Development and evaluation of predictive models for measuring the biological integrity of streams

The ratio of the number of observed taxa to that expected to occur in the absence of human-caused stress (OIE) is an intuitive and ecologically meaningful measure of biological integrity. We examined how OIE ratios derived from stream invertebrate data varied among 234 unimpaired reference sites and 254 test sites potentially impaired by past logging. Data were collected from streams in three montane ecoregions in California. Two sets of River Invertebrate Prediction and Classification System (RIVPACS) predictive models were built: one set of models was based on near-species taxonomic resolution; the other was based on family identifications. Two models were built for each level of taxonomic resolution: one calculated 0 and E based on all taxa with probabilities of capture (PC) \u3e 0; the other calculated 0 and E based on only those taxa with PC2 0.5. Evaluations of the performance of each model were based on three criteria: (1) how well models predicted the taxa found at unimpaired sites, (2) the degree to which OIE values differed among unimpaired reference sites and potentially impaired test sites, and (3) the degree to which test site OIE values were correlated with independent measures of watershed alteration. Predictions of species models were more accurate than those of family models, and predictions of the PC2 0.5 species model were more robust than predictions of the PC2 0 model. OIE values derived from both species models were related to land use variables, but only assessments based on the PC2 0.5 model were insensitive to naturally occurring differences among streams, ecoregions, and year

NADPH Oxidase Limits Innate Immune Responses in the Lungs in Mice

Background: Chronic granulomatous disease (CGD), an inherited disorder of the NADPH oxidase in which phagocytes are defective in generating superoxide anion and downstream reactive oxidant intermediates (ROIs), is characterized by recurrent bacterial and fungal infections and by excessive inflammation (e.g., inflammatory bowel disease). The mechanisms by which NADPH oxidase regulates inflammation are not well understood. Methodology/Principal Findings: We found that NADPH oxidase restrains inflammation by modulating redox-sensitive innate immune pathways. When challenged with either intratracheal zymosan or LPS, NADPH oxidase-deficient p47phox-/- mice and gp91phox-deficient mice developed exaggerated and progressive lung inflammation, augmented NF-kB activation, and elevated downstream pro-inflammatory cytokines (TNF-α, IL-17, and G-CSF) compared to wildtype mice. Replacement of functional NADPH oxidase in bone marrow-derived cells restored the normal lung inflammatory response. Studies in vivo and in isolated macrophages demonstrated that in the absence of functional NADPH oxidase, zymosan failed to activate Nrf2, a key redox-sensitive anti-inflammatory regulator. The triterpenoid, CDDO-Im, activated Nrf2 independently of NADPH oxidase and reduced zymosan-induced lung inflammation in CGD mice. Consistent with these findings, zymosan-treated peripheral blood mononuclear cells from X-linked CGD patients showed impaired Nrf2 activity and increased NF-kB activation. Conclusions/Significance: These studies support a model in which NADPH oxidase-dependent, redox-mediated signaling is critical for termination of lung inflammation and suggest new potential therapeutic targets for CGD

Comparing Effects of Nutrients on Algal Biomass in Streams in Two Regions with Different Disturbance Regimes and with Applications for Developing Nutrient Criteria

Responses of stream algal biomass to nutrient enrichment were studied in two regions where differences in hydrologic variability cause great differences in herbivory. Around northwestern Kentucky (KY) hydrologic variability constrains invertebrate biomass and their effects on algae, but hydrologic stability in Michigan (MI) streams permits accrual of high herbivore densities and herbivory of benthic algae. Multiple indicators of algal biomass and nutrient availability were measured in 104 streams with repeated sampling at each site over a 2−month period. Many measures of algal biomass and nutrient availability were positively correlated in both regions, however the amount of variation explained varied with measures of biomass and nutrient concentration and with region. Indicators of diatom biomass were higher in KY than MI, but were not related to nutrient concentrations in either region. Chl   a and % area of substratum covered by Cladophora were positively correlated to nutrient concentrations in both regions. Cladophora responded significantly more to nutrients in MI than KY. Total phosphorus (TP) and total nitrogen (TN) explained similar amounts of variation in algal biomass, and not significantly more variation in biomass than dissolved nutrient concentrations. Low N:P ratios in the benthic algae indicated N as well as P may be limiting their accrual. Most observed responses in benthic algal biomass occurred in nutrient concentrations between 10 and 30 μg TP  l −1 and between 400 and 1000 μg TN l −1 .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42905/1/10750_2005_Article_1611.pd

Hydrologic Variability Affects Invertebrate Grazing on Phototrophic Biofilms in Stream Microcosms

The temporal variability of streamflow is known to be a key feature structuring and controlling fluvial ecological communities and ecosystem processes. Although alterations of streamflow regime due to habitat fragmentation or other anthropogenic factors are ubiquitous, a quantitative understanding of their implications on ecosystem structure and function is far from complete. Here, by experimenting with two contrasting flow regimes in stream microcosms, we provide a novel mechanistic explanation for how fluctuating flow regimes may affect grazing of phototrophic biofilms (i.e., periphyton) by an invertebrate species (Ecdyonurus sp.). In both flow regimes light availability was manipulated as a control on autotroph biofilm productivity and grazer activity, thereby allowing the test of flow regime effects across various ratios of biofilm biomass to grazing activity. Average grazing rates were significantly enhanced under variable flow conditions and this effect was highest at intermediate light availability. Our results suggest that stochastic flow regimes, characterised by suitable fluctuations and temporal persistence, may offer increased windows of opportunity for grazing under favourable shear stress conditions. This bears important implications for the development of comprehensive schemes for water resources management and for the understanding of trophic carbon transfer in stream food webs

Tailed frog tadpoles differentially alter their feeding behavior in response to non-visual cues from four predators

Tadpoles of the tailed frog (Ascaphus truei) are common in riffles within many small, high-gradient streams of the Pacific Northwest (United States and southern Canada), where they typically graze periphyton from exposed cobbles. We conducted field observations and experiments in Clearwater Creek, southwestern Washington, to determine if tadpoles would reduce their feeding activity (i.e., emergence from crevices to graze periphyton) in the presence of non-visual cues released from each of four aquatic predators: giant salamanders (Dicamptodon spp.), cutthroat trout (Salmo clarki), brook trout (Salvelinus fontinalis), and shorthead sculpin (Cottus confusus). In absence of predators, tadpoles usually emerged from under cobbles to feed at night (2000-0100 h), and spent the remainder of the 24-h interval hidden in crevices. In the presence of giant salamanders, cutthroat trout, and brook trout that were all confined within separate, in situ enclosures immediately upstream of tadpoles, tadpole activity was reduced two-, three-, and six-fold, respectively, compared with predator-free controls. In contrast, tadpoles appeared unable to detect upstream sculpins. Subsequent consumption experiments in the laboratory showed that salamanders, sculpins, and cutthroat trout all were capable of consuming tadpoles in both structurally simple and complex habitats. We hypothesize that the inability of tadpoles to detect predaceous sculpins may explain why tailed frog tadpoles are largely absent from lower-gradient streams where sculpins are often abunda

Interactions between stream herbivores and periphyton: a quantitative analysis of past experiments

This review summarizes the state of knowledge regarding herbivory in stream ecosystems by quantitatively analyzing the results of 89 experimental studies published between 1972 and 1993. Our primary objective was to determine if general patterns exist among stream ecosystems in the type and strength of interactions occurring between herbivores (grazers) and their primary food source, periphyton. We conducted two types of meta-analyses of the published literature: (1) analyses of the proportion of studies showing significant effects for three types of interactions (effects of grazers on periphyton, effects of periphyton on grazers, and effects of grazers on other grazers and benthic animals) and (2) analyses of factors influencing the magnitude of effect that grazers had on periphyton. For effects of grazers on periphyton, we also determined (1) if the likelihood of observing significant effects varied with the spatial and temporal scale at which experiments were done and (2) if the magnitude of effect by grazers on periphyton abundance varied with spatial and temporal scale, grazer taxon, grazer abundance, and periphyton accrual based on the difference in treatments with and without grazers. Grazers held at ambient densities usually reduced periphyton biomass (70% of experiments) and altered algal taxonomic or physiognomic structure (81%) relative to grazer removal treatments, whereas grazers had slightly lower effects on periphyton productivity (usually \u3c70% of experiments, depending on productivity measure). Experiments conducted in laboratory streams and at two spatial scales in the field (few or single habitat units and stream reaches or basins) were equally likely to report significant effects of grazers. Both short-term (≤4 wk) and longterm (\u3e4 wk) experiments also were equally likely to report significant effects of grazers on periphyton. However, the magnitude of effect grazers had on periphyton biomass varied with the amount of periphyton accrual, grazer taxon, and grazer population biomass. Grazer effects also were higher for longer studies conducted under laboratory conditions than for shorter studies conducted in the field. A high proportion of the experiments that manipulated periphyton abundance significantly affected grazer densities and growth. Reduction in periphyton abundance usually reduced grazer density and growth. Experimental manipulations of dominant grazers typically had strong and usually negative effects on densities and growth of other species of benthic animals, either from direct (e.g., interference) or indirect (e.g., resource exploitation) mechanisms. Results of these analyses suggest that stream herbivores regulate their food resources as or more frequently than herbivores in other ecosystems, and strongly contradict the view held by many ecologists that stream communities are regulated primarily by abiotic factors. Although publication bias (i.e., the tendency for journals to publish positive results) appears minimal, we cannot yet generalize from these results to the entire universe of stream ecosystems because (1) most studies were conducted during summer base flow conditions and (2) results do not adequately represent interactions during the more physically stressful conditions that occur during periods of flooding, drought, or extreme cold. If rapid progress in the development of general stream ecosystem theory is to occur, we believe (1) future studies should be explicitly designed within the context of general ecological questions, (2) as much background information as possible describing environmental conditions should be collected, and (3) journals should permit and urge inclusion of tabular data describing both experimental conditions and treatment means and variances. Interactions between Stream Herbivores and Periphyton: A Quantitative Analysis of past Experiments - ResearchGate. Available from: http://www.researchgate.net/publication/272542810_Interactions_between_Stream_Herbivores_and_Periphyton_A_Quantitative_Analysis_of_past_Experiments [accessed Jul 10, 2015]

Channel morphology, water temperature, and assemblage structure of stream insects

Temperature is known to be an important mechanism affecting the growth and distribution of stream insects. However, little information exists that describes how variable temperatures are among streams of similar size, especially in physically heterogeneous landscapes. We measured summer daytime temperature and the structure of riffle benthic insect assemblages from 45 montane streams in California. Summer stream temperature was nearly randomly distributed across large-scale geographic gradients of latitude (6?) and elevation (2000 m). The lack of geographic trends in summertime stream temperature appeared to be caused by the strong relationship between local channel morphology and summer water temperature. Mean daytime water temperature was most strongly related to the % of the channel present as pools, which did not vary systematically with either latitude or elevation. We used multiple multivariate regression analysis, non-metric multidimensional scaling (NMDS), and graphical techniques to both quantify differences in insect assemblage structure among streams and to determine the degree to which assemblage structure was related to temperature. NMDS analyses were conducted on 3 similarity matrices based on: 1) presence and absence of all aquatic insect taxa encountered during the study, 2) densities of the 16 most numerically abundant taxa, and 3) population biomasses of the 16 most common taxa. All 3 analyses showed that variation in assemblage structure among streams was significantly related to temperature, although assemblage structure was most strongly related to sampling date-a consequence of sampling over a 98-d period. Temperature probably influenced assemblage structure in 2 ways: 1) by influencing developmental rates of individual taxa and overall assemblage phenology, thus affecting the relative abundances of taxa found on a specific sampling date, and 2) by excluding taxa unable to tolerate certain temperature ranges. Because of the strong dependency of assemblage structure on temperature and the lack of strong geographic trends in temperature among these streams, much of the measured variation in assemblage structure appeared to be unrelated to latitude or elevation. These results have important implications for both our understanding of natural biogeographic patterns of lotic organisms and our ability to detect and model the effects of climate change and other thermal alterations on stream ecosystems

Associations between small dams and mollusk assemblages in Alabama streams

Small dams are ubiquitous yet poorly understood features in many streams. Dam removal is being used increasingly in stream restoration projects as a means to enhance habitat connectivity and ecosystem function. However, habitat- and assemblage-level effects of small dams on stream mollusk assemblages are poorly documented. We examined associations between stream physico chemical habitat variables and mollusk assemblages at 22 small (\u3c10 m) dams in 3rd–5th order Alabama streams. We sampled 66 reaches (3 reaches/dam) associated with intact, breached, and relict small dams. For each dam, we designated 3 study reaches: 1) immediately downstream from the dam, 2) 500 to 5000 m downstream, and 3) 500 to 5000 m upstream from the impounded or formerly impounded zone. We used principal components analysis (PCA) to examine variation in physical-habitat conditions across all sites. Four principal components accounted for 72% of the variation in physical-habitat conditions across sites. One PC score (PC1, corresponding to increased substrate size) was negatively associated with several mollusk metrics including total mussel abundance, taxon richness, catch-per-unit-effort (CPUE), and density. We observed few significant differences between simple habitat variables at sites up- and downstream of dams. However, streams with intact dams had significantly higher mussel catch rates (CPUE) and taxon richness than did streams with breached or relict dams.We used forward-stepwise multiple regression to model the effects of habitat variables (as standardized PC scores) on mollusk assemblage metrics. PCs representing substrate composition were the strongest predictors of total mussel abundance and richness. Abundance of other mollusks including deposit-feeding snails, the exotic bivalve Corbicula fluminea, and fingernail clams was correlated with PC scores describing variability in substrate organic matter composition or stream gradient. We think these data indicate that some intact dams enhance mollusk habitat in downstream reaches. Streams with intact dams appear to be more geomorphically stable than streams with breached or relict dams and conditions in the mill reach may reflect pre construction stream conditions. Breached dams warrant higher prioritization for removal than intact structures because habitat degradation may persist for decades and impede re-establishment of native mollusk populations