How freshwater biomonitoring tools vary sub‐seasonally reflects temporary river flow regimes

Characterizing temporary river ecosystem responses to flow regimes is vital for conserving their biodiversity and the services they provide to society. However, freshwater biomonitoring tools rarely reflect community responses to hydrological variations or flow cessation events, and those available have not been widely tested within temporary rivers. This study examines two invertebrate biomonitoring tools characterizing community responses to different flow‐related properties: the “Drought Effect of Habitat Loss on Invertebrates” (DEHLI) and “Lotic‐invertebrate Index for Flow Evaluation” (LIFE), which, respectively reflect community responses to habitat and hydraulic properties associated with changing flow conditions. Sub‐seasonal (monthly) variations of LIFE and DEHLI were explored within two groundwater‐fed intermittent rivers, one dries sporadically (a flashy, karstic hydrology—River Lathkill) and the other dries seasonally (a highly buffered flow regime—South Winterbourne). Biomonitoring tools were highly sensitive to channel drying and also responded to reduced discharges in permanently flowing reaches. Biomonitoring tools captured ecological recovery patterns in the Lathkill following a supra‐seasonal drought. Some unexpected results were observed in the South Winterbourne where LIFE and DEHLI indicated relatively high‐flow conditions despite low discharges occurring during some summer months. This probably reflected macrophyte encroachment, which benefitted certain invertebrates (e.g., marginal‐dwelling taxa) and highlights the importance of considering instream habitat conditions when interpreting flow regime influences on biomonitoring tools. Although LIFE and DEHLI were positively correlated, the latter responded more clearly to drying events, highlighting that communities respond strongly to the disconnection of instream habitats as flows recede. The results highlighted short‐term ecological responses to hydrological variations and the value in adopting sub‐seasonal sampling strategies within temporary rivers. Findings from this study indicate the importance of establishing flow response guilds which group taxa that respond comparably to flow cessation events. Such information could be adopted within biomonitoring practices to better characterize temporary river ecosystem responses to hydrological variations.     

Macroinvertebrate Community Responses to Annual Flow Variation from River Regulation: An 11‐Year Study

The majority of the world's large river systems is affected by dams. The influences of unnatural regimes induced by flow management are wide‐ranging from both biotic and abiotic standpoints. However, many of these effects are not evident over short (1–2 years) periods (e.g. impacts of annual flow variation). This study examines the long‐term effects of annual flow variation on the macroinvertebrate community in the Chattahoochee River (GA) in the reaches below Buford Dam, the major water control structure on the river. Quarterly, macroinvertebrate samples were taken from 2001 to 2011 using Surber and Hester–Dendy plate samplers at six locations spread across 65 km below the dam. Data were analysed via analysis of similarities to determine differences in community composition between high‐flow (mean discharge = 58.27 m³/s) and low‐flow (mean discharge = 26.53 m³/s) years. Taxa that contributed most to community differences were determined via similarity percentages analyses and subsequent t‐tests. Several insect taxa (e.g. Cheumatopsyche and Ceratopsyche caddisfly larvae, Maccaffertium mayfly nymphs and Taeniopteryx stonefly nymphs) were more prevalent under the high‐flow regime. Non‐insect macroinvertebrates (e.g. Crangonyx amphipods, Tricladida flatworms and Caecidotea isopods) were more abundant under low‐flow conditions. In terms of taxon richness, no significant effects of flow regime were detected. Implications of macroinvertebrate patterns for the fishery and ecological health of the river are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

SHORT‐TERM IMPACTS OF LATERAL HYDROLOGICAL CONNECTIVITY RESTORATION ON AQUATIC MACROINVERTEBRATES

In floodplain ecosystems, the lateral hydrological connectivity between the main river channel and the secondary channels plays a major role in shaping both the habitat conditions and the macroinvertebrate diversity. Among other threats, human activities tend to reduce the lateral connectivity, which increases floodplain terrestrialization and induces a loss of aquatic biodiversity. Consequently, the restoration of lateral connectivity is of growing concern. We studied four secondary channels of the Rhône floodplain that were subjected either to no restoration or to three different restoration measures (river flow increase only, flow increase plus dredging and flow increase plus reconnection to the river). Macroinvertebrate and environmental data were analysed one year before and during a period of five years after restoration. We expected a progressive increase of lateral connectivity according to the type of restoration. Changes in macroinvertebrate assemblages were predicted to be towards more rheophilic communities and proportionally related to the changes in lateral connectivity. In the reconnected channel, lateral connectivity increased and remained high five years after restoration. In the dredged channel, the immediate increase of the lateral connectivity metric induced by sediment removal was followed by a rapid decrease. In the unrestored channel and the channel only influenced by flow increase, the metric remained constant in time. The macroinvertebrate composition and the rarefied EPT richness changes were proportionally related to the changes in lateral connectivity. Alien species richness and densities increased progressively in all channels after restoration. Our results showed that modifications of the lateral connectivity lead to predictable changes in macroinvertebrate diversity. Synergistic interactions between restoration and longer‐term changes (e.g. climatic change, invasion of alien species) encourage long‐term monitoring to assess the durability and trends of restoration measures. Copyright © 2012 John Wiley & Sons, Ltd.     

Spatial patterns of fish communities in the Upper Mississippi River System: assessing fragmentation by low‐head dams

We assessed the similarity of fish communities among river reaches to assess community‐level fragmentation by low‐head dams in the Upper Mississippi River System (UMRS). The spatial coverage of standardized electrofishing sampling used in the Long Term Resource Monitoring Program (LTRMP) was extended for three of the six regional trend areas (RTA; pools 4, 13, and the Open River Reach) to include river reaches (outpools) immediately upstream and downstream from the standard RTA from 15 June to 31 October 2000. Additionally, pools 19 and 20 were sampled in September 2000. Cluster analysis and non‐metric multidimensional scaling of community composition and structure data revealed two major groups, upper and lower reaches, and four (for composition) or five (for structure) sub‐groupings of river reaches. In general, all outpools grouped with the nearest RTA for both community composition (no exception) and community structure (one exception). This suggests that fragmentation of fish communities from low‐head dams is minimal. Mantel correlations demonstrated strong inverse association between the similarity of fish communities with the distance between reaches. Habitat variables measured during electrofishing collections were significantly correlated with spatial variation of fish composition and community structure, but provided only marginal improvements to correlations with distance between reaches alone. Furthermore, habitat variability among river reaches also was related to distance between reaches. Determining the extent to which variation of fish communities is related to habitat or demographic processes (e.g. migration, larval drift, source‐sink dynamics) will be challenging for this system. Although low‐head dams on the UMRS may restrict movements for individuals and populations of certain fish species, we found little evidence that these effects have led to substantial, community‐level fragmentation. Copyright © 2006 John Wiley & Sons, Ltd.     

Using Benthic Indicator Species and Community Gradients to Optimize Restoration in the Arid,Endorheic Walker River Watershed,Western USA

The challenge of restoring watersheds in arid regions often requires the development of novel scientific tools to guide management. The Walker Basin Program was created to reverse ecological decline in an arid, endorheic watershed through scientifically guided restoration. As part of this programme, 3 years of benthic macroinvertebrate samples were collected seasonally at 10 sites that represent the diversity of river environments from the high‐mountain headwaters to a desert terminal lake. Samples were analysed to quantify baseline conditions in reference and degraded reaches of river and identify opportunities and constraints for aquatic community restoration. Naturally harsh environments in the lower river characterized by high temperatures and low base flow combined with a weak understanding of reference conditions to limit the utility of commonly used indices for quantifying biotic integrity. A flexible approach was employed using a combination of indicator species analysis, cluster analysis, canonical correspondence analysis, and community tolerance indices to evaluate the variation of benthic macroinvertebrate community composition across a set of environmental gradients. Results demonstrate that benthic communities in the watershed are primarily influenced by a longitudinal gradient related to elevation. A strong secondary community gradient caused by anthropogenic nutrient loading may constrain restoration effectiveness in some parts of the watershed. Restoration activities should improve water quality conditions and initially target areas of the watershed less affected by nutrient loading. Results also demonstrate that benthic communities shift longitudinally. These shifts should be monitored to inform adaptive management of restoration actions. Copyright © 2014 John Wiley & Sons, Ltd.     

Multiple lines of evidence for the beneficial effects of environmental flows in two lowland rivers in Victoria,Australia

The aim of this study was to identify whether environmental flows released into two lowland rivers (the Glenelg and Wimmera Rivers, western Victoria, Australia) during the spring to autumn period had successfully ameliorated the negative effects of multiple human impacts. Macroinvertebrates and a range of physico‐chemical variables were sampled from three reaches in each river. Both rivers were sampled during three environmental release seasons with average‐sized releases (1997–1998, 1998–1999 and 2001–2002) and two drought seasons with limited releases (1999–2000 and 2000–2001). The effects of releasing average‐sized environmental flows on macroinvertebrates and physico‐chemical variables were assessed by comparison with data from the two drought seasons. For the Glenelg River, data from a reference season prior to the release of environmental flows (1995–1996) was also compared to data from the five environmental flow seasons. Multivariate analyses revealed four pieces of evidence indicating that the release of environmental flows effectively slowed the process of environmental degradation in the Glenelg River but not in the Wimmera River: (1) the magnitude of the river discharge was dependent on the size of environmental flow releases; (2) in the Wimmera River, water quality deteriorated markedly during the two drought seasons and correlated strongly with macroinvertebrate assemblage structure, but this was not observed in the Glenelg River; (3) the taxonomic composition of the macroinvertebrate assemblages among contrasting flow release seasons reflected the severe deterioration in water quality of the Wimmera River; (4) despite two drought seasons with minimal environmental flow releases, the macroinvertebrate assemblage in the Glenelg River did not differ from the average‐release seasons, nor did it return to a pre‐environmental flows condition. Therefore, it appears that environmental flow releases did sustain the macroinvertebrate assemblage and maintain reasonable water quality in the Glenelg River. However, in the Wimmera River, release volumes were too small to maintain low salinities and were associated with marked changes in the macroinvertebrate assemblage. Therefore, there are multiple lines of evidence that environmental flow releases of sufficient magnitude may slow the process of degradation in a regulated lowland river. Copyright © 2007 John Wiley & Sons, Ltd.     

Longitudinal changes in macroinvertebrate assemblages in the Meuse River: anthropogenic effects versus natural change

A collaborative study among three nations (France, Belgium, Netherlands) along the Meuse River developed a consistent approach for collecting and interpreting macroinvertebrate data. Specific mesohabitats were sampled in 16 locations along an 800‐km stretch of this lowland regulated river. The objective was to assess the ‘river health’ using macroinvertebrate communities as indicators of biological and ecological variation in space. The main changes in assemblages were investigated using multimetric and multivariate approaches. The authors examined relationships between faunal variations and both physico‐chemical gradients and man‐made disturbances. We related species traits to faunal changes and habitat characteristics. Both a gradual shift from a macroinvertebrate assemblage dominated by insects to a community dominated by crustaceans and molluscs and a drastic decrease in biotic index values were observed along the longitudinal gradient. Taxa were distributed according to oxygen, nitrate and ammonium concentrations, pH, conductivity and summer hydraulic conditions. But major faunal differences among sites could not be explained simply by physico‐chemical variables. The trait analysis underlined the role of temporary habitats in structuring the summer macroinvertebrate community of sites of the uppermost French sector, which supported the most diverse community in terms of trait combination. Downstream the macroinvertebrate community exhibited a more simple and less stable functional organization. We concluded that the Meuse River exhibited both a high biodiversity and a ‘reasonably good’ water quality in the upper reaches. Two transition zones highlighted the influence of a high degree of human impact on stream integrity. Regulation for navigation, ship traffic and heavily polluted effluent discharges influenced instream conditions via multiple processes determining a decline of both habitat stability and diversity. However, the rare occurrence of habitat‐sensitive species in the lower reaches indicated that a partial recovery of communities may be predicted if restoration and protection of disturbed (especially riparian) habitats are fulfilled. Copyright © 2002 John Wiley & Sons, Ltd.     

Assessing the effects of hydrological and chemical stressors on macroinvertebrate community in an Alpine river: The Adige River as a case study

In this study, the combined effects of hydrological and chemical stressors on benthic macroinvertebrates were evaluated in order to explore the response of the biological community to multiple stressors. The Adige River, located in the south‐eastern Alps, was selected as a case study because representative of the situation of a large river in which the variety of stressors present in the Alpine region act simultaneously. As expected, streamflow showed a seasonal pattern, with high flows in the spring–summer period; however, locally, the natural hydrological regime was altered by the presence of hydropower systems, which chiefly affected low flows. Multivariate analysis showed seasonal and spatial patterns in both chemical and hydrological parameters with a clear gradient in the concentration of nitrate, personal care, and pharmaceutical products moving from headwaters to the main stem of the river. The macroinvertebrate community composition was significantly different in summer and winter and between up and downstream sites. Streamflow alteration chiefly due to water use by hydropower affected community composition but not richness or diversity. Gammarus sp., Hirudinea, and Psychomyia sp., were positively correlated with flow variability, increasing their densities in the sites with higher streamflow variability because of hydropeaking. The results obtained in this study show that the composition of the macroinvertebrate community responded to seasonality and to changes in the main stressors along the river and highlights the importance of the spatial and temporal variability of stressors in this Alpine river. Taking into account, this variability will help the decision‐making process for improving basin management.     

River flow indexing using British benthic macroinvertebrates: a framework for setting hydroecological objectives

A method linking qualitative and semi‐quantitative change in riverine benthic macroinvertebrate communities to prevailing flow regimes is proposed. The Lotic‐invertebrate Index for Flow Evaluation (LIFE) technique is based on data derived from established survey methods, that incorporate sampling strategies considered highly appropriate for assessing the impact of variable flows on benthic populations. Hydroecological links have been investigated in a number of English rivers, after correlating LIFE scores obtained over a number of years with several hundred different flow variables. This process identifies the most significant relationships between flow and LIFE which, in turn, enables those features of flow that are of critical importance in influencing community structure in different rivers to be defined. Summer flow variables are thus highlighted as being most influential in predicting community structure in most chalk and limestone streams, whereas invertebrate communities colonizing rivers draining impermeable catchments are much more influenced by short‐term hydrological events. Biota present in rivers with regulated or augmented flows tend to be most strongly affected by non‐seasonal, interannual flow variation. These responses provide opportunities for analysing and elucidating hydroecological relationships in some detail, and it should ultimately be possible to use these data to set highly relevant, cost‐effective hydroecological objectives. An example is presented to show how this might be accomplished. Key areas of further work include the need to provide robust procedures for setting hydroecological objectives, investigation of habitat quality and LIFE score relationships in natural and degraded river reaches and evaluation of potential links with other biological modelling methods such as RIVPACS. Copyright © 1999 John Wiley & Sons, Ltd.     

Cascade macroinvertebrate assemblages for in‐stream flow criteria and biomonitoring of tropical mountain streams

Few comprehensive studies on stream assessment and biomonitoring have been conducted in tropical, freshwater watersheds. Currently under threat from climate change, urbanization and increasing freshwater demands, there is a need for innovative approaches to tropical watershed assessment and management. This study investigated cascade habitat macroinvertebrate communities among four tropical mountain streams with the goal of enhancing future efforts to identify flow biocriteria for watersheds of Polynesia. Cascade macroinvertebrate communities were compared between streams of differing size and magnitude of flow removal to evaluate the biological effects of water withdrawal on benthic communities. Two cascade microhabitats, identified as torrenticolous and amphibious, were evaluated for macroinvertebrate community differences and presence of native taxa among watersheds. Cascade habitat in general was reduced, by as much as 98%, in downstream reaches, having a significant impact on the stream ecosystem physical template important for native stream communities. In addition, two‐way ANOVA results revealed no main effects, but significant interactions of watershed size and flow removal on mean macroinvertebrate density for torrenticolous microhabitats; however, the opposite was true for the amphibious microhabitat. Diversity was significantly higher under undiverted flow conditions (t = 4.21, df = 272, p = 0.0004) and in torrenticolous microhabitats (t = 3.86, df = 272, p < 0.0001) over the entire study period. The amphibious microhabitat was composed of 39% native taxa, while the torrenticolous microhabitat contained <7%. This study provides new options for biomonitoring of native populations in Polynesian watersheds. Further studies that support the development of in‐stream flow criteria to preserve cascades are important to understanding the role of this habitat in tropical stream ecosystem function. Copyright © 2010 John Wiley & Sons, Ltd.     

Microinvertebrate dynamics in riverine slackwater and mid‐channel habitats in relation to physico‐chemical parameters and food availability

Microinvertebrates play a critical role in riverine food webs, and recent studies have hypothesized that slackwaters, non‐flowing regions associated with the main channel, are important for their reproduction and recruitment. However, little is known regarding the population and community dynamics of microinvertebrate communities in slackwater regions, or how they compare with those in mid‐channel regions. This study examined microinvertebrate communities in the epibenthic and pelagic zones of slackwater and mid‐channel regions (i.e. four habitats) of an Australian floodplain river in relation to physico‐chemical parameters and food availability (as estimated by chlorophyll‐a concentration) between September 2005 and November 2006. Results from this study indicate that microinvertebrate abundance and diversity were greater in slackwater habitats than mid‐channel habitats overall, corresponding with the slower current velocities associated with the former. Nevertheless, communities in all four habitats were most abundant and diverse in late spring (coinciding with an increase in water temperature), and followed similar seasonal trajectories in terms of density, taxon richness and community structure. These findings support the view that slackwaters are important for in‐channel microinvertebrate production, and suggest that animals frequently disperse (either actively or passively) among slackwater and other main channel regions year round. Given the critical importance of microinvertebrates in riverine food webs, rivers should be managed with a view to maintaining a natural variety of accessible slackwater regions in order to support the production and survival of microinvertebrate communities. Copyright © 2009 John Wiley & Sons, Ltd.     

MACROINVERTEBRATE COMMUNITY CONDITION ASSOCIATED WITH THE SEVERITY OF STREAMFLOW ALTERATION

Natural streamflows play a critical role in stream ecosystems, yet quantitative relations between streamflow alteration and stream health have been elusive. One reason for this difficulty is that neither streamflow alteration nor ecological responses are measured relative to their natural expectations. We assessed macroinvertebrate community condition in 25 mountain streams representing a large gradient of streamflow alteration, which we quantified as the departure of observed flows from natural expectations. Observed flows were obtained from US Geological Survey streamgaging stations and discharge records from dams and diversion structures. During low‐flow conditions in September, samples of macroinvertebrate communities were collected at each site, in addition to measures of physical habitat, water chemistry and organic matter. In general, streamflows were artificially high during summer and artificially low throughout the rest of the year. Biological condition, as measured by richness of sensitive taxa (Ephemeroptera, Plecoptera and Trichoptera) and taxonomic completeness (O/E), was strongly and negatively related to the severity of depleted flows in winter. Analyses of macroinvertebrate traits suggest that taxa losses may have been caused by thermal modification associated with streamflow alteration. Our study yielded quantitative relations between the severity of streamflow alteration and the degree of biological impairment and suggests that water management that reduces streamflows during winter months is likely to have negative effects on downstream benthic communities in Utah mountain streams. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

AN EXAMINATION OF THE IMPACT OF MULTIPLE DISTURBANCES ON A RIVER SYSTEM: TAXONOMIC METRICS VERSUS BIOLOGICAL TRAITS

River reaches are often subject to multiple co‐occurring anthropogenic stressors. Disentangling the relative impacts of different stressors is important in developing river management strategies. Bio‐assessments using taxonomically based metrics (e.g. taxa richness and diversity) are frequently used as a means of determining the impact of stressors on river reach quality. Although this method has been successful in determining river reach quality, taxonomically based metrics are often limited in their ability to distinguish mechanisms of impact and thus the importance of different stressors. In contrast, biological traits can provide a mechanistic understanding of anthropogenic stressor impacts and therefore have the potential to identify the importance of different co‐occurring stressors. Using both taxonomically based metrics and biological traits, we examined the impact of two common co‐occurring stressors, summer water withdrawal and channelization, on the macroinvertebrate assemblage of a Columbia River tributary Both metrics and traits showed a strong shift at the point where intense channelization began. However, the metrics failed to distinguish whether channelization or co‐occurring water withdrawal was the driver of change. In contrast, biological traits indicated that the assemblage within the heavily channelized area shifted to one dominated by resilience traits often found in river reaches subject to scouring flows. This result indicates that scouring flows associated with intense channelization are the primary driver of change in the macroinvertebrate assemblage and that water withdrawals had little observable impact. Our results demonstrate the utility of biological traits for disentangling the impact of multiple stressors in river systems. Copyright © 2011 John Wiley & Sons, Ltd.     

The effect of damming on biological quality according to macroinvertebrates in some Estonian streams,Central—Baltic Europe: A pilot study

The effect of damming on the structure of the macroinvertebrate community and biological quality was studied in nine (the 3–6th order) lowland streams of Estonia, Central—Baltic ecoregion of Europe. Four habitats—reservoirs with accumulated fine sediments, reservoirs with hard bottom, and two corresponding below‐dam areas (both fast‐flowing)—were compared to study whether and how significantly the bottom substrata in dammed areas affected macroinvertebrates and biological quality downstream of dams. The standard kick‐net samples (1.25 m², complemented with qualitative sample) were collected in autumn 2005—spring 2006. The multimetric biological quality, based on five macroinvertebrate indices (total taxa richness, EPT taxa richness, Average Score Per Taxon, Danish Stream Fauna Index, Shannon diversity) was estimated and compared with reference values. Biological quality in reservoirs with hard bottom and their downstream reaches corresponded to good, or even high quality. Conversely, damming affected biological quality significantly and negatively, above the dam if fine sediments were accumulated. The effect was the strongest within muddy reservoirs themselves (revealing moderate quality only). However, some harmful consequences of mud were observed also downstream of dams. The results also demonstrated that the indices of estimation of organic pollution and/or general quality were able to reflect significant changes in stream flow. Copyright © 2010 John Wiley & Sons, Ltd.     

Plant dispersal along rivers fragmented by dams

To understand the influence of dams on connectivity of riparian plant communities along rivers, we examined plant dispersal by water (hydrochory) and riparian plant community attributes upstream and downstream from dams on two rivers in the southern Rocky Mountains, Colorado, USA. Drifting plant propagules were collected from the water column along reaches upstream and downstream from dams to examine the longitudinal and temporal variation in seed‐pool species composition and concentration of water‐transported seeds. Similarities between species composition of the hydrochoric seed pool and local standing riparian vegetation were used to evaluate the degree of longitudinal connectivity along river corridors and to isolate the relative contributions of local versus regional species pools to hydrochoric species composition. Furthermore, several synthetic attributes (longevity, origin, life‐form and dispersal mode) and species composition of riparian plant communities were examined to explore the effects of interrupted propagule dispersal on standing vegetation. We estimated that as many as 120 million seeds were transported via hydrochory along free‐flowing reaches of the Rocky Mountain streams in a single growing season. Seed concentration (seeds/m³) in the water column was reduced by 70–94% along reaches downstream from dams compared to free‐flowing reaches. The similarity in species composition of hydrochoric seeds and local standing vegetation was nearly two times greater downstream from reservoirs compared to upstream. This suggests that hydrochory complements local species pools by importing seeds from throughout the upstream catchment area along free‐flowing river reaches, but that hydrochoric seeds are derived primarily from local sources along regulated river reaches. Species richness recovers as a function of downstream distance from contributions of standing vegetation and seeds from tributary streams. Hydrochory may extend the period over which viable seeds of a parent population are dispersed. Even after dispersal of parent populations has terminated, seeds may continue to be available due to residence time in water transport. This extension of the ‘effective dispersal window’ of some species may exceed two weeks or more and may influence the likelihood of successful establishment. In this study, synthetic attributes of riparian vegetation did not differ significantly between free‐flowing and regulated reaches, whereas formal statistical comparisons of community composition upstream and downstream from reservoirs indicate that there are differences in community composition upstream and downstream from dams. These findings suggest that the consequences of 50 to 100 years of fragmentation result in community‐wide effects along Rocky Mountain streams and that these effects may be partially explained by dam‐caused disruption in connectivity of plant populations. Copyright © 2005 John Wiley & Sons, Ltd.     

PROJECTED FLOW ALTERATION AND ECOLOGICAL RISK FOR PAN‐EUROPEAN RIVERS

Projection of future changes in river flow regimes and their impact on river ecosystem health is a major research challenge. This paper assesses the implications of projected future shifts in river flows on in‐stream and riparian ecosystems at the pan‐European scale by developing a new methodology to quantify ecological risk due to flow alteration (ERFA). The river network was modelled as 33 668 cells (5′ longitude × 5′ latitude). For each cell, modelled monthly flows were generated for an ensemble of 10 scenarios for the 2050s and for the study baseline (naturalized flows for 1961–1990). These future scenarios consist of combinations of two climate scenarios and four socio‐economic water‐use scenarios (with a main driver of economy, policy, security or sustainability). Environmental flow implications are assessed using the new ERFA methodology, based on a set of monthly flow regime indicators (MFRIs). Differences in MFRIs between scenarios and baseline are calculated to derive ERFA classes (no, low, medium and high risk), which are based on the number of indicators significantly different from the baseline. ERFA classes are presented as colour‐coded pan‐European maps. Results are consistent between scenarios and show that European river ecosystems are under significant threat with about two‐thirds at medium or high risk of change. Four main zones were identified (from highest to lowest risk severity): (i) Mediterranean rim, southwest part of Eastern Europe and Western Asia; (ii) Northern Europe and northeast part of Eastern Europe; (iii) Western and Eastern Europe; and (iv) inland North Africa. Patterns of flow alteration risk are driven by climate‐induced change, with socio‐economics as a secondary factor. These flow alterations could be manifested as changes to species and communities, and loss of current ecosystem functions and services. Copyright © 2013 John Wiley & Sons, Ltd.     

Characterizing Sub‐Daily Flow Regimes: Implications of Hydrologic Resolution on Ecohydrology Studies

Natural variability in flow is a primary factor controlling geomorphic and ecological processes in riverine ecosystems. Within the hydropower industry, there is growing pressure from environmental groups and natural resource managers to change reservoir releases from daily peaking to run‐of‐river operations on the basis of the assumption that downstream biological communities will improve under a more natural flow regime. In this paper, we discuss the importance of assessing sub‐daily flows for understanding the physical and ecological dynamics within river systems. We present a variety of metrics for characterizing sub‐daily flow variation and use these metrics to evaluate general trends among streams affected by peaking hydroelectric projects, run‐of‐river projects and streams that are largely unaffected by flow altering activities. Univariate and multivariate techniques were used to assess similarity among different stream types on the basis of these sub‐daily metrics. For comparison, similar analyses were performed using analogous metrics calculated with mean daily flow values. Our results confirm that sub‐daily flow metrics reveal variation among and within streams that are not captured by daily flow statistics. Using sub‐daily flow statistics, we were able to quantify the degree of difference between unaltered and peaking streams and the amount of similarity between unaltered and run‐of‐river streams. The sub‐daily statistics were largely uncorrelated with daily statistics of similar scope. On short temporal scales, sub‐daily statistics reveal the relatively constant nature of unaltered stream reaches and the highly variable nature of hydropower‐affected streams, whereas daily statistics show just the opposite over longer temporal scales. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

SPATIAL VARIATION OF STRUCTURAL AND FUNCTIONAL INDICATORS IN A LARGE NEW ZEALAND RIVER

The ecological responses of large rivers to human pressure can be assessed at multiple scales using a variety of indicators, but little is known about how the responses of ecological indicators vary over small spatial scales. We sampled phytoplankton, zooplankton and macroinvertebrates and measured river metabolism and cotton strip breakdown rates (loss in tensile strength) in contrasting habitats along a 21‐km urban‐industrial reach on a constrained section of the Waikato River, New Zealand's longest river. Rates of gross primary production (2.8–7.8 g O₂/m²/d) and ecosystem respiration (3.5–12.7 g O₂/m²/d) did not differ consistently between near‐shore (2–3 m from river side) and far‐shore (ca. 10 m from side) locations, urban and industrial reaches or between autumn and spring sampling occasions. Rates of cotton decay (?k) ranged from 0.014 to 0.112 per day and were typically faster at far‐shore locations and in the section of river receiving industrial inputs, but slower in spring compared with autumn. Nonmetric multidimensional scaling analysis of phytoplankton and zooplankton data did not reveal spatial patterns relating to pressure or location (embayment, edge, mid‐river). However, the macroinvertebrate ordination suggested distinct communities for the mid‐river benthos compared with near‐shore communities and a distinction between sites in the urban reach and the industrial reach. Our results suggest that large‐river macroinvertebrate communities and cotton decay rates can be influenced to varying degrees by reach‐scale pressures and local habitat conditions. Monitoring designs in spatially complex rivers should account for habitat heterogeneity that can lead to differences in structural and functional indicator responses. Copyright © 2012 John Wiley & Sons, Ltd.     

Benthic Response to Flow Alteration in a New Mexico Arid Mountain Stream

Past and current pressure on streams and rivers for consumptive use requires the development of tools and decision‐making processes for water managers to minimize impacts on ecological function. This paper examines the utility of modeling benthic biomass in relation to benthic macroinvertebrate (BMI) community attributes for water resource management scenarios in the Cliff‐Gila Valley of the Gila River, New Mexico, USA. The river benthos biomass model (RivBio) was used in conjunction with hydraulic modeling to predict growth and decline of benthic biomass. BMI community attributes were compared along gradients of hydrologic impact (successive existing diversions) in the Cliff Gila Valley and were compared to community attributes in similar regional streams. Benthic biomass was minimally affected by proposed diversions at flows above 4.25 cms (150 cfs), but was severely reduced downstream because of existing diversions during lower flow periods. Riffle habitat was disproportionately affected during extreme low and interrupted flow, which may have resulted in BMI communities shifted towards multi‐habitat generalists that can persist in lentic conditions. Flow augmentation from proposed diversions and storage would greatly mitigate these existing biomass losses by providing consistent base flow and lotic conditions in riffle habitat. Both benthic biomass and BMI community endpoints were useful when comparing water management scenarios. Copyright © 2016 John Wiley & Sons, Ltd.