production of MeHg. Approximately one-third of the MeHg load of the Snake River could not be attributed to inflowing waters (upgradient, tributaries, or irrigation drains). Across the study reach, increases in MeHg loads in surface waters were significantly correlated with MeHg concentrations in riparian porewaters, suggesting riparian zones were likely an important source of MeHg to the Snake River. Across all locations, MeHg concentrations in surface waters positively correlated with MeHg concentrations in benthic snails and clams, supporting that riparian produced MeHg was assimilated into local aquatic food webs. This study contributes new insights into riparian MeHg production within rivers which can inform mitigation efforts to reduce MeHg bioaccumulation in fish.

Idaho, Oregon↗
USGS2018

Hydrologic characteristics of freshwater mussel habitat: novel insights from modeled flows

The ability to model freshwater stream habitat and species distributions is limited by the spatially sparse flow data available from long-term gauging stations. Flow data beyond the immediate vicinity of gauging stations would enhance our ability to explore and characterize hydrologic habitat suitability. The southeastern USA supports high aquatic biodiversity, but threats, such as landuse alteration, climate change, conflicting water-resource demands, and pollution, have led to the imperilment and legal protection of many species. The ability to distinguish suitable from unsuitable habitat conditions, including hydrologic suitability, is a key criterion for successful conservation and restoration of aquatic species. We used the example of the critically endangered Tar River Spinymussel ( Parvaspina steinstansana ) and associated species to demonstrate the value of modeled flow data (WaterFALL™) to generate novel insights into population structure and testable hypotheses regarding hydrologic suitability. With ordination models, we: 1) identified all catchments with potentially suitable hydrology, 2) identified 2 distinct hydrologic environments occupied by the Tar River Spinymussel, and 3) estimated greater hydrological habitat niche breadth of assumed surrogate species associates at the catchment scale. Our findings provide the first demonstrated application of complete, continuous, regional modeled hydrologic data to freshwater mussel distribution and management. This research highlights the utility of modeling and data-mining methods to facilitate further exploration and application of such modeled environmental conditions to inform aquatic species management. We conclude that such an approach can support landscape-scale management decisions that require spatial information at fine resolution (e.g., enhanced National Hydrology Dataset catchments) and broad extent (e.g., multiple river basins).

North Carolina↗
USGS2023

Identifying invertebrate indicators for streamflow duration assessments in forested headwater streams

Streamflow-duration assessment methods (SDAMs) are rapid, indicator-based tools for classifying streamflow duration (e.g., intermittent vs perennial flow) at the reach scale. Indicators are easily assessed stream properties used as surrogates of flow duration, which is too resource intensive to measure directly for many reaches. Invertebrates are commonly used as SDAM indicators because many are not highly mobile, and different species have life stages that require flow for different durations and times of the year. The objectives of this study were to 1) identify invertebrate taxa that can be used as SDAM indicators to distinguish between stream reaches having intermittent and perennial flow, 2) to compare indicator strength across different taxonomic and numeric resolutions, and 3) to assess the relative importance of season and habitat type on the ability of invertebrates to predict streamflow-duration class. We used 2 methods, random forest models and indicator species analysis, to analyze aquatic and terrestrial invertebrate data (presence/absence, density, and biomass) at the family and genus levels from 370 samples collected from both erosional and depositional habitats during both wet and dry seasons. In total, 36 intermittent and 53 perennial reaches were sampled along 31 forested headwater streams in 4 level II ecoregions across the United States. Random forest models for family- and genus-level datasets had stream classification accuracy ranging from 88.9 to 93.2%, with slightly higher accuracy for density than for presence/absence and biomass datasets. Season (wet/dry) tended to be a stronger predictor of streamflow-duration class than habitat (erosional/depositional). Many taxa at the family (58.8%) and genus level (61.6%) were collected from both intermittent and perennial reaches, and most taxa that were exclusive to 1 streamflow-duration class were rarely collected. However, 23 family-level or higher taxa (20 aquatic and 3 terrestrial) and 44 aquatic genera were identified as potential indicators of streamflow-duration class for forested headwater streams. The utility of the potential indicators varied across level II ecoregions in part because of representation of intermittent and perennial reaches in the dataset but also because of variable ecological responses to drying among species. Aquatic invertebrates have been an important field indicator of perennial reaches in existing SDAMs, but our findings highlight how including aquatic and terrestrial invertebrates as indicators of intermittent reaches can further maximize the data collected for streamflow-duration classifications.

Freshwater Science↗