Macroinvertebrate assemblages at mesohabitat scale in small sized volcanic siliceous streams of Central Italy (Mediterranean Ecoregion)

According to the guidelines of the European Water Framework Directive, assessment of the ecological quality of streams and rivers should be based on type-specific reference conditions. Moreover to support biological indicators an hydromorphological analysis is also requested for each river type. The rationale for including an habitat assessment in biomonitoring study is that a biological community can be influenced by habitat quality just as water chemistry.In the present work benthic macroinvertebrates were analysed in a specific river type of Central Italy (small-sized streams, volcanic-siliceous), to identify taxa assemblages at the mesohabitat scale and to test how common measures of benthic community used in biomonitoring differ between riffles and pools in order to evaluate if differences may influence water quality classification.Macroinvertebrates were collected in 10 selected streams, covering the whole quality range present in the geographic area from ‘reference sites’ to human-impacted sites, along a pool–riffle sequence following a multihabitat sampling protocol.We compared assemblage of macroinvertebrates found in different mesohabitats using principal component analysis (PCA). Similar site grouping was obtained in riffle, pool and abiotic analysis.The measures of diversity and abundance were used as replicates in ANOVA analysis to test differences between pools and riffles within the groups of sites. There were no significant differences in terms of taxa richness and total abundance.When we compared the abundance of each taxon we found significant differences only in the group of reference sites with 18 taxa (about 25%) that showed a significant habitat preference.Our findings support that macroinvertebrates assemblages reflected primarily the environmental conditions and differences at mesohabitat scale are strongly correlated to hydromorphological condition and are maximized in reference sites. However such differences do not influence the ecological status assessment in this typology.     

Zambian Invertebrate Scoring System (ZISS): A macroinvertebrate-based biotic index for rapid bioassessment of southern tropical African river systems

An extensive survey of tropical rivers, conducted during 2009–2012 throughout Zambia, collected 151 samples of benthic macroinvertebrates, located on 95 rivers in six of the nine freshwater ecoregions. Associated data for physico-chemistry, human activities and ecosystem stressors were collected. Data were used to develop and test a new Rapid Bioassessment Protocol (the Zambian Invertebrate Scoring System: ZISS) for assessment of water quality and river condition in both wadeable and non-wadeable rivers. ZISS, which is based on the South African Scoring System (SASS), includes a total of 85 taxa, of which 79 are shared with SASS. Assignment of sensitivity weightings to new ZISS taxa was based on sensitivity weightings of closely related SASS families; known life-history modes and anatomical adaptations; and correlation of occurrence to impact ratings. The ability of the ZISS to measure impacts was assessed by determining the relationships between ZISS metrics and impacts. ZISS data for the Kafue River demonstrated the efficacy of the ZISS for detecting moderate to high impacts on water quality and river condition. ZISS represents a major step in developing a user-friendly, widely applicable, macroinvertebrate-based biotic index, which can provide easily interpretable assessments of river condition for southern tropical African rivers.     

Addressing a gap in the Water Framework Directive implementation: Rocky shores assessment based on benthic macroinvertebrates

A gap in the European Water Framework Directive (WFD) is addressed, aiming for the development of an ecological quality status assessment tool based solely on the Biological Quality Element benthic macroinvertebrates from intertidal rocky shores. The proposed Rocky shore Macroinvertebrates Assessment Tool (RMAT) was tested and validated along disturbance gradients (organic enrichment). During the whole process, the response of widely used metrics (e.g. Hurlbert index, Shannon-Wiener index, AZTI’s Marine Biotic Index; Bentix biotic index) and models (i.e., metrics combined) was compared to results provided by the Marine Macroalgae Assessment Tool to the same sampling sites.The RMAT is a multimetric index compliant with the WFD based on the benthic macroinvertebrates community, combining ‘abundance’ (Hurlbert index) and ‘taxonomic composition’ (Bentix index using density and biomass data) metrics. It performed well along anthropogenic disturbance gradients, showing ecological quality increasing from close to far away from the disturbance.The RMAT is a promising tool for rocky shore ecological assessment in the scope of the WFD or other monitoring activities worldwide.     

Restoration of the Kissimmee River: A Conceptual Model of Past and Present Fish Communities and Its Consequences for Evaluating Restoration Success

Efforts to restore fish communities of the Kissimmee River will require carefully defined criteria for assessing success. A goal of regaining communities mirroring those in the historical river may not be an appropriate target because the ecological conditions of the river before channelization are poorly known. The Kissimmee River is in a biogeographic region historically low in fish diversity, and no comparable rivers in that region remain substantially unaltered by human activity to permit their use as reference sites indicative of conditions in the Kissimmee before channelization. I propose alternative criteria for assessing restoration success emphasizing expectations for ecosystem function in similar floodplain rivers. Assessing ecosystem function will be less simple than assessing criteria such as fish condition or density of selected species. But criteria based solely on fish-population characteristics cannot be justified quantitatively. Information integrated from several levels of biotic organization (individuals, populations, communities, and systems) should be drawn upon in making conclusions about restoration success. I develop a conceptual model to outline aspects of ecosystem function that could serve as a basis for evaluation of the restoration of fish communities of the Kissimmee River. The model focuses on the dynamics of the flux of floodplain-channel nutrients and the movement of larvae, juvenile, and adult fishes and macroinvertebrates. The present community may be dominated more by species tolerant of low-oxygen conditions, such as gar and bowfin, than the restored community will be. I propose that nest sites may be the limiting recruitment success of substrate spawning species in the channelized river and that these species, including sunfish and large-mouth bass, will increase in abundance after restoration. Also, species relying on floodplain habitats, including sun-fish species, darters, and some minnows, may also increase in frequency with restoration of floodplain-channel hydro-logical conditions and habitats. The observation that no species are known to have disappeared from the Kissimmee River, and its relatively simple community structure compared to rivers of comparable size elsewhere, are encouraging for prospects of successful restoration.     

Comparative assessment of indices of freshwater habitat conditions using different invertebrate taxon sets

Monitoring changes in population levels of a wide range of species in biodiversity research and conservation requires practical, easy-to-use and efficient assessment and monitoring methods. Dragonflies (Insecta: Odonata) are a valuable tool for assessing aquatic systems and have been used as indicators of ecological health, ecological integrity, and environmental change, including climatic change, as well as indicators of habitat recovery. We field-tested a freshwater ecological integrity index, the Dragonfly Biotic Index (DBI), based on dragonfly assemblages at the local scale, and compared the DBI to a biodiversity index (average taxonomic distinctness, AvTD) as well as to a standard freshwater benthic macroinvertebrate-based freshwater health index (South African Scoring System, using Average Score Per Taxon, ASPT). We sampled 20 river sites, selected a priori. Adult dragonflies and benthic macroinvertebrates were collected using standardized methods. Environmental variables were collected in situ, and water samples taken. Temperature and pH were the most important physical environmental variables in explaining the assemblage structure, and we found significant abiotic–biotic relationships, as well as biotic–biotic relationships. Overall, dragonflies were more sensitive to changes in river condition than were macroinvertebrates, in part because they were responding at the species rather than higher taxonomic level. AvTD scores did not show any significant relationship with changes in river condition. Furthermore, sites with low biotic scores (indicating disturbance) had high AvTD values. In contrast, DBI site value and ASPT scores were highly significantly correlated. We conclude that dragonfly assemblages in the form of a DBI are an excellent tool for environmental assessment and monitoring freshwater biodiversity, with the potential to replace labour-intensive benthic macroinvertebrate-based freshwater quality assessments, such as SASS.     

Derivation of Population-Level Ecological Remedial Action Objectives: Tualatin River Case Study

In 1997, Oregon enacted rules that define an unacceptable population-level risk as a >10% chance of >20% of the total local population receiving an exposure greater than the toxicity reference value. This rule applies to populations of plants and animals not listed as threatened or endangered. An operational procedure was developed to perform such population-level ecological risk assessments. This case study describes how this procedure was used to develop site-specific groundwater remedial action objectives for resident aquatic populations at a site in Northwest Oregon, where an upland petroleum pipeline released gasoline-range hydrocarbons (TPH-G) into soils and groundwater immediately upgradient of the Tualatin River. With an interim response in place, the goal was to proactively establish a remedial action objective that would equate to an acceptable risk level for populations of aquatic receptors potentially threatened by future groundwater discharges to the river. Approximately 10 and 32% dilutions of the water-soluble fraction of pure product produced an acceptable risk level for zooplankton and forage fish populations, respectively. The proposed population-level remedial action objective, based on zooplankton as the most sensitive receptor, was a TPH-G groundwater concentration of 17.4?mg/L.     

Assessment of streams of the eastern United States using a periphyton index of biotic integrity

Benthic algae were collected from 272 eastern United States streams and rivers and analyzed for diatom species richness and dominance, the relative abundance of acidobiontic, eutraphentic, and motile diatoms, standing crops of chlorophyll and biomass, and alkaline phosphatase activity. These data were used to calculate a periphyton index of biotic integrity (PIBI), and values of the index were compared among reference, moderately impacted, and disturbed streams. The level of disturbance was based on stream chemistry, riparian disturbance, or a combined classification. Analyses of variance showed that PIBI was significantly higher in reference streams for all classifications. The PIBI and its metrics were correlated with many of the chemistry and habitat variables, and canonical correlation analysis revealed three significant environmental gradients which extracted 84% of the variance in the PIBI and its metrics. We used the mean 75th, 25th, and 5th percentile scores from the reference sites to set thresholds for excellent, good, fair, or poor condition. Applying these criteria to the cumulative distribution of total stream length in the region, we found that 4.3% of the stream length was in excellent condition; 20.8% in good condition; 56.4% in fair condition; and 18.5% in poor condition. The sensitivity of the PIBI and its component metrics to environmental stressors supports the use of this index for monitoring ecological conditions in streams in the eastern United States and as a tool to aid in diagnosing the causes of their impairment.     

Analysis of benthic macroinvertebrates,biological water quality and conservation value of a tropical river and UNESCO‐protected environment

Despite the growing awareness in freshwater conservation, and the sociocultural significance of the Osun River in the designation of the Osun‐Osogbo Sacred Grove as a UNESCO World Heritage Site, there is dearth of information on the biological water quality and conservation value of the river. In this study, the conservation value and biological water quality of the river which defines a UNESCO protected environment are assessed. Benthic macroinvertebrates and physicochemical water condition were studied quarterly from June 2015 to March 2016. The river's naturalness was also measured based on habitat alteration, land use and hydrological modifications. A total of 27 macroinvertebrate taxa were recorded, and the fauna was dominated by the Ephemeroptera, Odonata and Trichoptera (EOT) group. Taxa richness and/or abundance of macroinvertebrates showed a significant inverse response to vegetation removal, farming, total suspended solids, flow velocity, nitrate and phosphate. There is a notable occurrence of Margaritifera margaritifera which is considered a flagship and umbrella species in the river. This study further reveals the natural property of the sacred grove in addition to its cultural property as a WHS; hence, it may be re‐considered as a WHS based on mixed properties.     

Associations Between Macroinvertebrates and <Emphasis Type="Italic">Paralemanea mexicana</Emphasis>, an Endemic Freshwater Red Alga from a Mountain River in Central Mexico

Macrophytes are common inhabitants of lotic environments and, depending on their morphological traits, possess adaptations that provide shelter to aquatic invertebrates against strong river flow and predators. They may also be used as a food source by macroinvertebrates. The main goal of this study was to determine the relationship between the red alga Paralemanea mexicana and its role as a shelter and/or food source for lotic macroinvertebrates. We also conducted research on the role of microhabitat and morphological variations of the alga in determining macroinvertebrate taxon abundance, diversity, and functional group composition in a high-current velocity river. Results showed that changes in cover and morphology of P. mexicana were mostly correlated with river current velocity, irradiance, and seasonal variation. In turn, these were related to changes in abundance and diversity of the associated macroinvertebrate community. In addition, six macroinvertebrate functional feeding groups were evaluated for associations with the red alga: filtering and gathering collectors, piercers, scrapers, herbivore shredders, and predators. The results showed that the Trichoptera Hydroptilidae genera Ochrotrichia and Metrichia use P. mexicana as a food source and case-building material. The Trichoptera Glossosomatidae Mortoniella uses the alga as a substrate. The biotic interactions between P. mexicana and associated macroinvertebrates reveal the importance of macrophytes as purveyors of substrate, as food and shelter for macroinvertebrates, and also as promoters of macroinvertebrate community diversity. In addition, it was shown that macroinvertebrate herbivory likely facilitates vegetative propagation of the red alga through increased release and germination of carpospores and new gametophytes.     

Geographic variation in mangrove flooding and accessibility for fishes and nektonic crustaceans

In the last decade, dozens of indices based on macroinvertebrates were developed to evaluate lotic ecosystems. In contrast, very few of these indices have been applied in lentic ecosystems. Natural wetlands in southern Brazil are increasingly threatened by the expansion of irrigated rice. The main objective of this study was to develop a multimetric index based on macroinvertebrates to evaluate the water quality of natural wetlands and rice fields in southern Brazil. Three samplings were carried out over the rice growth cycle in four conventional and four biodynamic rice fields, and four natural wetlands. The wetlands were considered as reference sites, and the conventional and biodynamic rice crops were considered as manipulated sites at different levels of degradation. Seven metrics were included in the final index after passing though sensitivity and correlation tests. The results indicated that our index has a power to detect a gradient of variation in water quality. Natural wetlands had the best water quality, biodynamic crops had intermediate water quality, and the conventional crops had the lowest water quality. We believe that development of this macroinvertebrate-based multimetric index of water quality could be an important tool for monitoring natural wetlands and rice crops in southern Brazil.     

Flow‐related disturbances in forested and agricultural rivers: influences on benthic macroinvertebrates

Flow disturbances and conversions of land‐use types are two major factors that influence river ecosystems. However, few studies have considered their interactions and separated their individual effects on aquatic organisms. Using monthly monitoring data from two streams with different land‐use types (i.e. forest and agriculture) in the subtropical Central China over three years, we accurately predicted the changes of macroinvertebrate communities under flood disturbances and land‐use type conversions. The dominant taxa and main community metrics significantly declined following flash floods. Several mayflies and chironomid had rapid rates of recovery, which could reach high abundance in three months after floods. And most of the community metrics recovered more rapidly in the forested river than that in the agricultural river. Stepwise multiple regression (SMR) models were used to investigate the relationships between biotic metrics and hydrological and temporal variables. For example, SMR revealed that floods reduced the stability of benthic communities, and the length of low flow period was of considerable importance to the recovery of the fauna. Two‐way ANOVA indicated that intra‐annual fluctuation had more (e.g. the total abundance and wet biomass), equal (e.g. total richness, EPT richness, percent EPT abundance, and Margalef index), or less (e.g. tolerant value) influence on macroinvertebrate communities than land‐use types. Consequently, the effects of floods on macroinvertebrates should be taken into account when macroinvertebrates are used as indicators for assessing river ecosystem. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Assessing effects of water abstraction on fish assemblages in Mediterranean streams

1. Water abstraction strongly affects streams in arid and semiarid ecosystems, particularly where there is a Mediterranean climate. Excessive abstraction reduces the availability of water for human uses downstream and impairs the capacity of streams to support native biota. 2. We investigated the flow regime and related variables in six river basins of the Iberian Peninsula and show that they have been strongly altered, with declining flows (autoregressive models) and groundwater levels during the 20th century. These streams had lower flows and more frequent droughts than predicted by the official hydrological model used in this region. Three of these rivers were sometimes dry, whereas there were predicted by the model to be permanently flowing. Meanwhile, there has been no decrease in annual precipitation. 3. We also investigated the fish assemblage of a stream in one of these river basins (Tordera) for 6 years and show that sites more affected by water abstraction display significant differences in four fish metrics (catch per unit effort, number of benthic species, number of intolerant species and proportional abundance of intolerant individuals) commonly used to assess the biotic condition of streams. 4. We discuss the utility of these metrics in assessing impacts of water abstraction and point out the need for detailed characterisation of the natural flow regime (and hence drought events) prior to the application of biotic indices in streams severely affected by water abstraction. In particular, in cases of artificially dry streams, it is more appropriate for regulatory agencies to assign index scores that reflect biotic degradation than to assign ‘missing’ scores, as is presently customary in assessments of Iberian streams.     

Taxonomic Resolution and Quantification of Freshwater Macroinvertebrate Samples from an Australian Dryland River: The Benefits and Costs of Using Species Abundance Data

In studies using macroinvertebrates as indicators for monitoring rivers and streams, species level identifications in comparison with lower resolution identifications can have greater information content and result in more reliable site classifications and better capacity to discriminate between sites, yet many such programmes identify specimens to the resolution of family rather than species. This is often because it is cheaper to obtain family level data than species level data. Choice of appropriate taxonomic resolution is a compromise between the cost of obtaining data at high taxonomic resolutions and the loss of information at lower resolutions. Optimum taxonomic resolution should be determined by the information required to address programme objectives. Costs saved in identifying macroinvertebrates to family level may not be justified if family level data can not give the answers required and expending the extra cost to obtain species level data may not be warranted if cheaper family level data retains sufficient information to meet objectives. We investigated the influence of taxonomic resolution and sample quantification (abundance vs. presence/absence) on the representation of aquatic macroinvertebrate species assemblage patterns and species richness estimates. The study was conducted in a physically harsh dryland river system (Condamine-Balonne River system, located in south-western Queensland, Australia), characterised by low macroinvertebrate diversity. Our 29 study sites covered a wide geographic range and a diversity of lotic conditions and this was reflected by differences between sites in macroinvertebrate assemblage composition and richness. The usefulness of expending the extra cost necessary to identify macroinvertebrates to species was quantified via the benefits this higher resolution data offered in its capacity to discriminate between sites and give accurate estimates of site species richness. We found that very little information (<6%) was lost by identifying taxa to family (or genus), as opposed to species, and that quantifying the abundance of taxa provided greater resolution for pattern interpretation than simply noting their presence/absence. Species richness was very well represented by genus, family and order richness, so that each of these could be used as surrogates of species richness if, for example, surveying to identify diversity hot-spots. It is suggested that sharing of common ecological responses among species within higher taxonomic units is the most plausible mechanism for the results. Based on a cost/benefit analysis, family level abundance data is recommended as the best resolution for resolving patterns in macroinvertebrate assemblages in this system. The relevance of these findings are discussed in the context of other low diversity, harsh, dryland river systems.     

Application of clustering techniques for the characterization of macroinvertebrate communities to support river restoration management

The European Water Framework Directive prescribes that the development of a river assessment system should be based on an ecological typology taking the biological reference conditions of each river type as a starting point. Aside from this assessment, water managers responsible for river restoration actions also need to know the steering environmental factors to meet these reference conditions for biological communities in each ecological river type. As such, an ecological typology based on biological communities is a necessity for efficient river management. In this study, different clustering techniques including the Sørensen similarity ratio, ordination analysis and self-organizing maps were applied to come to an ecological classification of a river. For this purpose, a series of sites within the Zwalm river basin (Flanders, Belgium) were monitored. These river sites were then characterized in terms of biotic (macroinvertebrates), physical–chemical and habitat variables. The cluster analysis resulted in a series of characteristic biotic communities that are found under certain environmental conditions, natural as well as human-influenced. The use of multiple clustering techniques can be of advantage to draw more straightforward and robust conclusions with regard to the ecological classification of river sites. The application of the clustering techniques on the Zwalm river basin, allowed for distinguishing five mutually isolated clusters, characterized by their natural typology and their pollution status. On the basis of this study, one may conclude that river management could benefit from the use of clustering methods for the interpretation of large quantities of data. Furthermore, the clustering results might enable the development of a cenotypology useful for efficiently steering river restoration and enabling river managers to meet a good ecological status in most of the rivers as set by the European Water Framework Directive.     

The use of benthic macroinvertebrate families for river quality assessment in Lithuania

The aim of this study was to evaluate the influence of environmental factors on the distribution of macroinvertebrate taxa in different sized lowland Lithuanian rivers. A secondary aim was to assess ecological river quality and to determine the most suitable biotic index. A final aim was to determine the most appropriate macroinvertebrate families for river quality assessment in Lithuania. Species composition and quantitative characteristics of benthic macroinvertebrate communities have been investigated using standard kick-sampling method by a standard hand net in 24 different river sites in spring. Physical and chemical environmental parameters were measured in the same study site as the macroinvertebrate sampling. A total of 186 taxa representing 66 families or higher taxonomic ranks of benthic macroinvertebrates have been identified. Water temperature and current velocity influenced the highest number of ivestigated families. Seven of the most tolerant and eleven of the most sensitive macroinvertebrate taxa for hydrochemical parameters related with organic pollution were determined. The DSFI method was founded to be the best index for assessment of ecological status for Lithuanian rivers until more accurate estimation method will be created.     

Using the salinity preferences of benthic macroinvertebrates to classify running waters in brackish marshes in Germany

Marshland streams along European coastlines are typically located in the transition zone from limnic to brackish conditions. They constitute a distinct and important stream type within the German stream typology, which is predominantly characterised by tidal influence and salinity. According to the Water Framework Directive (WFD) the basis for the abiotic classification of European transitional and coastal waters is the ‘Venice System’ (Weber, M., 2005. Ergebnisse der Bestandsaufnahme 2004 zur Umsetzung der europäischen Wasserrahmenrichtlinie (WRRL) in den Küstengewässern Mecklenburg-Vorpommerns. Rostocker Meeresbiol. Beitr. 14, 7–15). However, the extreme spatial and temporal variability in salinity and tidal influence determines and controls the macroinvertebrate communities of marshland river and stream ecosystems and hampers the application of the ‘Venice System’. Earlier, purely biotic classifications of brackish waters typically classify different brackish water zones, each with a specific macroinvertebrate community, and often yield unsatisfactory results due to the extensively dynamic abiotic factors found in marshland streams. In practice, the permanent impact of tidal charge means that stable salinity zones do not exist. This effect can than be intensified by freshwater discharges after heavy rainfall or high tides in combination with strong winds that hinder discharge into the open sea. To overcome the restricted applicability of abiotic and biotic classification systems, we present a scoring system for marshland streams that combines the abiotic salinity classes of the ‘Venice System’ with the salinity preferences of the macroinvertebrate community. This proposal is based on literature data for macroinvertebrate salinity tolerances and preferences. According to the 137 references that were evaluated, 151 macroinvertebrate taxa were classified into six salinity groups. In a second step, we applied this scoring scheme to empirical data from two official quality assessment surveys. These surveys had been carried out in ten estuary tributaries of German marshland areas in Lower Saxony and Schleswig-Holstein in order to implement the WFD. Applying the scoring system to these data revealed a clear (and expected) gradient that was not expressed in the abiotic data. Thus we conclude that the biotic salinity preferences of benthic macroinvertebrates are a useful baseline metric for the ecological assessment of marshland streams and other transitional waters. Regional revision and adaptation of taxonomic salinity preferences would broaden the applicability of this assessment to transitional waters worldwide.     

Community structure or function: effects of environmental stress on benthic macroinvertebrates at different spatial scales

1. This study investigated the relation of benthic macroinvertebrates to environmental gradients in Central European lowland rivers. Taxonomic structure (taxa) and functional composition (metrics) were related to gradients at four different spatial scales (ecoregion, catchment, reach and site). The environmental variables at the catchment‐, reach‐ and site scales reflected the intensity of human impact: catchment and floodplain land use, riparian and floodplain degradation, flow regulation and river bank and bed modification. 2. Field surveys and GIS yielded 130 parameters characterising the hydromorphology and land use of 75 river sections in Sweden, the Netherlands, Germany and Poland. Two hundred and forty‐four macroinvertebrate taxa and 84 derived community metrics and biotic indices such as functional guilds, diversity and composition measures were included in the analysis. 3. Canonical Correspondence Analysis (CCA) and Redundancy Analysis (RDA) showed that hydromorphological and land use variables explained 11.4%, 22.1% and 15.8% of the taxa variance at the catchment (‘macro’), reach (‘meso’) and site (‘micro’) scales, respectively, compared with 14.9%, 33.2% and 21.5% of the variance associated with the derived metrics. Ecoregion and season accounted for 10.9% and 20.5% of the variance of the taxonomic structure and functional composition, respectively. 4. Partial CCA (pCCA) and RDA (pRDA) showed that the unique variance explained was slightly higher for taxa than for metrics. By contrast, the joint variance explained for metrics was much higher at all spatial scales and largest at the reach scale. Environmental variables explained 46.8% of metric variance and 32.4% of taxonomic structure. 5. Canonical Correspondence Analysis and RDA identified clear environmental gradients along the two main ordination axes, namely, land use and hydromorphological degradation. The impact of catchment land use on benthic macroinvertebrates was mainly revealed by the proportion of urban areas. At the reach scale, riparian and floodplain attributes (bank fixation, riparian wooded vegetation, shading) and the proportion of large woody debris were strong predictors of the taxonomic structure and functional composition of benthic macroinvertebrates. At the site scale, artificial substrata indicated human impact, particularly the proportion of macro‐ and mesolithal used for bank enforcement (rip–rap). 6. Our study revealed the importance of benthic macroinvertebrate functional measures (functional guilds, composition and abundance measures, sensitivity and tolerance measures, diversity measures) for detecting the impact of hydromorphological stress at different spatial scales.     

A study of terrestrial and aerial macroinvertebrates on river banks and their contribution to drifting fauna and salmonid diets in a Scottish catchment

Macroinvertebrates of terrestrial and aerial origin were examined on the river banks, in the drifting community and in the stomach contents of salmonids at seven stream sites within the river Nethy catchment in Scotland over a 12 month period. Differences between sites (which varied from moorland to forest), had some influence on the taxonomic composition and diversity of riparian macroinvertebrates but not on the proportion of terrestrial and aerial organisms in the drift or in salmonid guts. The abundances of terrestrial and aerial organisms collected on the river banks and in the drift were not related to the combination of riparian vegetation and altitude. The abundance on the river banks of terrestrial and aerial macroinvertebrates, particularly those possessing wings, varied seasonally and was positively correlated with temperature. Terrestrial and aerial prey contributed up to 86% of the salmonid diet. Organisms most abundant on the river banks were not always the predominant organisms in the drift or those selected by salmonids. This study concludes that it is necessary to examine the riparian and benthic macroinvertebrates (the original prey sources) and the drift (as the actual source of salmonid forays) directly to elucidate salmonid trophic pathways.     

Response of American dippers (Cinclus mexicanus) to variation in stream water quality

1. Semi‐aquatic birds may be sensitive to altered water quality. While avian species are not used in the bioassessment of streams, they may complement the more common use of benthic macroinvertebrates and fish. We estimated the extent to which water quality can predict attributes of the populations of one common semi‐aquatic bird, the American dipper (Cinclus mexicanus). 2. First, we estimated dipper presence/absence in relation to water quality as measured by a multimetric assessment index and individual bioassessment metrics. Second, we estimated dipper territory area and reproductive success in response to variation in water quality. We studied the diet, territory area and fecundity of dippers and sampled benthic macroinvertebrates, water chemistry and physical variables at 32 sites with and 17 sites without nesting dippers. 3. Dipper presence was only weakly related to chemical, physical and commonly recorded bioassessment metrics such as per cent Ephemeroptera, Plecoptera and Trichoptera (%EPT). Dippers were strongly related to the abundance of their common prey, Drunella and Heptageniidae, which are only a small component of the commonly recorded bioassessment metrics. The variances in territory area and reproductive success were weakly predicted by water quality variables. 4. Dipper presence reflected disturbance as measured by their common prey, showing that lower abundance of these stream invertebrates affected this semi‐aquatic bird. We suggest dipper presence/absence might be used in multimetric indices of biotic integrity for the bioassessment of streams.     

Predicting changes in the distribution and abundance of species under environmental change

Environmental changes are expected to alter both the distribution and the abundance of organisms. A disproportionate amount of past work has focused on distribution only, either documenting historical range shifts or predicting future occurrence patterns. However, simultaneous predictions of abundance and distribution across landscapes would be far more useful. To critically assess which approaches represent advances towards the goal of joint predictions of abundance and distribution, we review recent work on changing distributions and on effects of environmental drivers on single populations. Several methods have been used to predict changing distributions. Some of these can be easily modified to also predict abundance, but others cannot. In parallel, demographers have developed a much better understanding of how changing abiotic and biotic drivers will influence growth rate and abundance in single populations. However, this demographic work has rarely taken a landscape perspective and has largely ignored the effects of intraspecific density. We advocate a synthetic approach in which population models accounting for both density dependence and effects of environmental drivers are used to make integrated predictions of equilibrium abundance and distribution across entire landscapes. Such predictions would constitute an important step forward in assessing the ecological consequences of environmental changes.