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.     

Impact of climatic variability on parameters used in typology and ecological quality assessment of surface waters—implications on the Water Framework Directive

In most cases the negative impacts of climate change to aquatic ecosystems cannot be mitigated by measures in the river basin management. Ignoring climate change by the Water Framework Directive may have strong implications for the typology and quality assessment systems used for water bodies. As a result of climate change, water bodies, especially those located near the type boundaries may change their type. Compared to typology characteristics, water quality parameters are even more labile and may be easily affected by climate change. The paper exemplifies that the anticipated deterioration of water quality within the time frame relevant for WFD implementation may be large enough to endanger the fulfillment of the set water quality objectives. The review of the river basin characterization every six years, as required by the WFD, might also include re-evaluation of reference conditions according to the changes observed at pristine reference sites. As a consequence, the restoration targets (i.e., the good ecological status) would also need to be evaluated periodically.     

A comparison of the European Water Framework Directive physical typology and RIVPACS-type models as alternative methods of establishing reference conditions for benthic macroinvertebrates

The EU Water Framework Directive requires European Union Member States to establish ‘type-specific biological reference conditions’ for streams and rivers. Types can be defined by using either a fixed typology (System-A), defined by ecoregions and categories of altitude, catchment area and geology, or by means of an alternative characterisation (System-B) that can use a variety of physical and chemical factors. Several European countries also have existing RIVPACS-type models that give site (rather than stream type) specific predictions of benthic macroinvertebrate communities. In this paper we compare the Water Framework Directive (WFD) System-A physical typology and three existing European multivariate RIVPACS-type models as alternative methods of establishing reference conditions. This work is carried out in Great Britain – using RIVPACS, Sweden – using SWEPAC_SRI and the Czech Republic – using PERLA. We found that in all three countries, all seasons and season combinations, and for all biotic indices tested, RIVPACS-type models were more effective (lower standard deviations of O/E ratios) than models based solely on the WFD System-A variables or null models (based on a single expectation for all sites). We also investigated the explanatory power of whole groups of WFD System-A variables and RIVPACS-type model variables, and the explanatory power of individual variables. We found that variables used in the RIVPACS-type models were often better correlates of macroinvertebrate community variation than the WFD System-A variables. We conclude that this is primarily because while the latter use very broad categories of map-derived variables, the former are based on continuous variables selected for their ecological significance.     

Evaluating the ecological status of rivers using an index of ecological distance: An application to diatom communities

Community structure changes with pollution or stress. In the Water Framework Directive, high ecological status through biological parameters is defined as a slight or minor deviation from the reference community, while the good status is defined as a small deviation.To assess the importance of this deviation, and then to measure the degradation of ecological status along a river, an index based on the concept of “ecological distance” between species was created and called ecological distance index (EDI). It was tested on diatom data from a pilot watershed (the Garonne river basin, South-West France).The results show a good correlation between the EDI and the IPS (Indice de Pollusensibilité Spécifique – specific pollusensitivity index – a diatom-based biotic index) ecological ratios, which means first that the EDI is a valuable indicator of ecological status, and that it can account for ecoregional specificities. This index can be applied to any communities (macro-invertebrates, fish, etc.), since: (i) typical reference communities are found for each river type; (ii) species are characterised then ranked by pollution sensitivity values.     

The Reference Index Method for the Macrophyte‐BasedAssessment of Rivers – a Contribution to the Implementationof the European Water Framework Directive in Germany

The European Water Framework Directive requires ecological status classification and monitoring of surface and ground waters using biological indicators. To act as a component of the “Macrophytes and Phytobenthos” biological quality element, as demanded by the Directive, a macrophyte‐based assessment system was developed for application in river site types in Germany. Macrophyte abundance data were collected from 262 sites in 202 rivers. Seven biocoenotic river site types were established using differences in characteristic macrophyte communities reflecting ecoregion, channel width, water depth, current velocity, water hardness, and ground water influence. For four of these river site types, a macrophyte assessment system was developed, for the remaining three river site types data were insufficient for developing an assessment system. Ecological status classification of river sites is based on the calculation of a Reference Index value, in some cases supplemented by additional vegetation criteria. The Reference Index quantifies the deviation of species composition and abundance from reference conditions and classifies sites as one of the five possible ecological quality classes specified in the Directive. The assessment of long river stretches with changing river site types along its course is discussed based on an example from the Forstinninger Sempt River, southeast Germany. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Relationships among biological elements (macrophytes, macroinvertebrates and ichthyofauna) for different core river types across Europe at two different spatial scales

The objective of this study was to evaluate differences in correlations among Biological Elements and environmental parameters for different river types, analysed at two different spatial scales. A total of 82 sites, with at least good ecological status, were sampled across Europe, representing three core river types: Mountain rivers (26 sites); Lowland rivers (29 sites) and Mediterranean rivers (17 sites). At each site samples of macrophytes, macroinvertebrates and fishes were taken during spring, following the methodological procedures established by the European STAR project. Environmental parameters were also recorded, based on a site protocol developed by the European projects AQEM and STAR. Environmental parameters were divided into three categories: aquatic habitats (mesohabitat scale), global features (reach scale) and obligatory typology parameters of Water Framework Directive (WFD) (geographical scale). Data were analysed to evaluate at the two scales, first, relationships among biological elements, and second, relationships between biological elements and environmental parameters. Within each river type, correlation matrices (Bray–Curtis distance) were calculated separately for each biological element and for each category of environmental parameters. All biological elements were correlated (p<0.01) to the larger spatial scale: macrophytes and macroinvertebrates are more correlated in lowland and mountain rivers, while in Mediterranean rivers, fish and macrophytes presented higher correlations. These links tend to be consistent for different spatial scales, except if they are weak on a larger regional scale, obligatory parameters of WFD were, in most cases, significantly correlated with the three biological communities (p<0.05). Results at different spatial scales supported the hierarchical theory of river formation. Reach and mesohabitat environmental parameters tend to explain aquatic communities at a lower spatial scale, while geographical parameters tend to explain the communities at a major spatial scale.     

Using diatom life-forms and ecological guilds to assess organic pollution and trophic level in rivers: a case study of rivers in south-eastern France

The European Union’s Water Framework Directive has set a target of achieving good ecological status for all aquatic environments in Europe by 2015. In order to determine the quality of aquatic environments, biological indicators such as diatoms are often used. However, biotic diatom indices can be difficult and time consuming to use because of complexity of species determination. We investigated whether the biological traits of diatoms in rivers (life-forms, size classes and ecological guilds) could be used to assess organic pollution and trophic level. We worked on a data set comprising 315 diatom species, determined at 328 river stations of south-east France and a variety of parameters. The abundances of some biological traits differed significantly between the different organic pollution and trophic levels, particularly stalked diatoms, and the motile and low-profile guilds.     

Restoration of the Upper Main and Rodach rivers - The success and its measurement

Large-scale restoration of streams and rivers is a mandatory prerequisite for the implementation of the European Water Framework Directive (WFD) to reach good ecological status of water bodies. This contribution analyzes the success of the largest river restoration in Germany at the Upper Main. Sections with a length of more than 18 km were restored between 1990 and 2008, including re-connection of former oxbow-lakes, multiple-channelling, and establishment of wide riparian buffer zones.Measuring the success of restoration by means of a multimetric assessment system, we found a clear success of restoration indicated by the status of hydromorphology and by the biological parameters, including macroinvertebrates, fishes, and macrophytes. Unlike non-restored reaches, the restored reaches attained a good ecological status. As such, the restoration of the Upper Main is shown to be a pilot project for the implementation of the WFD on a large scale.     

Bryophyte communities of Mediterranean Europe: a first approach to model their potential distribution in highly seasonal rivers

Mediterranean watercourses are among the most threatened ecosystems worldwide, being increasingly important to understand environmental drivers of biotic assemblages. Our aim was to provide a comprehensive picture of bryophyte communities in Mediterranean rivers and to determine the environmental factors that influence their distribution. We used floristic data collected for inter-calibration purposes under the European Water Framework Directive and River Habitat Survey, from 474 river reaches in six countries of the European Mediterranean basin. We analysed data through classification, ordination and environmental niche modelling techniques, and classified taxa according to biogeographic and aquatic habitat frameworks developed specifically for bryophytes. These analyses revealed four types of communities influenced by spatio-temporal precipitation patterns, altitude and water chemistry factors, most notably calcium and manganese. Community types are compositionally differentiated, although they share some core taxa and show an overall tendency to have several temperate and exclusively aquatic taxa despite the intermittent nature of water flow in highly seasonal Mediterranean rivers. The modelling approach can be improved at a more local scale when more bryological data and higher-resolution environmental information become available. Given future scenarios of climate change and human alteration of hydrological regimes, broader scales studies are needed to monitor shifts in bryophyte communities.     

Ability of invertebrate indices to assess ecological condition on intertidal rocky shores

The implementation of directives such as the European Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) has promoted the development of several tools and methods for assessing the ecological health of marine ecosystems. Within the scope of the WFD and in terms of rocky shores, several multimetric tools were developed based on the macroalgae biological quality element (BQE), in addition to those based on macroinvertebrates.The WFD requires member states to assess each BQE separately. The present work aimed to test the ability of ecological indices to distinguish sites within anthropogenic disturbance gradients caused by organic enrichment, using macroinvertebrate communities on intertidal rocky shores. Owing to the lack of more specific indices (for rocky shore), indices based on abundance, diversity and/or taxonomic composition were selected from several widely used indices in ecological studies and/or developed for soft-bottom macroinvertebrate communities.Present findings reveal several indices based on diversity and/or taxonomic composition able to distinguish sites within the disturbance gradients, showing increasing quality from the site nearest the source of organic enrichment to that farthest from it, especially indices calculated using biomass data, and in the summer season. Such results open good perspectives for the use of intertidal macroinvertebrate communities from rocky shores, and also help add the perspective of this biological quality element in the ecological quality assessment of coastal waters.     

Ecological indicators for stream restoration success

Exploitation of freshwater resources is essential for sustenance of human existence and alteration of rivers, lakes and wetlands has facilitated economic development for centuries. Consequently, freshwater biodiversity is critically threatened, with stream ecosystems being the most heavily affected. To improve the status of freshwater habitats, e.g. in the context of the European Water Framework Directive and the US Clean Water Act, it is essential to implement the most effective restoration measures and identify the most suitable indicators for restoration success. Herein, several active and passive bioindication approaches are reviewed in light of existing legal frameworks, current targets and applicable implementation of river restoration. Such approaches should move from the use of single biological indicators to more holistic ecological indicators simultaneously addressing communities, multiple life stages and habitat properties such as water quality, substrate composition and stream channel morphology. The proposed Proceeding Chain of Restoration (PCoR) can enable the integration of natural scientific, political and socioeconomic dimensions for restoration of aquatic ecosystems and associated services. Generally, an analysis that combines target species-based active bioindication with community-based passive bioindication and multivariate statistics seems to be most suitable for a holistic evaluation of restoration success, as well as for the monitoring of stream ecosystem health. Since the response of biological communities to changing environmental conditions can differ between taxonomic groups and rivers, assessments at the ecosystem scale should include several levels of biological organisation. A stepwise evaluation of the primary factors inducing disturbance or degradation is needed to integrate increasing levels of complexity from water quality assessments to the evaluation of ecological function. The proposed PCoR can provide a step-by-step guide for restoration ecologists, comprising all planning steps from the determination of the conservation objectives to the use of ecological indicators in post-restoration monitoring.     

Macrophyte‐based assessment of lakes – a contribution to the implementation of the European Water Framework Directive in Germany

The European Water Framework Directive requires ecological status classification and monitoring of surface and ground water bodies using biological indicators. To fulfill the demands of the Directive, a macrophyte‐based assessment system was developed for application on four lake site types in Germany. Biological lake site types were established using differences in characteristic macrophyte communities, reflecting ecoregion, Ca²⁺ content, mixis and morphology. Ecological status classification of lake sites is based on macrophyte abundance along 275 transects in 95 natural German lakes and the calculation of a reference index value, in some cases supplemented by submerged vegetation data. The reference index quantifies the deviation of species composition and abundance from reference conditions and classifies sites to one of the five ecological quality classes specified in the Directive. Based on an example of Lake Chiemsee, Germany, the possibilities for a wholelake assessment are discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

River bioassessment and the preservation of threatened species: Towards acceptable biological quality criteria

A central objective of environmental management is to maintain biodiversity, including populations of threatened species. Freshwater ecosystems are increasingly assessed by their biotic properties, but whether the resulting classifications of biotic condition are sufficient to protect species with conservation status has received very little consideration. We used data from 225 reference and impacted river sites from Finland to examine whether the occurrence and abundance of threatened macroinvertebrate species (TS) are associated with a commonly used estimate of biological condition (Observed-to-Expected number of predicted taxa of macroinvertebrates or O/E-ratio of taxonomic completeness, based on a predictive model). We suggest that a minimal acceptable condition below which restoration is needed, equivalent to, e.g. ‘good’ ecological status described by the European Union Water Framework Directive, should also ensure the occurrence of TS populations. We therefore followed conventional procedures for condition assessment, and examined two classifications by using the 10th or 25th percentiles of a reference O/E-distribution as alternative upper boundaries for the acceptable condition. The number and abundance of TS, and occurrence of individual TS showed positive relationships with the O/E. However, particularly if the 10th percentile threshold was used, there were only few occurrences and low abundance of TS in the suggested ‘good’ condition. The results imply that conventional criteria for satisfactory condition may not be sufficient for preservation of threatened river macroinvertebrates. However, our approach could bring an objective, meaningful, and societally acceptable means for setting site quality criteria in freshwater assessment.     

The impact of hydromorphological restoration on river ecological status: a comparison of fish, benthic invertebrates, and macrophytes

The European Water Framework Directive (WFD) has led to an increase in hydromorphological restoration attempts in European rivers, but data on the ecological responses of rivers to these restoration attempts are scarce. We investigated the effects of 24 hydromorphological river restoration projects in Germany. We compared hydromorphological parameters and biological diversity of macroinvertebrates, fish, and macrophytes in restored reaches to nearby unrestored sections. We applied, for the first time, the WFD to assess the results of these restoration projects. While hydromorphology changed significantly in the restored sections, differences between restored and unrestored sections in terms of biological parameters were lower. Positive restoration effects were observed for fish (11 of 24 cases) only. Based on the synthesis of results from the different organism groups, only one of the 24 restored sections reached a “good” Ecological Quality Class as demanded by the WFD. Our results indicate that stressors other than hydromorphological degradation still affect the biota in restored sections. We emphasize the need for advanced restoration strategies based on catchment analyses considering water pollution, source populations, and dispersal capacities of sensitive species, and recommend the inclusion of additional parameters, including societal and stakeholder perspectives, in assessing the initial success of restoration projects.     

Macrophyte communities in unimpacted European streams: variability in assemblage patterns, abundance and diversity

Macrophytes are an important component of aquatic ecosystems and are used widely within the Water Framework Directive (WFD) to establish ecological quality. In the present paper we investigated macrophyte community structure, i.e., composition, richness and diversity measures in 60 unimpacted stream and river sites throughout Europe. The objectives were to describe assemblage patterns in different types of streams and to assess the variability in various structural and ecological metrics within these types to provide a basis for an evaluation of their suitability in ecological quality assessment. Macrophyte assemblage patterns varied considerably among the main stream types. Moving from small-sized, shallow mountain streams to medium-sized, lowland streams there was a clear transition in species richness, diversity and community structure. There was especially a shift from a predominance of species-poor mosses and communities dominated by liverwort in the small-sized, shallow mountain streams to more species-rich communities dominated by vascular plants in the medium-sized, lowland streams. The macrophyte communities responded to most of the features underlying the typological framework defined in WFD. The present interpretation of the WFD typology may not, however, be adequate for an evaluation of stream quality based on macrophytes. First and most important, by using this typology we may overlook an important community type, which is characteristic of small-sized, relatively steep-gradient streams that are an intermediate type between the small-sized, shallow mountain streams and the medium-sized, lowland streams. Second, the variability in most of the calculated metrics was slightly higher when using the pre-defined typology. The consistency of these results should be investigated by analysing a larger number of sites. Particularly the need of re-defining the typology to improve the ability to detect impacts on streams and rivers from macrophyte assemblage patterns should be investigated. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Assessing the Ecological Integrity of a Major Transboundary Mediterranean River Based on Environmental Habitat Variables and Benthic Macroinvertebrates (Aoos‐Vjose River,Greece‐Albania)

Ecological integrity has become a primary objective in monitoring programs of surface waters according to the European Water Framework Directive. For this reason we propose a scheme for assessing the ecological integrity of a major transboundary river, the Aoos‐Vjose (Greece‐Albania), by analysing the effects of physicochemical, hydromorphological and habitat structure variables on benthic macroinvertebrates. Benthos and water samples were obtained from 17 sites, during high and low flow season. Physical habitat structure was determined using the River Habitat Survey method. In all but one of the surveyed habitats no anthropogenic change was evident. Macrobenthos assemblages were mainly influenced by seasonality and river section, whereas the water quality index was negatively correlated to habitat modification. Consequently, a large part of the river is considered of high ecological integrity and as such it may be used as baseline information for the management of other major rivers in the eastern Mediterranean basin. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Efficiency and uncertainties in micro- and mesoscale habitat modelling in large rivers

Habitat modelling has become an increasingly important tool in river sciences to evaluate impacts on running waters and to predict the effects of river restoration in the context of the European Water Framework Directive which aims to reach a good ecological status by 2015. In a scaling framework like the River Scaling Concept, micro- and mesoscale habitat modelling hierarchically integrate point-/local-scale abiotic processes like grain sorting, initiation of sediment transport, bedform development and braiding with biological processes like spawning, daily and seasonal movements, feeding and shifting to refuge habitats. The paper, along with application results, shows that micro- and mesoscale habitat models are complementary especially for large river systems. Overall possibilities, restrictions and future development are discussed. Both rely on dynamic abiotic modelling as a basis as well as on biological data. In future, especially for large rivers, habitat modelling should be addressed on both scales (micro-/meso-) with the main focus on site-specific efficiencies (e.g. minimum efforts) and uncertainties (e.g. transferring suitability indices).