Associations between adult caddisfly species (Insecta: Trichoptera) and stream conditions within the northcentral United States

The Oregon Coast Range, rich in natural resources, is under increasing pressure from rapid development. The purpose of this study was to examine diatom species patterns in relation to environmental variables in streams of this region. Diatoms, water quality, physical habitat and watershed characteristics were assessed for 33 randomly selected stream sites. Watershed size, elevation, geology, vegetation and stream morphology varied substantially among sites. Streams were characterized by dilute water chemistry and a low percent of fine substrate. A total of 80 diatom taxa were identified. Taxa richness was low throughout the region (median 15, range 10–26). Assemblages were dominated by two adnate species, Achnanthidium minutissimum and Achnanthes pyrenaicum. Diatoms sensitive to organic pollution dominated the assemblages at all sites (median 85%). Non-metric multidimensional scaling (NMDS) and correlational analysis showed quantitative relationships between diatom assemblages and environmental variables. NMDS axes were significantly correlated with watershed area, watershed geology, conductivity, total nitrogen, total solids and stream width. Diatom-based site classification (Two-way Indicators Species Analysis, (TWINSPAN)) yielded 4 discrete groups that displayed weak correlations with environmental variables. When stream sites were classified by dominant watershed geology, overall diatom assemblages between groups were significantly different (Analysis of Similarity (ANOSIM) global R = 0.19, p < 0.05). Our results suggest that streams in the coastal region are in relatively good condition. High natural variability in stream conditions in the Oregon Coast Range ecoregion may obscure quantitative relationships between environmental variables and diatom assemblages. A bioassessment protocol that classifies sites by major landscape variables and selects streams along the major human disturbance gradient might allow for detection of early signs of human disturbance in environmentally heterogeneous regions, such as the Pacific Northwest.

The adult stage of Trichoptera is valuable for assessing the biotic integrity of streams; however, it is not clear which specific metric(s) have the greatest value for doing so. In this study, >500,000 adult caddisfly specimens reflecting 299 species were sampled and identified from 903 stream sites throughout the northcentral United States. Specimen data were compiled into 31 water quality metrics encompassing taxonomic richness, diversity indices, pollution tolerance, percent dominant taxa, and relative abundance of functional feeding groups. Each metric was individually tested for its ability to predict the known percentage of undisturbed habitat upstream of each sampling site using simple linear regression modeling. Most metrics were statistically significant but had R2 values <0.30. The highest performing models were taxonomic richness at the species (R2 = 0.40), genus (0.52), and family (0.59) levels and the Hilsenhoff Biotic Index (HBI) (0.37). The family level of taxonomic resolution produced models with a higher R2 value than genus or species for all four of the metrics where taxonomic resolution was tested. Multiple linear regression models of all 31 metrics (R2 = 0.65) and of combined family richness, HBI, and the ratio of shredders to filtering collectors (0.62) exhibited modest improvements over using family richness exclusively. These results indicated that simple taxonomic richness metrics constitute the most effective predictors of undisturbed upstream habitat when using adult caddisfly data, and that family richness may be the most effective of all due to low stochastic variation and ease of use.

Low dissolved oxygen (DO) concentrations in streams can be linked to both natural conditions and human activities. In Louisiana, natural stream conditions such as low flow, high temperature and high organic content, often result in DO levels already below current water quality criteria, making it difficult to develop standards for Best Management Practices (BMPs). Along three low-order streams within a West Gulf Coastal Plain watershed in central Louisiana, streamflow conditions, temperature, organic carbon and DO were measured for one year in order to: (1) investigate spatial and seasonal differences in dissolved oxygen, (2) determine factors influencing the temperature dependence of DO concentrations, and (3) assess consequences of high temperature and organic content on dissolved oxygen levels downstream at higher order streams. Streamflow was measured and monthly water samples were collected at 11 locations. Water samples were analyzed for total and dissolved organic carbon. Stream temperature and dissolved oxygen were measured monthly in-situ at each location. The results show overall oxygen depletion in most of the sampled streams. There was a wide range of monthly DO levels (0.4 to 9.0 mg L-1) with the lowest levels generally occurring from May to July. On average, DO levels at the sites varied from 2.0 to 6.1 mg L-1. The stream site with the lowest average total organic carbon (7.74 mg L-1) also showed DO meeting TMDL standards (=5 mg L-1). This site, located near the headwaters of Spring Creek, is impacted the least by organic material transported downstream. There was a close relationship between organic carbon and dissolved oxygen, which appeared to be further affected by stream hydrologic conditions. In the forest-dominated landscape of central Louisiana, it may not be possible to reduce nutrient concentrations sufficiently to limit dissolved oxygen consumption, implying that existing water quality standards may not adequately address natural conditions.

Diatoms have been proven to be good indicators of natural stream conditions, but little is known about the seasonal variability of diatom communities in megacity streams. We investigated the spatial and temporal variation of diatom communities along an urban-to-rural gradient in megacity streams, Beijing, China. We found that the composition and diversity of diatom community was significantly different along the urban-to-rural gradient in streams of Beijing city. The diatom community was subtle temporal variation in the reference stream and urban upstream, but the temporal variation of diatoms was relatively greater in the urban downstream. Overall, the composition of the diatom community was relatively stable in the streams among different seasons, and the dominant species did not change much over seasons. For example, during the sampling periods, the species Achnanthidium minutissimum in reference streams had the average relative abundance of 20.3 ± 3.5%; the species Pseudostaurosira brevistriata and Staurosira construens var. venter in urban upstream had average relative abundances of 17.0% ± 0.9% and 17.3% ± 1.2%, respectively; and the species Nitzschia palea in urban downstream had average relative abundances of 18.8 ± 4.7%. There were significant correlations between the relative abundances of the dominant species and environmental variables, suggesting that the environmental variables had significant effects on the diatom distribution. Our results demonstrate that the diatom communities are relatively stable among seasons in different sampling areas, suggesting that diatoms can be used as reliable indicators for the biological monitoring of water quality in megacity streams across seasons.

Effects of urbanization on stream benthic invertebrate communities in Central Amazon

Accurate low flow measurements are important in groundwater-fed streams in order to assess in-stream flow requirements and the nature of stream interactions with groundwater, as well as the potential impacts of climate variability and climate change. Variability in stream discharge was measured over the low flow season in Bertrand Creek, Pepin Brook and Fishtrap Creek, which drain the Abbotsford-Sumas aquifer in southwest British Columbia and northwest Washington State. Discharge was measured to quantify variability: (1) along the length of the stream and relate those variations to differing groundwater contributions over the low flow season, and (2) across a series of cross-sections, both repeating across a middle cross-section (at-a-station measurements) and along consecutive sections from upstream to downstream (downstream measurements), to assess the repeatability of the low flow measurements. Downstream increases in discharge in Fishtrap Creek and Pepin Brook are attributed to groundwater discharging into the channels along these sections, as supported by lower dissolved oxygen concentrations and stable water temperatures. Along Bertrand Creek, stream water interaction with groundwater appears to be variable, with the stream recharging the aquifer along some reaches, and discharging in others. Over the summer season, discharge decreased in all streams; on average the decrease was in the range 0.01 to 0.05 m3/s. As the flow decreased, the coefficient of variation of the mean discharge tended to increase when the flow was very low (i.e., <0.1 m3/s), although the trends for Fishtrap were weak. Overall, the variations in measured discharge are of sufficient magnitude that subtle changes in streamflow caused by some real effect may be difficult to detect.

Summary Fluvial/deltaic deposits may be the most important hydrocarbon reservoirs in the world. Many large fields have reservoirs of varying combinations of braided-stream, point-bar, distributary-fill, and valley-fill deposits. Adeterministic relationship exists between natural phenomena and the nature of these deposits. Their location, size, shape, and internal porosity distribution are functions of stream processes. Reservoir geologists and engineers should use data that correlate related natural processes, stream variables, and fluvial facies to improve predictions in all aspects of reservoir description. predictions in all aspects of reservoir description. Introduction For a 1991 program to encourage production of 300 billion bbl of unrecovered oil, the U.S. DOE screened more than 2,000 U.S. oil fields and identified fluvial/deltaic reservoirs as the highest-priority targets. This is notsurprising. For 30 years, geoscientists have become increasingly aware of the importance of fluvial reservoir deposits. Since the advent of environmental facies analysis, studies have identified almost all major clastic reservoirs as fluvial or fluvial/deltaic in origin. If the immense quantities of heavy oil in fluvial/deltaic deposits of Venezuela and Canada are included, land-derived clastic reservoirs may surpass Middle East carbonate reservoirs in importance. Basic Assumptions. Sedimentologists and facies geologists have acknowledged the close relationship among depositional environments, the processes(physical, chemical, and biological) operating in them, and the facies (aspect)of the resulting deposits. It is generally accepted that deposition environment and processes are the primary factors influencing location, size, shape, and internal porosity distribution in many reservoirs, especially in land-derived elastic deposits. The most important characteristics of elastic reservoirs result from the combination of processes operating in a particular deposition environment. For fluvial/deltaic reservoirs, the tie between process and faciesis especially strong. The reliable causal relationships among gravity, flowing water, stream load, and reservoir deposits offer the promise of improved reservoir description. Domination of Fluvial/Deltaic Reservoirs. Most major hydrocarbon reservoirs are fluvial or fluvial/deltaic. Table 1 is a list of significant fluvial/deltaic fields that emphasizes the potential economic benefit that can result from the use of the potential economic benefit that can result from the use of the close process/facies relationship that molded their reservoirs. The list also calls attention to the circumstances and phenomena that concentrate and preserve large volumes of coarse, porous, and permeable debris in fluvial/deltaic reservoirs, and the reasons permeable debris in fluvial/deltaic reservoirs, and the reasons that tremendous volumes of hydrocarbons become concentrated in them. The close relationships among stream load, flow velocity, and stream gradient are important in molding fluvial/deltaic reservoirs. Whether reservoir-size elastic particles are transported or deposited is very sensitive to flow velocity. Fig. 1 clearly shows how water velocity determines whether a particle is deposited or transported. Stream velocity, although affected by discharge, nature of load, channel geometry, and texture of channel material, depends mostly on stream gradient. Stream and distributary gradients become very low in the lower alluvial valley and on coastal and deltaic plains. Coarse elastic particles are not readily transported under low-velocity conditions, so large amounts of reservoir material are deposited and eventually preserved in coastal- and deltaic-plain fluvial or fluvial/deltaic environments. The contribution of fluvial/deltaic deposits to major elastic sequences is important. Thick elastic deposits that fill a mega-sequence or thick wedge of stratigraphy must be composed of regressive prograding elasticdebris carried to the receiving basin by streams. With this premise, it is obvious that the terrigenous sediment usually would be introduced into the basin through fluvial-dominated deltas, where fluvial processes concentrate and preserve much of the coarse elastic debris in specific fluvial and closely associated environments. Fluvial Deposits Fluvial processes involve streams and stream deposits; however, many important factors affecting streams (gravity, gradient, discharge, load, and channel geometry) affect any unidirectional flow, including runoff from melting glaciers or density flows along deepwater channels. From high mountain valleys to deepwater fans, moving fluid can build levees, meander, branch, shift courses, and adjust channel geometry to discharge, all in response to the same causes. By understanding and using the influence of these natural processes on the behavior of streams and their facies, we can processes on the behavior of streams and their facies, we can improve reservoir description. JPT P. 368

Abstract. Agricultural watersheds are significant contributors to downstream nutrient excess issues. The timing and magnitude of nutrient mobilization in these watersheds are driven by a combination of anthropogenic, hydrologic, and biogeochemical factors that operate across a range of spatial and temporal scales. However, how, when, and where these complex factors drive nutrient mobilization has previously been difficult to capture with low-frequency or spatially limited data sets. To address this knowledge gap, we analyzed daily nitrate concentration (c) and discharge (Q) data for a 4-year period (2016–2019) from five nested, agricultural watersheds in the midwestern United States that contribute nutrient loads to the Gulf of Mexico. These records allow us to investigate nutrient mobilization patterns at a temporal and spatial resolution not previously possible. The watersheds span two distinct landforms shaped by differences in glacial history, resulting in natural soil properties that necessitated different drainage infrastructure across the study area. To investigate nutrient export patterns under different hydrologic conditions, we partitioned the hydrograph into stormflow and baseflow periods and examined those periods separately through the analysis of their concentration–discharge (c–Q) relationships on annual, seasonal, and event timescales. Stormflow showed consistent chemostatic patterns across all seasons, while baseflow showed seasonally dynamic c–Q patterns. Baseflow exhibited chemodynamic conditions in the summer and fall and more chemostatic conditions in the winter and spring, suggesting that water source contributions during baseflow were nonstationary. Baseflow chemodynamic behavior was driven by low-flow, low-NO3- conditions during which in-stream and near-stream biological processing likely moderated in-stream NO3- concentrations. Additionally, inputs from deeper groundwater with longer residence times and lower-NO3- concentration likely contributed to low-NO3- conditions in stream, particularly in the larger watersheds. Stormflow c–Q behavior was consistent across watersheds, but baseflow c–Q behavior was linked to the intensity of agriculture and the density of built drainage infrastructure, with more drainage infrastructure associated with higher loads and more chemostatic export patterns across the watersheds. This suggests that the way humans replumb the subsurface in response to geologic conditions has implications for hydrologic connectivity, homogenization of source areas, and, subsequently, nutrient export during both baseflow and stormflow. Our analysis also showed that anomalous flow periods greatly influenced overall c–Q patterns, suggesting that the analysis of high-resolution records at multiple scales is critical when interpreting seasonal or annual patterns.

In 2013, the U.S. Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) and USGS Columbia Environmental Research Center (CERC) will be collaborating with the U.S. Environmental Protection Agency (EPA) National Rivers and Streams Assessment (NRSA) to assess stream quality across the Midwestern United States. The sites selected for this study are a subset of the larger NRSA, implemented by the EPA, States and Tribes to sample flowing waters across the United States (http://water.epa.gov/type/rsl/monitoring/riverssurvey/index.cfm). The goals are to characterize water-quality stressors—contaminants, nutrients, and sediment—and ecological conditions in streams throughout the Midwest and to determine the relative effects of these stressors on aquatic organisms in the streams. Findings will contribute useful information for communities and policymakers by identifying which human and environmental factors are the most critical in controlling stream quality. This collaborative study enhances information provided to the public and policymakers and minimizes costs by leveraging and sharing data gathered under existing programs. In the spring and early summer, NAWQA will sample streams weekly for contaminants, nutrients, and sediment. During the same time period, CERC will test sediment and water samples for toxicity, deploy time-integrating samplers, and measure reproductive effects and biomarkers of contaminant exposure in fish or amphibians. NRSA will sample sites once during the summer to assess ecological and habitat conditions in the streams by collecting data on algal, macroinvertebrate, and fish communities and collecting detailed physical-habitat measurements. Study-team members from all three programs will work in collaboration with USGS Water Science Centers and State agencies on study design, execution of sampling and analysis, and reporting.

An integrative conservation planning framework for aquatic landscapes fragmented by road-stream crossings

Summary1. Recent research has addressed how transgenic residues from arable crops may influence adjacent waterways, aquatic consumers and important ecosystem processes such as litter breakdown rates. With future applications of transgenic plants in forestry, such concerns may apply to forest stream ecosystems. Before any large‐scale release of genetically modified (GM) trees, it is therefore imperative to evaluate the effects of genetic modifications in trees on such ecosystems.2. We conducted decomposition experiments under natural stream conditions using leaf litter from greenhouse grown GM trees (Populus tremula × Populus tremuloides) that express Bacillus thuringiensis (Bt) toxins (cry3Aa; targeting coleopteran leaf‐feeding beetles) to examine the hypothesis that GM trees would affect litter decomposition rates and/or the aquatic arthropod community that colonizes and feeds on leaf litter in streams.3. We show that two independent transformations of isogenic Populus trees to express Bt toxins caused similar changes to the composition of aquatic insects colonizing the leaf litter, ultimately manifested in a 25% and 33% increases in average insect abundance.4. Measurements of 24 phenolic compounds as well as nitrogen (N) and carbon (C) in the litter did not significantly differ among modified and wild‐type trees and were thus not sufficient to explain these differences in the insect assemblage.5. Decomposition rates were comparable among litter treatments suggesting that the normal suite of leaf traits influencing decomposition was similar among litter treatments and that the shredding functions of the community were maintained despite the changes in insect community composition.6. Synthesis and applications. We report that leaf litter from GM trees affected the composition of aquatic insect communities that colonized litter under natural stream conditions. This suggests that forest management using GM trees may affect adjacent waterways in unanticipated ways, which should be considered in future commercial applications of GM trees. We also argue that studies at different scales (e.g. species, communities and ecosystems) will be needed for a full understanding of the environmental effects of Bt plants.

We investigated the roles that velocity and substrate size play in the drift of stonefly larvae (Acroneuria abnormis). Acroneuria were introduced into an experimental flume containing homogeneous substrates of different size (small gravel, large gravel, or cobble), or a mixture of various substrate sizes. For each substrate Acroneuria were subjected to three different velocities (0.3, 0.6 and 0.9 ms−1) corresponding to base flow conditions in real streams, and the number of individuals entrained into the water column was measured. Entrainment was nearly two times higher from the smallest substrates than larger substrates and the heterogeneous mixture of substrate sizes. Higher entrainment from the small particles appeared to result from lower availability of refugia among particles and movement of particles under the higher water velocities. Entrainment generally increased with increasing discharge on small and large, but not intermediate-sized, particles. Our results suggest there may be dynamic Acroneuria entrainment under low flow conditions in streams.

Agricultural headwater streams in the Midwestern United States are subject to contaminants from fields, increased sedimentation, and degradation of natural habitat. Previous research has shown that physical instream habitat degradation better explained variation in fish community structure than water chemistry. However, these studies did not include total suspended solids (TSS), which are considered a major freshwater contaminant. The objective of this study is to determine whether total suspended solids better explains fish community structure than other variables in agricultural headwater streams. Mixed linear effects modeling was used to determine the set of independent variables that best predicts each of the fish response variables of species richness, Shannon diversity index, fish density, and index of biotic integrity. Standardized coefficients were used to determine which independent variable in each of the models had the largest influence on fish response metrics. The set of independent variables that best explained species richness were mean total suspended solids, imidacloprid, discharge, and substrate richness. Shannon diversity index was explained best by the combination of maximum total suspended solids, mean total suspended solids, atrazine, total nitrogen, and discharge. Fish density was explained best by the percentage of silt and clay, dissolved oxygen, the percentage of canopy cover, cover type richness, and discharge. IBI was explained best by the combination of the percentage of silt and clay, total phosphorus, mean total suspended solids, and dissolved oxygen. Total suspended solids was the most influential independent variable for fish species richness and Shannon diversity, however the percentage of silt and clay in benthic sediments was the most influential independent variable for fish density and IBI. Results also indicate discharge and total phosphorus as being influential to fish community metrics. The results from this study suggest that models containing a combination of different types of independent variables best explain fish community structure. This study supports the use of conservation and restoration practices that reduce total suspended solids and the amount of silt and clay present in bed sediments to increase fish community integrity of agricultural headwater streams of the Midwestern United States.

Baseline data from 1979 are presented on precipitation, streamflow, occurrence of permafrost, and physical and chemical water quality in a subarctic, tiaga watershed. First- to third-order streams drain catchments embracing permafrost-underlain and permafrost-free landscapes in the undisturbed research watershed. The data are compared to those from a fourth-order stream impacted by placer mining; streams in the research watershed drain into the fourth-order stream slightly beyond the watershed border. These and subsequent baseline data sets will be used to compare natural conditions in undisturbed streams of the subarctic to conditions in streams impacted by resource management activities and to evaluate the impacts of such activities on stream ecosystems.

The recent introduction of large geospatial databases and virtual measurement devices for streams of the United States have the potential to greatly improve stream classification systems as well as answer fundamental questions about river morphology. The physical condition of over 800 streams of the adjoining Upper Midwest and Temperate Plains ecoregions of the northcentral US were analyzed using principle components analysis of 10 selected site variables. Delineation was along three axes, with the first axis corresponding to differences in base flow, temperature, and soil permeability; the second corresponding to stream gradient, depth to bedrock and water table, and composite topographic index; and the third corresponding to stream sinuosity. Separation of streams into the two ecoregions was distinct, and primarily along axis 1. Adding a secondary matrix of 10 anthropogenic and geographic predictor variables produced a similar ecoregional separation, with latitude, percent of non-native plants, and overall intact habitat corresponding with axis 1. Natural and anthropogenic differences in streams of these two ecoregions appear inexorably linked, a situation probably common throughout the developed world.