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.     

The role of riparian vegetation and woody debris in the development of macroinvertebrate assemblages in streams

Riparian vegetation development and macroinvertebrate assemblages were studied in 16 streams formed between 35 and 230 years ago, following glacial recession in Glacier Bay National Park, southeast Alaska. Riparian vegetation established most rapidly in streams where flow variation in downstream reaches was buffered by a lake. Riparian vegetation development was positively correlated with lower bank stability, but was independent of stream age. Roots and branches of riparian vegetation trailing into streams (trailing riparian habitat—TRH) were shown to be an important habitat for a number of macroinvertebrate taxa. In young and unstable streams, TRH was colonized mainly by Plecoptera whereas in more stable lake‐influenced streams Simuliidae dominated. Significant coarse woody debris (CWD) accumulations were not observed until after approximately 130 years of stream development had occurred when certain channel features, such as gravel bars, were stabilized by dead wood. Where dead wood was present, opportunistic wood taxa were abundant, even in the younger streams. However, a xylophagous species, Polypedilum fallax, was not recorded until streams were over 100 years old. Two‐way indicator species analysis (TWINSPAN) using presence/absence of macroinvertebrate taxa on TRH, initially divided streams into lake and non‐lake systems, but subsequent divisions were consistent with differences in stream age. TWINSPAN of macroinvertebrate assemblages on dead wood again highlighted differences in stream age. Canonical correspondence analysis indicated that bed stability and stream age were the most important environmental variables influencing macroinvertebrate distribution on TRH. Trailing riparian habitat was most abundant in moderately unstable streams where it facilitates invertebrate colonization. CWD contributes markedly to channel stabilization, provides habitat for invertebrate xylophages, and confers additional habitat complexity. Maximum levels of CWD are predicted to occur in non‐lake streams after approximately 300 years, but at least a further 100 years will be required in stable streams below lakes where dead wood entrainment is not enhanced by flooding, channel migration and bank undercutting. A conceptual model summarizing the role of TRH and CWD on stream development in Glacier Bay is presented. Copyright © 2005 John Wiley & Sons, Ltd.     

Macroinvertebrate community structure and function associated with large wood in low gradient streams

Large woody debris (wood) plays a number of important roles in forested stream ecosystems. Wood in streams provides habitat and flow refugia for fish and invertebrates, and is a site of biofilm production that serves as food for grazing organisms. Logs added to streams are rapidly colonized by invertebrates, and this habitat alteration is accompanied by changes in community composition and functional processes. A multiple habitat, qualitative sampling approach was employed to evaluate macroinvertebrate communities associated with wood habitats in 71 stream reaches in central Michigan and southeastern Minnesota, two agricultural regions in the midwestern United States. Macroinvertebrate taxa were classified with respect to behaviour (e.g. sprawler, clinger, swimmer), as well as trophic/feeding characteristics. These traits were used to examine community structure as a function of wood abundance and distribution. Although wood is not abundant in these streams and logs are generally small in size, wood is a very important habitat in both Michigan and Minnesota: 86% and 95% of the total taxa encountered at Michigan and Minnesota study sites, respectively, were found in wood habitats. Differences in regional patterns in the distribution of taxa across habitats were observed between Michigan and Minnesota. These are believed to result from differences in the number of habitat types available, and the dominant substrate composition. Local invertebrate diversity increased in Michigan, but not Minnesota, with the presence of wood habitats in streams. The presence of wood at a site increased the average taxa richness by 15 and 10 taxa in Michigan and Minnesota, respectively. Macroinvertebrate behavioural attributes and functional traits associated with wood habitats suggest that community traits may vary due to both local difference in flow and the location of wood in the channel. Copyright © 2003 John Wiley & Sons, Ltd.     

Effects of stream diversion on riffle macroinvertebrate communities in a Maui,Hawaii, stream

The continual demand for freshwater by industry (e.g. tourism) and agriculture, a growing population, and increasing development over the past 100 years has resulted in the construction of diversions within many streams of Hawaii. The main objective of this study was to evaluate the impact of stream diversions on riffle macroinvertebrate communities. Benthic macroinvertebrate larval populations were compared above and below a diversion in Iao Stream, Maui, Hawaii, from April to August 2000. During this summer approximately 92–97% of daily stream flow was diverted from Iao Stream. Three taxa, Procanace sp. (Diptera: Canacidae), Atyoida bisulcata (Crustacea: Decapoda), and Amphipoda (Crustacea), were only collected above the diversion. However, the most numerous taxa, Chironomidae (63–64% of the total macroinvertebrate community), Hydroptila arctia (Trichoptera: Hydroptilidae; 15%), and Cheumatopsyche pettiti (Trichoptera: Hydropsychidae; 8%), were found both above and below the diversion. The relative percentage abundance of these dominant taxa remained relatively consistent above and below the diversion over the study period. However, the mean total density of individual dominant taxa was greater above the diversion. The mean total macroinvertebrate density above the diversion was 46% greater than below the diversion (Student t‐test: df = 30, t = ?3.22, p > 0.01). No correlation was found between temperature and density. A positive correlation was detected between Froude number and mean total macroinvertebrate density. Overall, the reduction in macroinvertebrate diversity and in individual and total density below the diversion suggest that trophic interactions, and thus energy flow, could be affected by reduced flow in Hawaiian streams. The information gained from this study will contribute to knowledge on Hawaiian stream ecosystems, help to create minimum instream flow standards for stream restoration, and will provide information for future freshwater management issues on the Hawaiian islands. Copyright © 2002 John Wiley & Sons, Ltd.     

Mitigation of impacts of cattle access on stream ecosystems: Efficacy of fencing

Headwater streams can constitute up to 80% of river channel length and are vulnerable to anthropogenic pressures due to their high connectivity to adjacent land, large relative catchment size and low dilution capacity. In these environments, unrestricted cattle access is a potentially significant cause of water quality deterioration, resulting from increases in stream bank erosion, riparian damage and sediment deposition among others. Several studies have reported improvements in the physico-chemical and hydromorphological conditions of streams following the elimination of cattle access; few, however, have focussed on the ecological impacts of such management practices. Here, such impacts are assessed. The study explores the short-term effects of cattle exclusion by comparing habitat conditions, sediment deposition and instream macroinvertebrate communities upstream and downstream of cattle access points prior to, and 1 year following exclusion via fencing. The long-term effects are also measured by reassessing a small stream catchment entirely fenced off from cattle access in 2008 under a dedicated management plan. In the short term, cattle exclusion led to a reduction in deposited sediment downstream of cattle access points and a related homogenisation of macroinvertebrate community structure between upstream and downstream of cattle access points. Increased abundances of specific indicator taxa (Ancylus fluviatilis, Glossosomatidae and Elmidae) in the fenced catchment following 9 years of exclusion highlight the long-term ecological benefits of such mitigation practices. These findings highlight the importance of incentivised agri-environment measures in reducing the negative impacts of cattle access to vulnerable aquatic ecosystems.     

BENTHIC COMMUNITY RESPONSES TO WATER REMOVAL IN TROPICAL MOUNTAIN STREAMS

Mountain streams that originally supported Hawaiian cultural practices have been diverted for development, agriculture and tourism for over 150 years. Habitat characteristics and benthic macroinvertebrate community responses to water withdrawal were studied in four West Maui Mountain watersheds. We compared riffle and cascade habitats upstream and downstream of the highest‐elevation diversion in each stream and further compared streams to understand variation among watersheds. Riffles were shallow areas with moderate flow, whereas cascades had high‐velocity water flowing over boulders and were separated into torrenticolous (submerged) and amphibious (splash zones on adjacent exposed rock) microhabitats. Among streams, downstream discharge was reduced by 84–99%, flow velocity was four times greater upstream, and depth was 50% lower downstream. There was a significant 44% reduction in downstream macroinvertebrate density (t = 3.261, df = 136, p = 0.0014); however, density did not significantly differ among streams (F = 1.95, df = 3, p = 0.125). Habitat‐corrected density, based on total available habitat area, indicated significantly greater proportions of native taxa in amphibious microhabitats compared with riffle and torrenticolous habitats. Non‐native Chironomidae and Trichoptera (Cheumatopsyche sp. and Hydroptila sp.) were dominant (>95%) and ubiquitous in riffles, whereas native Limonia sp. dominated (30%) amphibious microhabitats. Macroinvertebrate community structure varied among streams, sites and microhabitats, indicating inconsistent response to water withdrawal, dependent upon watershed size and microhabitat conditions. Our findings contribute to water management and restoration efforts focused on conservation of native species and habitat integrity in tropical streams worldwide. Copyright © 2013 John Wiley & Sons, Ltd.     

Seasonal differences in diversity of macroinvertebrate and fish taxa in a Midwestern stream

Most biomonitoring projects focus on single species groups at time scales either too short or too coarse to detect intra‐annual oscillations in biodiversity. Using a multifaceted approach, we compared diversity indices of larval macroinvertebrate families and fish species in a Midwestern stream during spring and fall of 2009–2013 and discovered contrasting patterns in α and β diversities between the seasons for the two taxa groups. Compared with spring, both α and β diversities were significantly higher during fall for macroinvertebrates; on the contrary, only α diversity differed between the seasons for fishes. For both taxa, we partitioned the overall β diversity to identify contributions of temporal and spatial β diversities on the observed differences. The observed patterns for macroinvertebrates were likely the result of season acting as environmental filter, but stochastic dispersal and recruitment processes were likely more important in driving fish diversity patterns. In light of widespread conservation and restoration efforts in the Midwestern streams, it seems prudent to study community composition frequently so that baseline α and β diversities can be obtained for organisms at different taxonomic levels and during different seasons.     

Structural and functional changes of tropical riffle macroinvertebrate communities associated with stream flow withdrawal

Tropical island streams worldwide are threatened by existing or proposed dams and diversions that remove freshwater for human use; yet, there have been few studies that address the effects on aquatic communities. The objective of this study was to quantify changes in tropical macroinvertebrate communities associated with stream flow withdrawal. Benthic macroinvertebrates were collected from riffle habitats located above and below a stream diversion on Maui, Hawaii, from June to August 2000. Native and introduced taxa were identified from both locations. The most dominant taxon was midges (Diptera: Chironomidae) followed by two introduced caddisflies, Cheumatopsyche analis (Banks) (Trichoptera: Hydropsychidae) and Hydroptila potosina (Buenoa‐Soria) (Trichoptera: Hydroptilidae). A native shrimp, Atyoida bisulcata, and beach fly, Procanace sp. (Diptera: Canacidae), were either eliminated from or significantly reduced below the diversion. Mean total macroinvertebrate densities were greater above (13 357 individuals/m²) the diversion compared to below (10 360 individuals/m²). Mean total macroinvertebrate biomass was significantly reduced by 60 per cent below the diversion, but specific taxa did not show this effect. These results suggest that diverted stream flow limited macroinvertebrate colonization and growth, expressed as reduced community density and biomass, which may alter the structure and function of other trophic levels within tropical stream food webs. Copyright © 2008 John Wiley & Sons, Ltd.     

Defining and Testing Targets for the Recovery of Tropical Streams Based on Macroinvertebrate Communities and Abiotic Conditions

Here, we set target values to measure the ecological improvement of streams, based on invertebrate communities, riparian vegetation, instream habitat conditions and water chemistry. The study area is a large tropical catchment (Rio das Velhas, Minas Gerais, Brazil) affected by pastures, mining areas and a large urbanized area but also includes natural protected areas. Two stream types were found in the catchment, based on stream size, elevation, climate and geology with significantly different macroinvertebrate communities. In spite of a marked wet/dry seasons' climatic pattern, that does not result in the segregation of communities. Four classes of global degradation (IV—bad to I—good condition) were defined based on the available abiotic information, corresponding to a gradient in structure and biotic metrics of macroinvertebrate communities, matching the current knowledge on taxa sensitivity to pollution and general disturbance. Class I corresponds to target conditions to be achieved under restoration programmes. Using this approach, we were able to detect an improvement of abiotic conditions in four urban streams that benefited from enhancement measures in 2007–2008. However, invertebrate communities improved clearly in only one site (biotic metrics and community structure). Our study highlighted that good water quality alone is not enough and that only the combined effect of water quality, riparian vegetation and instream habitat condition enhancement resulted in the improvement of invertebrate communities. An important limiting factor for macroinvertebrate communities' recovery may be the distance to source populations. We concluded that the combined use of biological and abiotic target values for measuring the recovery of streams is needed to fully achieve an ecological restoration. This approach can also be valuable in the regular monitoring of streams to assess stream degradation. Target values based on other biological elements, such as fishes and algae, and functional processes could also contribute to define more global and realistic goals. Copyright © 2013 John Wiley & Sons, Ltd.     

Stay with the flow: How macroinvertebrate communities recover during the rewetting phase in Alpine streams affected by an exceptional drought

Droughts are affecting an increasing number of lotic ecosystems worldwide due to the combined effects of climatic and anthropogenic pressures. Unlike naturally intermittent rivers, where the drying phase is a part of the annual flow regime, water scarcity in Alpine rivers represents a relatively recent phenomenon and, therefore, a major threat for the biodiversity of these lotic ecosystems. However, Alpine stream community response to drought is still poorly investigated. Here, we assess the recovery of macroinvertebrates in two Alpine streams after a supraseasonal drought. As water returned, a total of 10 sampling sessions were carried out, and temporal patterns in diversity, density, and taxonomic composition of benthic communities, as well as in the percentage of functional feeding groups, were investigated. We found that the resistance of invertebrate communities in Alpine streams is generally low: drought markedly reduced the diversity and density of macroinvertebrates. Conversely, our results suggest that the passive dispersal by drift from the upstream river sections seems the most probable mechanism promoting the post‐drought recovery. Nevertheless, this resilience ability appears to be stream specific and influenced by intrinsic stream characteristics, including the flow permanence and distance from the nearest upstream perennial reach. This work sheds light on the ecological consequences of droughts on macroinvertebrate communities. As flow intermittency in Alpine areas is expected to intensify under current global change scenarios, results of this study provide important information to predict changes in the taxonomic composition and diversity of macroinvertebrate communities.     

Physical habitat structure in Danish lowland streams

Dredging or channelization has physically modified the majority (90%) of the 64 000 km of Danish stream network with substantial habitat degradation as a result. Analyses of physical habitat structure in streams, biota, catchment features and regional differences in hydrology, topography and geology have never been carried out in Denmark. Therefore, there is little knowledge of processes, interactions and patterns across the different scales. Physical habitats, catchment parameters and macroinvertebrates were sampled at 39 sites in three major river systems during summer and winter 1993. In‐stream physical conditions and catchment attributes affect the physical habitat structure in Danish lowland streams. Local differences in hydrology, land use, catchment topography and soil types correlated to the in‐stream physical habitat parameters. Local differences in hydrology and topography resulted in a separation of the Suså streams with respect to physical habitats. Mud deposition was pronounced at sites with low discharge and low near‐bed current velocity. Low mud cover was primarily associated with streams with high discharge located in pristine catchments. Stability in the streams was therefore closely linked to in‐stream deposition of fine sediment. Generally, macroinvertebrate community diversity increased as discharge increased. Mud cover negatively affected macroinvertebrate diversity and EPT taxon richness. Regional physical habitat structure and macroinvertebrate community structure were primarily associated with local variations in hydrology, geology and topography. Low‐energy streams were primarily located in the Suså river system and the high‐energy streams in the Gudenå and Storå river systems, leading to extensive deposition of mud during summer. Streams in the Suså river system generally had lower diversity and species richness compared to the streams in the Gudenå and Storå river systems. Hydraulic conditions and substratum dynamics in streams are important when managing lowland streams. This study therefore analysed interactions and parameter correlations between physical habitats, stream stability and catchment attributes as well as macroinvertebrate community structure across multiple scales. Copyright © 2004 John Wiley & Sons, Ltd.     

Invertebrate response to impacts of water diversion and flow regulation in high‐altitude tropical streams

Water supply systems are critical infrastructure that provides food and energy security for developed societies. The operation of reservoirs (flow regulation) and water intakes (water diversion) has known negative impacts on aquatic ecosystems; however, quantification of ecological impacts and examination of these two types of flow alteration remain a developing area of research. We investigated the individual and combined impact of flow regulation and water diversion on stream ecosystem integrity, the freshwater macroinvertebrate community, and the population structure of flow‐sensitive insects. For 2 years, we monitored quarterly discharge, physical and chemical stream conditions, and benthic invertebrates of four high‐altitude tropical streams that are part of the water supply system of Quito, Ecuador. Flow regulation caused a loss of the hydrological seasonality of these streams, including a decrease in stream depth and biotic quality. Water diversion caused a decrease in dissolved oxygen and overall ecosystem integrity. Freshwater invertebrate density and richness decreased as a result of water diversion and flow regulation. The combined flow alteration in these streams decreased the density of nymphal stages of the widely distributed mayfly Andesiops peruvianus. Given the societal needs for food and energy security, water management for diversion (e.g., irrigation) and in‐line storage practices (e.g., hydroelectric dams) are anticipated to increase. This research suggests that the negative environmental impacts of flow alteration could be mitigated with discharge releases designed to approximate the natural hydrologic regime of undisturbed streams.     

Combining taxonomic and functional approaches to assess land-use impacts on macroinvertebrate assemblages and improve bioindication

Most studies exploring land use impacts have focused on taxonomic metrics, but interest in the functional approach has increased because it helps to understand the relationships between community structure and functioning of aquatic ecosystems. We evaluated how functional and taxonomic approaches, and the association between them, contribute to assessing the effects of land use on macroinvertebrate assemblages of lowland streams. We sampled benthic macroinvertebrates in 17 sites with different land uses (agricultural, peri-urban, and extensive livestock) in Buenos Aires, Argentina. We computed the taxonomic metrics and biotic indexes as well as functional richness (FRic), divergence (FDiv), dispersion (FDis), and Rao diversity indexes for each site. We performed general linear mixed models to compare land-uses, a redundancy analysis, and also performed correlation analysis between taxonomic and functional indexes. Taxonomic richness was significantly higher in extensive livestock than in the other two land uses, while Shannon diversity was significantly different between land uses (extensive livestock > peri-urban > agriculture). FRic and FDiv were significantly lower in peri-urban land use than in agricultural and extensive livestock sites. Only taxonomic richness showed a significant and positive relationship with FRic, FDis, and Rao, but they fit better to a logarithmic function. Therefore, an increase in taxonomic richness and Shannon diversity did not necessarily imply an increase in the functional aspects of the macroinvertebrate assemblage. Using only one of these approaches could lead to partial evaluations and loss of information. Combining them could improve bioindication and predictive potential and help assess the effects of multiple stressors on freshwater ecosystems to improve biomonitoring.     

Removal of the Invasive Shrub,Lonicera Maackii,from Riparian Forests Influences Headwater Stream Biota and Ecosystem Function

Riparian forests and streams are interlinked by cross‐system subsidies and alterations of the terrestrial environment can have substantial effects on aquatic biota and ecosystem function. In the Midwestern USA, the exotic shrub Lonicera maackii (Amur honeysuckle) has successfully invaded many riparian habitats, creating near‐monocultures in some locations. This terrestrial invasion has strong potential to modify cross‐system subsidies and impact stream ecosystems. We removed L. maackii from a riparian forest to assess impacts on the aquatic environment. In August 2010, removal occurred along a 150 m stream reach, 10 m downstream of a non‐removal reach, before natural leaf senescence. Over 74 days, in‐stream leaf litter [organic matter (OM)] was collected weekly from plots located in riffles (five/reach). Benthic algal biomass, above stream canopy cover, and macroinvertebrate density were measured for 18 months. L. maackii removal was associated with decreased canopy cover and a significant increase in total in‐stream leaf OM in early autumn (P < 0.05). Removal also differentially influenced the timing and abundance of specific leaf litter genera within the stream (P < 0.05). Macroinvertebrate density was significantly higher in the removal reach, especially during autumn 1 year after removal (P = 0.0294). In both reaches, macroinvertebrate density peaks lagged behind benthic algal biomass peaks. In summary, the removal of an invasive riparian shrub influenced the timing, deposition, quality and abundance of leaf litter habitat into a headwater stream, ostensibly driving bottom‐up effects on aquatic primary producer biomass and the macroinvertebrate community. Copyright © 2014 John Wiley & Sons, Ltd.     

Spatial distribution and geomorphic condition of fish habitat in streams: an analysis using hydraulic modelling and geostatistics

Reach‐scale physical habitat assessment scores are increasingly used to make decisions about management. We characterized the spatial distribution of hydraulic habitat characteristics at the reach and sub‐reach scales for four fish species using detailed two‐dimensional hydraulic models and spatial analysis techniques (semi‐variogram analyses). We next explored whether these hydraulic characteristics were correlated with commonly used reach‐scale geomorphic assessment (RGA) scores, rapid habitat assessment (RHA) scores, or indices of fish biodiversity and abundance. River2D was used to calculate weighted usable areas (WUAs) at median flows, Q₅₀, for six Vermont streams using modelled velocity, depth estimates, channel bed data and habitat suitability curves for blacknose dace (Rhinichthys atratulus), brown trout (Salmo trutta), common shiner (Notropis cornutus) and white sucker (Catostomus commersoni) at both the adult and spawn stages. All stream reaches exhibited different spatial distributions of WUA ranging from uniform distribution of patches of high WUA to irregular distribution of more isolated patches. Streams with discontinuous, distinct patches of high score WUA had lower fish biotic integrity measured with the State of Vermont's Mixed Water Index of Biotic Integrity (MWIBI) than streams with a more uniform distribution of high WUA. In fact, the distribution of usable habitats may be a determining factor for fish communities. A relationship between predicted WUAs averaged at the reach scale and RGA or RHA scores was not found. Future research is needed to identify the appropriate spatial scales to capture the connections between usable patches of stream channel habitat. Copyright © 2008 John Wiley & Sons, Ltd.     

Potential ecological effects of water extraction in small,unregulated streams

River regulation can have various effects on the natural flow regime, however the most obvious and perhaps pronounced hydrological effect is the reduction of total water discharge. Whilst there has been an increasing number of studies investigating the impacts of river regulation on lowland rivers, few studies have specifically investigated the effects of water extractions on small upland streams. In this study, we experimentally examined the effects of short‐term, summer water extractions from small, unregulated streams. Five 30 m reaches were experimentally manipulated to divert a proportion of the total stream flow, and another five 30 m reaches were designated as controls, in the Yea River catchment, Victoria, Australia. The percentage of total discharge diverted from each experimental reach varied through time and between creeks (28–97%), with discharge always significantly reduced compared to control locations. All sites were monitored for available habitat, biofilm, water quality and macroinvertebrate diversity and density, fortnightly during February and March 2004. Despite the range of total stream volumes being extracted, the manipulation altered important ecological components of these unregulated creeks, including changes in physical habitat features (reduced stream wetted area and maximum stream depth) and reduced dissolved oxygen concentrations. Biofilm parameters showed a slight increase in diverted reaches, but were not statistically different from the controls. There was no statistical difference in total density of macroinvertebrates or EPT taxa; however, the density of Austrocercella mariannae (Notonemouridae) was significantly reduced in diverted reaches. Macroinvertebrate family level diversity, and the family diversity of grazers and shredders was reduced in diverted reaches. This study demonstrates that there are likely to be significant ecological impacts of extracting water in unregulated creeks. Whilst this study has demonstrated the need to consider environmental water requirements in unregulated streams, further studies are required to inform the debate about the volume, timing and predicted ecological response with improved environmental water. Copyright © 2006 John Wiley & Sons, Ltd.     

Massive Growth of the Invasive Algae Didymosphenia Geminata Associated with Discharges from a Mountain Reservoir Alters the Taxonomic and Functional Structure of Macroinvertebrate Community

The objective of this paper is to determine the alteration of the taxonomic composition and functional structure of macroinvertebrate community associated with a massive growth of the invasive algae Didymosphenia geminata downstream of a mountain reservoir (Pajares Reservoir, La Rioja, Northern Spain). As the massive growth of the alga disappears a few kilometres downstream of the reservoir associated with the input of nutrients from a nearby village sewage, we may compare the community composition between nine stations in three different conditions: three stations heavily affected by the presence of D. geminata, three further downstream stations without the algal massive growth but affected by river regulation and three control stations (unregulated and without the algae). Results show a significant disturbance of the composition and structure of macroinvertebrate community in sites affected by the stream flow regulation downstream of the dam compared with unregulated streams, but the alterations are more dramatic in the area where the growth of D. geminata is massive because of the total substrate occupation by the algal filaments. Scrapers and others invertebrates living on the coarse substrate are especially affected at such sites. Moreover, an important increase in the relative abundance of chironomids is associated with the algal massive growth, especially in case of Eukiefferiella devonica and Cricotopus spp., reducing the assemblage diversity and leading to the taxonomic and functional homogenization of the community. Changes in the reservoir management (such as releasing the water from surface rather than from the hypolimnion) may be useful to control the massive growth of D. geminata and thus reducing the effects of river regulation on macroinvertebrate assemblage composition. Copyright © 2014 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.     

First steps in developing a multimetric macroinvertebrate index for the Ohio River

The causes of degradation of aquatic systems are often complex and stem from a variety of human influences. Comprehensive, multimetric biological indices have been developed to quantify this degradation and its effect on aquatic communities, and measure subsequent recovery from anthropogenic stressors. Traditionally, such indices have concentrated on small‐to medium‐sized streams. Recently, however, the Ohio River Fish Index (ORFIn) was created to assess biotic integrity in the Ohio River. The goal of the present project was to begin developing a companion Ohio River multimetric index using benthic macroinvertebrates. Hester–Dendy multiplate samplers were used to evaluate benthic macroinvertebrate assemblages in relation to a gradient of water quality disturbance, represented by varying distances downstream of industrial and municipal wastewater outfalls in the Ohio River. In August 1999 and 2000, samplers were set every 100 m downstream of outfalls (12 outfalls in 1999, 22 in 2000) for 300–1000 m, as well as at upstream reference sites. Candidate metrics (n = 55) were examined to determine which have potential to detect changes in water quality downstream of outfalls. These individual measures of community structure were plotted against distance downstream of each outfall to determine their response to water quality disturbance. Values at reference and outfall sites were also compared. Metrics that are ecologically relevant and showed a response to outfall disturbance were identified as potentially valuable in a multimetric index. Multiple box plots of index scores indicated greater response to outfall disturbance during periods of low‐flow, and longitudinal river‐wide trends. Evaluation of other types of anthropogenic disturbance, as well as continued analysis of the effects of chemical water quality on macroinvertebrate communities in future years will facilitate further development of a multimetric benthic macroinvertebrate index to evaluate biotic integrity in the Ohio River. Copyright © 2007 John Wiley & Sons, Ltd.     

Potential Impacts of Stream Crossing Traffic On Macroinvertebrate Communities in the Missouri Ozark River

Depending on intensity, physical disturbance can either decrease or increase diversity of stream macroinvertebrate communities. Recreational activities in parks are one component of physical disturbance. Our objective was to evaluate the effects of stream crossings and recreational traffic on macroinvertebrate assemblages. Five stream‐crossing sites were sampled during winter and summer in the Current River, Ozarks National Scenic Riverways, Missouri, USA. Stream‐crossing traffic was assessed using trail cameras. At each site, macroinvertebrates were collected from four locations: riffle upstream of crossing, riffle immediately downstream of crossing and second and third riffles downstream of crossing. We compared sites and locations within sites using standard metrics (taxa richness, Ephemeroptera, Plecoptera and Trichoptera richness, biotic index and diversity) and their composite stream condition index (SCI) plus multivariate analyses (Nonmetric multidimensional scaling and correlations). Stream crossings had no detectable impacts on macroinvertebrate communities in winter, but in summer location, effects were present. Patterns in SCI scores across locations varied among sites, with no consistent declines in macroinvertebrate diversity downstream of crossings. Longitudinal stream effects dominated over potential stream‐crossing effects on macroinvertebrate communities. Overall, high SCI scores indicated that current levels of stream crossings and traffic in this scenic riverway do not pose a threat to macroinvertebrate communities at the spatial and temporal scale of this study. Copyright © 2015 John Wiley & Sons, Ltd.