Development of the HKHbios: a new biotic score to assess the river quality in the Hindu Kush-Himalaya

Within the ASSESS-HKH project (Development of an Assessment System to Evaluate the Ecological Status of Rivers in the Hindu Kush-Himalayan (HKH) region—a research project funded by the European Union; contract number: INCO-CT-2005-003659) a benthic invertebrate-based scoring system (HKHbios; Hindu Kush-Himalayan biotic score) was developed. The development was based on multi-habitat samples from 198 sampling sites located in five ecoregions and five Asian countries (Bangladesh, Bhutan, India, Nepal and Pakistan) taken in two different seasons (pre- and post-monsoon). Environmental and biological screening data were used to select macro-invertebrates as indicators for the ecological river quality. Taxa scores were assigned based on the range and distribution patterns of taxa amongst different degrees of impact and on available autecological information. In total, 199 taxa were scored for the HKHbios, which is calculated a weighted average score per taxon (ASPT). The range of the index values under different degrees of stress was evaluated and a five-class quality assessment system was generated for each ecoregion. Correlation analysis between the HKHbios, 38 selected environmental parameters and complex PCA gradients were used to test the response of the HKHbios to different kinds of impact.     

Assessing river ecological quality using benthic macroinvertebrates in the Hindu Kush-Himalayan region

We developed a system for the assessment of ecological condition for rivers in the lower mountains and lowlands of the Hindu Kush-Himalayan region (Pakistan, India, Nepal, Bhutan, and Bangladesh). We used benthic invertebrates collected from 198 rivers, located in five different ecoregions and covering degradation gradients; samples were taken twice (pre-monsoon and post-monsoon) applying a multi-habitat sampling procedure. Out of 38 environmental parameters, we constructed complex principal component analysis (PCA) gradients, separately for the stressors organic pollution, eutrophication, floodplain land use, and hydromorphological degradation. Correlation analysis between invertebrate metrics and environmental parameters revealed those biological metrics that are most responsive to river deterioration. Redundant metrics were deleted, and the most robust metrics were selected. The range of the index values under reference conditions was defined, and a five-class river quality system was generated.     

Integrating and extending ecological river assessment: Concept and test with two restoration projects

While the number of river restoration projects is increasing, studies on their success or failure relative to expectations are still rare. Only a few decision support methodologies and integrative methods for evaluating the ecological status of rivers are used in river restoration projects, thereby limiting informed management decisions in restoration planning as well as success control. Moreover, studies quantifying river restoration effects are often based on the assessment of a single organism group, and the effects on terrestrial communities are often neglected. In addition, potential effects of water quality or hydrological degradation are often not considered for the evaluation of restoration projects.We used multi-attribute value theory to re-formulate an existing river assessment protocol and extend it to a more comprehensive, integrated ecological assessment program. We considered habitat conditions, water quality regarding nutrients, micropollutants and heavy metals, and five instream and terrestrial organism groups (fish, benthic invertebrates, aquatic vegetation, ground beetles and riparian vegetation). The physical, chemical and biological states of the rivers were assessed separately and combined to value the overall ecological state.The assessment procedure was then applied to restored and unrestored sites at two Swiss rivers to test its feasibility in quantifying the effect of river restoration. Uncertainty in observations was taken into account and propagated through the assessment framework to evaluate the significance of differences between the ecological states of restored and unrestored reaches. In the restored sites, we measured a higher width variability of the river, as well as a higher width of the riparian zone and a higher richness of organism groups. According to the ecological assessment, the river morphology and the biological states were significantly better at the restored sites, with the largest differences detected for ground beetles and fish communities, followed by benthic invertebrates and riparian vegetation. The state of the aquatic vegetation was slightly lower at the restored sites. According to our assessment, the presence of invasive plant species counteracted the potential ecological gain. Water quality could be a causal factor contributing to the absence of larger improvements.Overall, we found significantly better biological and physical states, and integrated ecological states at the restored sites. Even in the absence of comprehensive before-after data, based on the similarity of the reaches before restoration and mechanistic biological knowledge, this can be safely interpreted as a causal consequence of restoration. An integrative perspective across aquatic and riparian organism groups was important to assess the biological effects, because organism groups responded differently to restoration. In addition, the potential deteriorating effect of water quality demonstrates the importance of integrated planning for the reduction of morphological, water quality and hydrological degradation.     

Hydromorphological degradation impact on benthic invertebrates in large rivers in Slovenia

Large rivers are amongst the most degraded ecosystems. We studied a relationship between hydromorphological degradation and benthic invertebrates in large rivers in Slovenia. Five indices of the Slovenian hydromorphological assessment methodology were used to develop a HM stressor gradient. Natural type-specific habitat diversity was considered in the hydromorphological stressor gradient building and thus two hydromorphological types of large rivers were defined. CCA ordination with five HM indices and 315 benthic invertebrate taxa revealed variations in taxa response along the HM stressor gradient. First CCA axis species values were used to develop a taxon-specific river fauna value (Rf_i), whereas tolerance values (biplot scaling) were used to determine a hydromorphological indicative weight (HW_i). Rf_i, HW_i, and log₅ abundance classes were combined using weighted average approach to construct a River fauna index for large rivers (RFI_VR). Several additional benthic invertebrate-based metrics were also tested against the HQM. A Slovenian multimetric index for assessing the hydromorphological impact on benthic invertebrates in large rivers (SMEIH_VR) was constructed from the RFI_VR and a functional metric %akal + lithal + psammal taxa (scored taxa = 100%). The strong relationship between hydromorphological stressor gradient and SMEIH_VR index provides us with an effective assessment system and river management tool.     

Hyporheic invertebrates as bioindicators of ecological health in temporary rivers: A meta-analysis

Worldwide, many rivers cease flow and dry either naturally or owing to human activities such as water extraction. However, even when surface water is absent, diverse assemblages of aquatic invertebrates inhabit the saturated sediments below the river bed (hyporheic zone). In the absence of surface water or flow, biota of this zone may be sampled as an alternative to surface water-based ecological assessments. The potential of hyporheic invertebrates as ecological indicators of river health, however, is largely unexplored. We analysed hyporheic taxa lists from the international literature on temporary rivers to assess compositional similarity among broad-scale regions and sampling conditions, including the presence or absence of surface waters and flow, and the regional effect of hydrological phase (dry channel, non-flowing waters, surface flow) on richness. We hypothesised that if consistent patterns were found, then effects of human disturbances in temporary rivers may be assessable using hyporheic bioindicators. Assemblages differed geographically and by climate, but hydrological phase did not have a strong effect at the global scale. However, hyporheic assemblage composition within regions varied along a gradient of higher richness during wetter phases. This indicates that within geographic regions, hyporheic responses to surface drying are predictable and, by extension, hyporheic invertebrates are potentially useful ecological indicators of temporary river health. With many rivers now experiencing, or predicted to experience, lower flows and longer dry phases owing to climate change, the development of ecological assessment methods specific to flow intermittency is a priority. We advocate expanded monitoring of hyporheic zones in temporary rivers and recommend hyporheic invertebrates as potential bioindicators to complement surface water assessments.     

环境因子对河流底栖无脊椎动物群落结构的影响

底栖无脊椎动物是河流生态系统的重要组成部分,在物质循环和能量流动中是不可或缺的重要环节。其群落结构特点与河流环境因子密切相关,能较好地反映河流生态系统健康状况。综述了物理因子(底质、温度、水深、水流、洪水干扰等)、化学因子(溶氧量、p H值、磷、氮等)、生物因子(水生植物、竞争和捕食)、人为干扰(电站建设、城镇化等)和综合因子对河流底栖无脊椎动物群落结构的影响,并根据国内外研究现状指出水流、海拔和洪水干扰等环境因子对河流底栖无脊椎动物群落结构影响的研究较少或不足,对这些环境因子的研究应是今后河流生态学领域需要着力推进重要内容。深入研究和完善环境因子与底栖无脊椎动物群落结构的关系可为保护底栖无脊椎动物群落、流域水生态系统管理和受损河流生态系统修复提供更为全面的科学依据。     

Nutrient optima and tolerances of benthic invertebrates,the effects of taxonomic resolution and testing of selected metrics in lakes using an extensive European data base

A large dataset from 1,077 lakes in Finland, Ireland, Sweden and the United Kingdom was collated to analyse the relationship between nutrient status and occurrence of different taxa, as well as between total phosphorus or chlorophyll and commonly used macroinvertebrate metrics developed for river assessment. We found that most taxa were associated with mesotrophic conditions (sensu OECD). Species associated with oligotrophic status included Baetis rhodani, Gammarus lacustris and plecopteran larvae, a group commonly associated with low nutrient status also in rivers. Species tolerant of eutrophic conditions were the chironomid larvae (Chironomus plumosus and Cryptochironomus defectus); and two species of tubificids (Psammoryctides barbatus and Potamothrix hammoniensis). For a number of taxa the associations of benthic invertebrates with nutrient state reported in the literature were not supported by analysis of the REBECCA data. The analysis indicated a variable response of littoral macroinvertebrates to eutrophication pressure when using common metrics developed for macroinvertebrates in rivers. Several metrics showed significantly different responses in lakes with different alkalinity, justifying the use of alkalinity for typing water bodies. These significant responses suggest that benthic invertebrates may be a useful component for classification of ecological status in lakes. The low amount of variance explained by the regressions (<30%), however, suggests that further harmonisation of sampling methods, as well as statistically more robust assessment tools are needed to increase the comparability of datasets and to improve the precision in the dose–response relationships.     

Current and substrate preferences of benthic invertebrates in the rivers of the Hindu Kush-Himalayan region as indicators of hydromorphological degradation

The study introduces an approach to obtaining information about the preferences of benthic invertebrates for substrate and current velocity in a region with little prior knowledge of benthic invertebrates. These preferences are then used for river assessment. Substrate-specific sampling of 271 reference sites was conducted in lower mountainous and lowland areas of the Hindu Kush-Himalaya region. Statistical analysis revealed significant preferences for substrate type and current velocity for 50 taxa of Ephemeroptera, Plecoptera, Trichoptera, Coleoptera, Diptera, Odonata, Mollusca, and Oligochaeta. A 20-point system was developed to assign scores for substrate and current preferences. Scores from seven taxa of Ephemeroptera and Trichoptera revealed low ecological potential in response to habitat alteration. These data were used to develop four preference metrics. The Lithal metric is composed of 34 taxa with significant preferences for stony substrates (fine gravel to bedrock size). The Lithophile metric contains 21 taxa with strong statistical links to stony substrates, which were also found on other substrates. The Lithobiont metric consists of 13 taxa exclusively found on stones. The Lotic metric consists of 11 taxa with significant preferences for moderate-to-fast current velocities. Multi-habitat sampling was conducted at 181 sites reflecting a hydromorphological gradient. The Mann–Whitney U test and box-and-whisker plots were applied to test the relationship of the new metrics to hydromorphological stress. Of the four new metrics, the Lithal, Lithophile, and Lotic were able to detect impacts of hydromorphological degradation.     

Spatial autocorrelation of assemblages of benthic invertebrates and its relationship to environmental factors in two upland rivers in southeastern Australia

The nature of spatial autocorrelation of biota may reveal much about underlying ecological and biological factors responsible for producing those patterns, especially dispersal processes (drift, adult flight, etc.). We report here on assemblage‐level autocorrelation in the benthic‐invertebrate assemblages (retained in sieves of 300 µm mesh) of riffles in two adjacent, relatively pristine rivers in southeastern Victoria, Australia (40‐km reaches of the Wellington and Wonnangatta Rivers). These are related to patterns of autocorrelation in physical and catchment conditions (‘environmental variables’) in the vicinity of the sampling points. Both the invertebrate assemblages and environmental variables were autocorrelated at small scales (= 8 km) in the Wellington River in one of the sampling years (1996). Dissimilarities of invertebrate assemblages were correlated with dissimilarities of environmental variables in both sampling years (1996 and 1997) in that river. Environmental variables were autocorrelated in the Wonnangatta River, but this was not expressed as autocorrelation in the assemblages of invertebrates, which were not autocorrelated at any scale studied. Individual environmental variables showed different spatial patterns between the two rivers. These results suggest that individual rivers have their own idiosyncratic patterns and one cannot assume that even similar, geographically adjacent rivers will have the same patterns, which is a difficulty for ecological assessment and restoration.     

Odonates as indicators of the ecological integrity of the river corridor: Development and application of the Odonate River Index (ORI) in northern Italy

The assessment of the ecological conditions of rivers is crucial for their appropriate management and restoration. Bioindicators commonly used to evaluate the river status (i.e. diatoms, aquatic macrophytes, benthic macroinvertebrates and fish) detect alterations of water quality, but are not particularly sensitive to hydromorphological degradation, which is another relevant pressure in river systems. Furthermore, those bioindicators are usually applied only to flowing channels. We developed a new multimetric index, the Odonate River Index (ORI), to assess the conditions of the whole corridor in alluvial rivers. The ORI is a development of an evaluation system proposed in Austria, and based on the Odonate Habitat Index (OHI). Odonates were chosen as bioindicators for the ecological integrity of the river corridor, since this taxon provides information on the conditions of their aquatic breeding sites, as well as on the surrounding terrestrial areas, due to its amphibiotic life cycle. We used a case study of 18 reaches from six Italian Alpine rivers, characterized by different morphological conditions and level of human impact. Within each study reach, we selected four sites, both lotic and lentic sites. Dragonfly surveys consisted in field observation of adults, and collection of larvae and exuviae. To define the best sampling strategy, we compared the results of the ORI metrics obtained varying the input data by combining different sampling methods: the best compromise between effort and exhaustiveness was obtained coupling the observation of adults with the collection of exuviae. We found the ORI to be a robust and reliable tool to assess the status of the river corridor in a wide range of environmental conditions and river morphology, being particularly suitable to detect hydromorphological degradation and alterations of the structure of aquatic and riparian vegetation. We identified two limiting factors for the applicability of this index: low water temperatures of the main channel (i.e. mean annual value below 10 °C) and river reaches with no or scarce aquatic and riparian vegetation. In addition to the assessment of river conditions, the ORI could also be applied for monitoring the effects of river restoration actions.     

Linking organism groups – major results and conclusions from the STAR project

Here we summarize results of the EU funded research project STAR concerning the suitability of different organism groups (fish, benthic invertebrates, macrophytes, diatoms) for monitoring European rivers. In a general way, the suitability of the organism groups is classified by monitoring type, stress type, river type, temporal scale and taxonomic resolution. For example, although all organism groups are affected by acidification, the relatively low species richness of fish and macrophytes in small mountain streams makes these two groups less suitable, and, hence, we argue that benthic diatoms and/or invertebrates may be considered as more robust indicators. Similar, lines of reasoning are given for a number of stressor and stream types.     

Performance of bottom ramps to mitigate gravel habitat bottlenecks in a channelized lowland river

The long‐term performance of measures to restore in‐stream habitat in gravel bed rivers is uncertain in the presence of impoundments, land use pressures, and fine sediment inputs. The goal of this study was to evaluate the longer‐term performance of five bottom ramps, designed to facilitate fish passage, and constructed similarly to artificial riffles to provide compensatory gravel riverbed habitat for benthic invertebrates and lithophilic, coarse‐substrate‐preferring fish in a channelized lowland river. Bottom ramp age did not significantly influence habitat conditions indicated by a lack of correlations with the percentage of fine sediment less than 2 mm, the organic content of the substrate, and the years since construction. A significant decrease in the relative abundances of coarse‐substrate‐preferring benthic invertebrates corresponding to project construction age was found, but there were no significant differences in the density of rheophilic, fast‐flow‐preferring or lithophilic fish species among sites. This study presents substantial evidence that similarly constructed bottom ramps in comparable environmental settings provided sufficient habitat for sensitive benthic invertebrates and fish to be present for over 13 years. However, a sudden decrease in habitat suitability cannot be excluded in the long‐term if there is a fine sediment deposition threshold, which results in ramps becoming full. Nevertheless, bottom ramps are recommended as effective measures to enhance longitudinal connectivity, fish passage, and gravel habitat provision in channelized lowland rivers.     

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.     

Ecological research for the restoration and management of rivers and reservoirs in Japan

In Japan the River Law was amended in 1997 to expand the traditional roles of flood control and water supply in river management to include environmental conservation. Two major multidisciplinary research groups were also founded to address the environmental issues arising from the management of rivers and watershed areas in Japan. One called the River Ecology Research Group was formed in 1995 to search for an ideal dynamic state of rivers to be managed. Six case studies commenced involving measurements of natural and human impacts on representative rivers and their biota selected from different regions of the country. Restoration of natural rivers has also been attempted. The other, called the Watershed Ecology Research Group, was formed in 1998 to study the natural environment surrounding dams. It consists of four groups concerned with forest ecology in the headwaters, raptor management research, reservoir ecology, and flow regime research. The topics include modeling of regeneration dynamics of riparian forests, GIS mapping of endangered raptor habitats, developing measures to reduce eutrophication of reservoir water, and the use of biodiversity of benthic faunas as an indicator of environmental change in the downstream. In both groups, ecologists collaborate with engineers who are responsible for the river infrastructure, to predict future impacts and keep ecological perspectives for the maintenance of the healthy environment of rivers and reservoirs.     

Sediment–Water Surface Area Along Rivers: Water Column Versus Benthic

Aquatic ecosystems have two distinct zones: the water column and benthic zone. Although the benthic zone has received considerable attention, recent studies have found the water column capable of accounting for a majority of whole ecosystem processes in rivers. The relative role of these zones inevitably varies across a size continuum of rivers, from headwaters to large transcontinental systems. A fundamental question in aquatic science is where along this size continuum do ecosystem processes potentially shift from occurring largely in the benthic zone to largely in the water column? Sediment structures the physical template of the benthic and water column zones of rivers and the contact area between water and sediment mediates ecological, geochemical, and physical processes. High concentrations of suspended sediments are hypothesized to cause a shift from benthic to water column dominance in rivers. We developed an analytical model for the contact area between surface water and all sediment particles in benthic and water column volumes. The model was implemented with empirical data along the main stem of major US rivers. The ratio of water column to benthic sediment contact area scaled as a power function of watershed area. There was more sediment–water contact area in the water column than the benthic zone in rivers equal to or greater than 5th to 9th order depending on the river basin. This suggests material processing could be occurring largely in the water column in rivers greater than 5th order. However, dams and variation in discharge caused rivers to oscillate between water column and benthic dominance over time and space.     

The rivers Rhine and Meuse in The Netherlands: present state and signs of ecological recovery

The ecosystems of the rivers Rhine and Meuse have suffered drastic environmental changes, for example because of the regulation of the stream bed and the construction of weirs and dams. Furthermore, discharges of industrial and municipal waste water have caused the water quality of these rivers to deteriorate; this problem became acute in the sixties and seventies. Recently some chemical parameters of water quality have improved in the Rhine, and as a consequence some aquatic communities are showing signs of recovery after decades of severe degradation. This paper describes the present state of the aquatic communities in the Dutch part of the rivers Rhine and Meuse, using published observations on plankton, macrophytes, invertebrates, and fish. The sparse information on the food chain in these rivers is summarized. The main channels of the Rhine and Meuse are characterized by a dense plankton that develops rapidly in the nutrient-rich river waters. The stream beds, now dominated by wave-exposed sand and gravel, have a sparse fauna and flora. The river banks, mostly consolidated by blocks of stone, offer a substratum for numerous benthic organisms, particularly now that the water quality has improved. The floodplain waters and old river channels harbour a flora and fauna rich in species. The degree of water exchange with the river is crucial for the ecological development of the river and its backwaters. Today the freshwater tidal reaches of the rivers occupy a very restricted area, and only remnants of the previously abundant vegetation of rushes are found. Losses in the numbers of animal and plant species, notably those specific to rivers, are evident, but over the last 15 years several species have returned. Allochthonous species (exotics), including crustaceans and molluscs, have also settled in the Rhine and Meuse. Fish species characteristic of these rivers, such as river lamprey, sea trout, barbel, and flounder, have recently been observed in appreciable numbers. The Rhine Action Programme provides a framework for the large-scale rehabilitation of the Rhine. Experiments on re-stocking the Rhine with Atlantic salmon and on the ecological rehabilitation of floodplains are being carried out on the assumption that there will be a further reduction of the pollution load. A similar programme is required for the Meuse.     

Development of an Index of Trophic Completeness for benthic macroinvertebrate communities in flowing waters

The analysis of the trophic structure of benthic macroinvertebrate communities can be used in biological assessments of the condition of river ecosystems. Using the trophic, or functional approach, the Index of Trophic Completeness (ITC) was developed. The goal was to overcome the problems and drawbacks of using conventional diversity or biotic indices in biological assessments of rivers, such as limitation to distinct geographical regions or focus on species richness without regard for ecosystem functioning. Following an extensive review of the literature on the trophic characteristics of benthic macroinvertebrates, a large number of species (±300) were characterized according to a number of trophic criteria: plant:animal ratio in the diet, feeding mechanism, food size, food acquisition behaviour, and energy and substance transfers. On the basis of their trophic characteristics, the species could be divided into 12 trophic groups. After examination of data from geographically diverse rivers, it was concluded that any undisturbed riverine benthic macroinvertebrate community should be represented by members of each of these 12 trophic groups, with each group fulfilling a function in the benthic community. Being a community which plays a central role in the functioning of the aquatic ecosystem, the benthic invertebrates are expected to respond to disturbances to the hydrobiocoenose. The outcome of an ITC assessment is clearly presentable in the form of a pie graph with 12 wedges, each representing one of the 12 defined trophic groups. Functionally complete communities are represented by 12 wedges; a blank wedge indicates that a trophic group is not represented. This paper describes the preliminary developments in the ITC method, its potential as a biological assessment method in rivers in different geographical zones, and presents examples of trial mappings of Russian and European rivers. The application of the ITC to these rivers demonstrated the absence of ITC trophic groups at sites under the influence of anthropogenic activity.     

河流岸带湿地沉积物重金属分布对植被物种多样性和底栖动物群落特征的影响

河流岸带湿地栖息地完整性对河流水环境、水生态和水文的安全与健康具有重要意义,为探究河流岸带湿地表层沉积物重金属分布特征及其对植被和底栖动物的影响,对滦河干流上中下游河段表层沉积物、植物群落和底栖动物调查分析,采用生物毒性效应系数法和综合潜在生态风险指数法评价沉积物重金属污染特征,采用植被物种多样性指数和底栖动物完整性指数评价滦河植物和底栖动物群落特征,探究岸带湿地沉积物重金属空间分布与植被及底栖动物群落特征之间关系。结果表明,滦河表层沉积物总体呈清洁水平,但不同河段重金属空间分布差异较大,下游重金属生态危害系数和潜在生态风险指数高于上中游。湿地物种调查共识别维管束植物219种,大型无脊椎底栖动物105种,综合评价结果表明下游植物群落物种多样性和底栖动物群落完整性低于上中游。滦河下游岸带湿地沉积物重金属对生物群落具有生物毒性和潜在的生态风险,降低了植被物种多样性和底栖动物群落完整性。大型底栖动物完整性指数能够综合反映底栖动物群落结构特征变化,对河岸带湿地生态健康评价和监测具有重要意义。     

The effect of taxonomic resolution on the assessment of ecological water quality classes

Within the ecological assessment of running waters based on benthic macroinvertebrates different levels of taxonomic resolution (species, genus, family and higher) are in use. Although assessment systems are often developed with detailed data on species level, water managers and other end-users could like to use data on higher taxonomic levels to assess the ecological quality of a water body because of limited human or money resources. The question that arises is, if an assessment system built with species level data is also applicable using data with a higher taxonomic resolution. Within the AQEM project a multimetric assessment system was developed to evaluate the ecological quality classes (from bad (1) to high (5) ecological quality) of different stream types throughout Europe. The present study focuses on the question whether the resulting water quality class changes using the AQEM Assessment Software (AAS) with different taxonomic resolutions and if yes, how large the deviations of ecological quality classes from the original classes are and if the deviations are unidirectional. For analyses data from four Austrian and two Dutch stream types were used. It is demonstrated that the assignment of a site to an ecological quality class may change if different taxonomic levels are used. Deviations in both directions (higher/lower ecological quality class) were observed. In most cases the divergence was only one ecological quality class, but also larger deviations occasionally occurred. The causes of changes in the assessment were investigated by separately looking into the underlying metrics of the multimetric system. Some of the evaluated metrics rely on autecological information on species level and are simply not applicable on higher taxonomic levels. Other metrics worked on higher taxonomic levels as well and showed more or less good distinctions between ecological quality classes. It is concluded that the AQEM Assessment Software is not applicable if data on higher taxonomic levels are used. As the deviations were not unidirectional and ranged from one to three ecological quality classes, it is not possible to include a correction factor for using the software with higher taxonomic resolution data.     

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.