Impacts of invasion by <Emphasis Type="Italic">Dreissena polymorpha</Emphasis> (Pallas, 1771) on the performance of macroinvertebrate assessment tools for eutrophication pressure in lakes

Aquatic ecosystems are experiencing increasing disturbance from multiple stressors caused by anthropogenic activities. The potential for multiple stressors to modify each others’ impacts is not well understood. Legislation such as the EU Water Framework Directive (WFD) requires the development of tools to assess human impacts in aquatic systems that incorporate ecological elements, such as macroinvertebrates. Nutrient enrichment and invasive species are major threats to freshwater systems. The invasive zebra mussel Dreissena polymorpha is a conspicuous invader in freshwater aquatic systems in Europe and North America, and has been linked to drastic changes in macroinvertebrate communities and lake ecology. In 31 lake sites varying in nutrient pressure and in the presence or absence of D. polymorpha we tested three ecological quality assessment tools based on macroinvertebrate assemblages (% Sensitive Taxa to Total Phosphorus (TP), TP Score and Indicator Taxa Metric) and two basic ecological metrics. There were highly significant changes in macroinvertebrate diversity, structure, and composition associated with the invasion by D. polymorpha. While the three metrics performed consistently well in non-invaded systems, they lost explanatory power for eutrophication pressure in invaded systems. Our results suggest that metrics may need to be developed separately for invaded and non-invaded systems, and that the interaction between alien species and nutrient enrichment requires further investigation.     

Response of macroalgae and macroinvertebrates to anthropogenic disturbance gradients in rocky shores

The compliance of macroalgal and macroinvertebrate assemblages to anthropogenic disturbance gradients (e.g., nutrient enrichment) was investigated at intertidal rocky shores. Macroalgae and macroinvertebrates presented parallel behavior, both showing shifts in the communities’ structural variation along the gradients, in which an higher number of opportunistic species (and higher abundances) were found in more stressful sites (close to the disturbance source), in contrast to less disturbed sites (far from the disturbance source), which showed higher presence of more sensitive species (and higher abundance of several of them).The macroinvertebrate abundance and taxonomic composition, which are parameters required by the Water Framework Directive (WFD) to be included in tools for the ecological quality status assessment, responded to the disturbance gradient. Results suggest that the macroinvertebrate biological element might be considered an indicator of disturbance in intertidal rocky shores as good as the macroalgae, and therefore the development of a specific methodology based solely on benthic macroinvertebrates of rocky shores, presently a gap in the ecological quality status assessment for the WFD, seems feasible.     

Relationship of fish and macroinvertebrate communities in the mid-Atlantic uplands: Implications for integrated assessments

Indices developed for stream bioassessment are typically based on either fish or macroinvertebrate assemblages. These indices consist of metrics which subsume attributes of various species into aggregate measures reflecting community-level ecological responses to disturbance. However, little is known about the relationship between fish and macroinvertebrate metrics, or about how ecological health assessments are affected by assemblage-specific responses to disturbance. We used principal component analysis (PCA) and regression analysis of existing fish (n = 371) and macroinvertebrate (n = 442) stream bioassessment data from a multi-source dataset to determine broad scale, within-assemblage metric patterns, and to examine the intercorrelation of fish and macroinvertebrate metrics (n = 246) and their response to watershed area and land use/land cover gradients. Fish and macroinvertebrate metrics expressed as principal components (PCs) accounted for 72.4 and 85.4% of dataset variance, respectively, with PC-metric patterns reflecting aspects of stream impairment including water and habitat quality. Model components predicting fish metric response differed among fish PCs, with watershed area and macroinvertebrate metric response strongly correlated with the first fish PC, and remaining fish PC models consisting of watershed area, land use, and macroinvertebrate PCs. Correlation between fish and macroinvertebrate PCs, and models relating fish and macroinvertebrate PCs generally explained less variation (13–27%) than metric response models of fish (25–34%) and macroinvertebrates (8–38%) to watershed area and land use/land cover variables. Best-response models integrating fish and macroinvertebrate PCs, watershed area, and land use/land cover variables accounted for the greatest variation in fish PCs (32–50%) across sites. Because fish and macroinvertebrate metrics provide different information on ecological condition, integrated use of information from multiple groups may be appropriate when developing monitoring programs.     

A biotic index using the seagrass Posidonia oceanica (BiPo), to evaluate ecological status of coastal waters

The development of ecologically based indices that respond to disturbances in a predictable manner has been stressed by the EU Water Framework Directive. The seagrass Posidonia oceanica, given its ecological indicator characteristics, has been identified as one of the elements to determine ecological status under the EU Water Framework Directive. The purpose of this study is therefore to develop a biotic index based on P. oceanica (BiPo), focussing on: (i) the necessity of an index that may be applied over the largest geographical extent possible, (ii) the necessity of a tool for a baseline evaluation of P. oceanica status in the Mediterranean, (iii) the compliance with WFD requirements, (iv) the efficiency of the method in terms of reliability and cost. The BiPo index is developed on the basis of all P. oceanica monitoring data available in the western Mediterranean and on a standard assessment of anthropogenic pressures. The index metrics are selected and evaluated on the basis of this pressures assessment, and are subsequently integrated for the evaluation of ecological status. The index is then tested on 15 sites around Corsica (France). The results show that the BiPo well reflects meadow health status and ecological status. Furthermore it is reliable, standard and cost-effective, and can be applied to a wide array of management and conservation purposes.     

Among-habitat and Temporal Variability of Selected Macroinvertebrate Based Metrics in a Mediterranean Shallow Lake (NW Spain)

According to the European Water Framework Directive, waterbodies have to be classified on the basis of their ecological status using biological quality elements, such as macroinvertebrates. This needs to take into consideration the influence of natural variation (both spatial and temporal) of reference biological communities as this may obscure the effects caused by anthropogenic disturbance. We studied the influence of among-habitat and temporal (seasonal and interannual) changes on the macroinvertebrate communities of an Iberian shallow lake and the variability of 21 measures potentially useful for bioindication purposes. Two series of data were examined: (a) macroinvertebrate samples taken on four occasions over an annual cycle were used to assess the effects of seasonality and among-habitat variability; (b) macroinvertebrate samples collected in three consecutive summers were used to assess interannual variability. Coefficients of variation, expressed as percentage, were used to quantify the effect of among-habitat and temporal variability on the selected metrics. According to our results, % Insecta, Shannon–Wiener diversity index and the qualitative taxonomic metrics (measures based on number of taxa) were robust in terms of temporal (seasonal and interannual) and among-habitat variability. Abundance ratio and some metrics based on functional feeding groups were highly variable. Therefore, qualitative taxonomic metrics may be promising tools in biomonitoring programs of Mediterranean shallow lakes due to their comparatively low variability.     

A comparative approach of assessing ecological status in two coastal areas of Eastern Mediterranean

This work presents an assessment of the ecological quality status of two marine coastal areas in the Aegean Sea (Greece, Eastern Mediterranean) based on the benthic macroinvertebrate quality element. S. Evvoikos and Thessaloniki gulfs, two coastal areas subjected to slight and heavier anthropogenic pressures, were selected to test the biotic index Bentix developed for the assessment of the ecological status. Other ecological indicators, such as the Shannon diversity index (H′), the species richness (S) and the AMBI biotic index were also applied and evaluated comparatively. Faunistic data were also used to interpret results. The resulting classification was validated with the use of physicochemical parameters and pressure information. This work also provides an insight into the structure of the Bentix classification scheme within the scope of its use in Water Framework Directive (WFD) implementation.     

Comparing the sensitivity of diverse macroinvertebrate metrics to a multiple stressor gradient in Mediterranean streams and its influence on the assessment of ecological status

Biological indicators are increasingly being used as integrative measures of the ecosystem health in streams, particularly those using macroinvertebrate assemblage composition. Monitoring biological quality of rivers has not a long tradition in some Mediterranean European countries like Spain. Several macroinvertebrate metrics have been recently proposed to assess ecological status in Mediterranean streams, so it is necessary to compare the use of proposed biological quality metrics to select the most appropriate ones.In the present work, two classic richness metrics (total number of families and number of the Ephemeroptera, Plecoptera and Trichoptera families), three indices (IBMWP, IASPT and t-BMWQ) and two multimetric indices, recently proposed to be used in Mediterranean streams (ICM-9 and ICM-11a or IMMi-L), were compared by the analysis of the sensitivity of these metrics to a multiple stressor gradient which reflected the main pressures present in the study area. For this purpose, data from 193 sites sampled in spring (95 reference sites and 98 disturbed sites) belonging to five different Mediterranean stream types present in 35 basins were studied.The results showed that the adjusted regression coefficients (r²) for all seven metrics in the exponential regression models were higher than linear ones, thus indicating an exponential relationship between metrics and the environmental alteration. The two studied multimetric indices presented higher regression coefficients (r² = 0.590–0.669) than the three indices (r² = 0.524–0.574) and the two metrics (r² = 0.471–0.525), therefore showing a better response to a stressor gradient in Mediterranean streams. Within the multimetric indices group, ICM-11a showed the highest regression coefficients. Based on the results obtained, we suggest using the ICM-11a, apart from the IBMWP, to assess ecological status in Mediterranean streams.     

A fish-based index of biotic integrity for upstream brooks in Flanders (Belgium)

From 1994 to 2000, 154 sites belonging to the grayling and trout zones were used to develop a fish-based multimetric Index of Biotic Integrity (IBI) as a tool to assess upstream brooks in Flanders (Belgium). All sites had a slope of at least 3‰ and a maximum width of 4.5 m. Fish assemblages were surveyed by electrofishing. From 28 candidate metrics 9 metrics were selected using ecological criteria and statistical analyses. The IBI was defined as the average of these 9 metrics after scoring them as 1, 3 or 5 by a modified trisection method and five integrity classes were defined to comply with the European Water Framework Directive (WFD). The IBI was tested internally by comparison with habitat quality scores at sites. A similar comparison was done using an independent set of data from sites of known ecological quality. Our IBI clearly distinguished good sites from disturbed sites and heavily disturbed sites from moderately disturbed sites, thereby meeting the criteria imposed by the WFD.     

Efficient sampling methodologies for lake littoral invertebrates in compliance with the European Water Framework Directive

Lake shores are characterised by a high natural variability, which is increasingly threatened by a multitude of anthropogenic disturbances including morphological alterations to the littoral zone. The European Water Framework Directive (EU WFD) calls for the assessment of lake ecological status by monitoring biological quality elements including benthic macroinvertebrates. To identify cost- and time-efficient sampling strategies for routine lake monitoring, we sampled littoral invertebrates in 32 lakes located in different geographical regions in Europe. We compared the efficiency of two sampling methodologies, defined as habitat-specific and pooled composite sampling protocols. Benthic samples were collected from unmodified and morphologically altered shorelines. Variability within macroinvertebrate communities did not differ significantly between sampling protocols across alteration types, lake types and geographical regions. Community composition showed no significant differences between field composite samples and artificially generated composite samples, and correlation coefficients between macroinvertebrate metrics calculated with both methods and a predefined morphological stressor index were similar. We conclude that proportional composite sampling represents a time- and cost-efficient method for routine lake monitoring as requested under the EU WFD, and may be applied across various European geographical regions.     

Microbial and macroinvertebrate communities,but not leaf decomposition,change along a mining‐induced salinity gradient

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Freshwater diatom and macroinvertebrate diversity of coastal permanent ponds along a gradient of human impact in a Mediterranean eco-region

Mediterranean coastal areas are characterised by heavily transformed landscapes and an ever-increasing number of ponds are subjected to strong alterations. Although benthic diatoms and macroinvertebrates are widely used as indicators in freshwater ecosystems, little is still known about the diatom communities of lowland freshwater ponds in the Mediterranean region, and, furthermore, there are few macroinvertebrate-based methods to assess their ecological quality, especially in Italy. This article undertakes an analysis of benthic diatom and macroinvertebrate communities of permanent freshwater ponds, selected along a gradient of anthropogenic pressures, to identify community indicators (taxa and/or metrics) useful to evaluate the effect of human impacts. A series of 21 ponds were sampled along Tyrrhenian coast in central Italy. Five of these ponds, in a good conservations status and surrounded by woodland were selected as ‘reference sites’ for macroinvertebrates and epipelic diatoms. The remaining sixteen ponds were located in an agricultural landscape subject to different levels of human impact. The total number of macroinvertebrate taxa found in each pond was significantly higher in reference sites than in both the intermediate and heavily degraded ones, whereas the diatom species richness did not result in a good community variable to evaluate the pond ecological quality. The analysis revealed a substantial difference among the compositions of diatom communities between reference ponds and degraded ponds. The former were characterised by the presence of several species belonging to genera, such as Pinnularia sp., Eunotia sp., Stauroneis sp., Neidium sp., all of which were mostly absent from degraded ponds. Furthermore, the taxonomic richnesses of some macroinvetebrate groups (Odonata, Ephemeroptera, Trichoptera, Coleoptera), and taxa composition attributes of macroinvertebrate communities (total abundance, percentages of top three dominant taxa, percentages of Pleidae, Ancylidae, Hirudinea, Hydracarina) significantly correlated with variables linked with anthropogenic pressures. The results of the investigation suggested that diatoms tended more to reflect water chemistry through changes in community structure, whereas invertebrates responded to physical habitat changes primarily through changes in taxonomic richness. The methodologies developed for the analysis of freshwater benthic diatom and macroinvertebrate communities may have a considerable potential as a tool for assessing the ecological status of this type of water body, complying with the European Union Water Framework Directive 2000/60/EC. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16 May 2008     

Do Contaminants Originating from State-of-the-Art Treated Wastewater Impact the Ecological Quality of Surface Waters?

Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0–100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive.     

A tool to assess the ecological condition of tropical high Andean streams in Ecuador and Peru: The IMEERA index

The main objective of this study was to develop a highland Andean streams ecological assessment tool for managers to determine the biological quality in this broad area of South America. Sampling was conducted during the dry season at 123 sites in eight watersheds of high Andean streams from south of Peru to North of Ecuador. The sites were at elevations above 2000 m a.s.l., and ranged in anthropogenic disturbance from none or little (reference) to highly disturbed. Using the physicochemical, hydromorphological and aquatic macroinvertebrate assemblage attributes of the reference sites, two different elevation bioregions were identified (from 2000 to 3500 m a.s.l. and those sites at altitudes higher than 3500 m a.s.l.). Differences between these two bioregions were related to the change in altitude of the most relevant environmental factors, i.e., temperature, oxygen content of the water and the extent of forested vegetation in the basin and in the riparian zone. These features were paramount to having different macroinvertebrate assemblages as demonstrated by an MDS analysis of our data. Two versions of the multi-metric index IMEERA were developed (the acronym comes from the Spanish name ‘Índice Multimétrico del Estado Ecológico para Ríos Altoandinos’) that corresponded to the two bioregions. In the lower altitude bioregion (Bosque river type, IMEERA-B index), the pressure gradient was driven by the organic pollution and the hydromorphological degradation. While in the higher elevation bioregion (Páramo and Puna river types; IMEERA-P river type), the gradient was driven by the organic pollution and the habitat heterogeneity. The IMEERA B index includes six macroinvertebrate metrics using its richness, habit characteristics and tolerance/intolerance to disturbances (EPT taxa, % clingers, % climbers, intolerant taxa, ABI and % tolerant taxa). The IMEERA P index was calculated using four metrics corresponding to macroinvertebrate richness and its tolerance/intolerance to disturbances (total taxa, intolerant taxa, ABI and % tolerant taxa). The index was validated with a set of independent data from the headwaters of Guayllabamba River in Ecuador.     

A comparison of algal,macroinvertebrate, and fish assemblage indices for assessing low-level nutrient enrichment in wadeable Ozark streams

Biotic indices for algae, macroinvertebrates, and fish assemblages can be effective for monitoring stream enrichment, but little is known regarding the value of the three assemblages for detecting perturbance as a consequence of low-level nutrient enrichment. In the summer of 2006, we collected nutrient and biotic samples from 30 wadeable Ozark streams that spanned a nutrient-concentration gradient from reference to moderately enriched conditions. Seventy-three algal metrics, 62 macroinvertebrate metrics, and 60 fish metrics were evaluated for each of the three biotic indices. After a group of candidate metrics had been identified with multivariate analysis, correlation procedures and scatter plots were used to identify the four metrics having strongest relations to a nutrient index calculated from log transformed and normalized total nitrogen and total phosphorus concentrations. The four metrics selected for each of the three biotic indices were: algae—the relative abundance of most tolerant diatoms, the combined relative abundance of three species of Cymbella, mesosaprobic algae percent taxa richness, and the relative abundance of diatoms that are obligate nitrogen heterotrophs; macroinvertebrate—the relative abundance of intolerant organisms, Baetidae relative abundance, moderately tolerant taxa richness, and insect biomass; fish—herbivore and detritivore taxa richness, pool species relative abundance, fish catch per unit effort, and black bass (Micropterus spp.) relative abundance.All three biotic indices were negatively correlated to nutrient concentrations but the algal index had a higher correlation (rho = ?0.89) than did the macroinvertebrate and fish indices (rho = ?0.63 and ?0.58, respectively). Biotic index scores were lowest and nutrient concentrations were highest for streams with basins having the highest poultry and cattle production. Because of the availability of litter for fertilizer and associated increases in grass and hay production, cattle feeding capacity increases with poultry production. Studies are needed that address the synergistic effect of poultry and cattle production on Ozark streams in high production areas before ecological risks can be adequately addressed.     

Spatio-temporal variation of environmental variables and aquatic macroinvertebrate assemblages in Lake Nokoué, a RAMSAR site of Benin

Environmental characteristics and macroinvertebrate assemblages of Lake Nokoué (Benin) were investigated from September 2014 to July 2016. Seasonal and hydroclimatic changes, as well as anthropogenic activities were the overriding factors affecting environmental variables investigated. Analysis of macroinvertebrate community structure with several indices revealed a community structure changing across seasons and differing between the sites. Mollusca, Crustacea and Polychaeta were most abundant in the dry seasons, especially at sites close to the ocean, whereas Oligochaeta and Insecta (Diptera, Heteroptera, Coleoptera, Odonata and Ephemeroptera) were abundant in the wet seasons, especially during flood periods (short wet season) at the sites receiving fresh water and on roots of macrophytes. A redundancy analysis placed habitat suitability (temperature and macrophytes) and trophic status variables (NO₂^?, NO₃^?, conductivity and pH) as structuring drivers for macroinvertebrate assemblages. The current study demonstrates that spatial heterogeneity of macroinvertebrates of Lake Nokoue is related to the dynamics created by input of fresh water (wet seasons) or salt water (dry seasons), as well as spatial heterogeneity of anthropogenic activities (nutrients). It offers insights into the macroinvertebrate dynamics linked to the limnology of a West African lagoon, which could contribute to a better understanding of management and conservation measures.     

Effects of invasive benthic macroinvertebrates on assessment methods of the EU Water Frame Work Directive

The assessment of the ecological status of aquatic ecosystems for the implementation of the European Water Framework Directive is based on different methods, many of which include the study of macroinvertebrate organisms. We examined whether and how invasive species affect the calculation of metrics used for fresh water assessment utilizing data from different substrate types in the streams of Central Germany. In these streams, the proportion of macroinvertebrate invasives increased from a very low fraction of the community up to 75% of species, or 96% of individuals, within 15 years. The values of the German Saprobic Index (GSI, reflecting the degree of organic load) did not differ significantly between different substrate types or within the examined stream reaches. However, saprobic valences of the species recorded did differ between substrates and between localities. This obvious contradiction is caused by an abundance of exotic species all having a medium GSI index between 2.2 and 2.3. Moreover, the minimum total number of organisms required for this method cannot be reached for a large majority of the sites dominated by invasives making it impossible to use the GSI. Regarding distribution of zonation types, the proportion of metarhithral species is low, and it is even lower on hard substrates than it is on soft substrates. This contradicts the general assumption that dwellers preferring metarhithral reaches (=lower-trout region) will show an affinity for habitats with higher oxygen concentrations and stronger flow velocities, both appearing more on hard than on soft substrates. This latter contradiction results from the classification of the most abundant invasive species Potamopyrgus antipodarum, Dikerogammarus villosus, and Chelicorophium curvispinum in the AQEM taxa reference list. The metrics ‘locomotion type’ and ‘feeding type’ were also affected by the presence of invasive species. Possible options for overcoming these assessment problems are discussed.     

Effects of sampling and sub-sampling variation using the STAR-AQEM sampling protocol on the precision of macroinvertebrate metrics

As part of the extensive field sampling programme within the European Union STAR project, replicate macroinvertebrate samples were taken using the STAR-AQEM sampling method at each of 2–13 sites of varying ecological quality within each of 15 stream types spread over 12 countries throughout Europe. The STAR-AQEM method requires the sub-sampling and taxonomic identification of at least one-sixth of the sample and at least 700 individuals. Replicate sub-samples were also taken at most of these sites. Sub-sampling effects caused more than 50% of the overall variance between replicate samples values for 12 of the 27 macroinvertebrate metrics analysed and was generally greatest for metrics that depend on the number of taxa present. The sampling precision of each metric was estimated by the overall replicate sampling variance as a percentage P_samp of the total variance in metric values within a stream type. Average over all stream types, the three Saprobic indices had the lowest percentage sampling variances with median values of only 3–6%. Most of the metrics had typical replicate sampling variances of 8–18% of the total variability within a stream type; this gives rise to estimated rates of mis-classifying sites to ecological status class of between 22 and 55% with an average of about 40%. This suggests that the precision of such metrics based on the STAR-AQEM method is only sufficient to indicate gross changes in the ecological status of sites, but there will be considerable uncertainty in the assignment of sites to adjacent status classes. These estimates can be used to provide information on the effects of STAR-AQEM sampling variation on the expected uncertainty in multi-metric assessments of the ecological status of sites in the same or similar stream types, where only one sample has been taken at a point in time and thus there is no replication.     

Hydromorphological restoration of running waters: effects on benthic invertebrate assemblages

1. River restoration has received considerable attention, with much recent focus on restoring river hydromorphology to improve impoverished aquatic communities. However, we still lack a clear understanding of the response of aquatic biota to river restoration. 2. We studied the effects of hydromorphological restoration on benthic invertebrate assemblages in 25 river sites in Germany using standardised methods. Restoration efforts were primarily aimed to restore habitat heterogeneity; correspondingly, habitat diversity increased at most sites. 3. Similarity of benthic invertebrate assemblages between restored and unrestored river sections was low (mean similarity was 0.32 for Jaccard and 0.46 for Sørensen). Community‐based metrics, such as the percentage of Ephemeroptera, Plecoptera and Trichoptera taxa, also differed between restored and unrestored sections. 4. Only three of the 25 restored sections were classified as having ‘good ecological quality’ class according to the European Water Framework Directive criteria; hence, poor water quality is probably one factor impeding recolonisation. 5. Our results show that isolated restoration measures do not necessarily result in positive effects on aquatic biota and that better understanding of the interconnectedness within a catchment is required before we can adequately predict biotic responses to structural river restoration.