Assessing morphological degradation in running waters using Blackfly communities (Diptera, Simuliidae): Can habitat quality be predicted from land use?

Based on benthic macroinvertebrate samples from 57 sites of streams in the European Central Highlands (Ecoregion 9; Illies (1978). Limnofauna Europaea, Stuttgart), the composition and the abundance of Simuliid species were analysed in relation to hydromorphological and land use parameters. Sampling sites were located at two stream types differing in catchment geology, stream morphology and channel width. Land use data were taken from the official German information system for cartography and topography (ATKIS) and the German River Habitat Survey. Land use categories suitable to describe the sampling sites were ‘agricultural land’, ‘urban’ and near-natural areas. Hydromorphological parameters of the sites were recorded using the AQEM site protocol (AQEM Consortium (2002). Manual for the application of the AQEM system. A comprehensive method to assess European streams using benthic macroinvertebrates, developed for the purpose of the Water Framework Directive. EVK1-CT1999-00027, Version 1.0. Available via the Internet from www.aqem.de). Relevant parameters controlling Simuliid distribution in streams were the mineral substrates and the biotic microhabitats. Blackfly larvae and pupae were sampled at each site for 15 min. Statistical analysis was performed by CANOCO^® (Ter Braak & Smilauer (1997). CANOCO Version 4.5. Biometrics Plant Research International, Wageningen, The Netherlands) using redundancy analysis (RDA).

Our results show a stream type-specific composition of the Blackfly fauna. The analyses reveal sensitivity of the Simuliid species to morphological degradation, which is indicated by the shift in the longitudinal zonation of the Simuliid communities. Especially, Prosimulium hirtipes (Fries, 1824) and Simulium argyreatum Meigen, 1838 are typical representatives of headwater streams. While they seem to indicate undisturbed conditions of this stream type and react sensitively to the degradation of stream habitats, Simulium ornatum Meigen, 1818 and Simulium equinum (Linnaeus, 1758) are more tolerant to stream degradation.

On catchment scale, ‘% natural forest’ and ‘% agricultural land use’ illustrate the degree of degradation of the two selected stream types. ‘Average stream depth’ and ‘relation riffles/pools’ account for hydromorphological degradation reflected by Simuliid species on the smaller reach scale. The analysis of habitat quality revealed that ‘% woody debris’ represents an important parameter of morphological degradation reflected by the Blackfly community.     

Biological and hydromorphological integrity of the small urban stream

Biological and hydromorphological integrity of five reaches of the small urban stream were assessed. Because macroinvertebrate communities respond to both organic pollution and habitat change, impacts of both measures can be hardly separated. In our study on the urbanized small stream, an impact of organic pollution was excluded as all five sampling sites were assessed as moderately polluted. On the other hand differences in morphological degradation of banks and channel of selected sites enabled us to relate hydromorphological stress and biotic metrics and taxa. Physical habitat quality was assessed using River habitat survey (RHS) methodology. A downstream-upstream gradient of physical habitat degradation was observed and related to the macroinvertebrate community characteristics. Similarity analyses and biotic metrics were calculated and correlated with results of the RHS analyses. Composition of the macroinvertebrate assemblages did not follow the longitudinal pattern of habitat modification observed by the RHS analysis. However, some metrics corresponded well. Percentage of detritivores, percentage of Caenis luctuosa, number of individuals, percentage of EPT individuals were best predictors of changes in the physical habitat quality. However, the metric percentage of EPT individuals was negatively correlated to the habitat degradation, what is in contradiction with results from studies of other authors.     

Effects of sampling microhabitats with low coverage within the STAR/AQEM macroinvertebrate sampling protocol on stream assessment

In the STAR/AQEM protocol microhabitats covering less than 5% of the sampling area were neglected. Driven by an ongoing discussion on the importance of these underrepresented microhabitats we tested the influence of sampling them. We investigated 48 streams representing 14 different stream types from all over Germany. Macroinvertebrates of underrepresented microhabitats were sampled in addition to the STAR/AQEM protocol. To ensure the method remains feasible in routine monitoring programmes the total sampling and sorting effort of additional sampling was limited to 20 min. Particularly those taxa were picked, which were not recognised during the routine STAR/AQEM sorting.To identify the effect of additional sampling on stream assessment results, we calculated the stream type-specific Multimetric Index (MMI) with the “main” and the “main+additional” data for each sample. The mean and median difference in MMI values between “main” and “main+additional” samples was 0.02 and 0.01, respectively. In seven of 48 samples (14.6%) a different ecological quality class was calculated with the “main+additional” dataset. Regarding common metrics within the MMI as well as intercalibration metrics differences between “main” and “main+additional” samples were analysed. The values differed most in richness metrics (e.g., number of EPTCBO Taxa, number of Trichoptera Taxa). The results of the present study show that additional sampling of underrepresented microhabitats could alter multimetric assessment results.     

Pressure-specific and multiple pressure response of fish assemblages in European running waters

We classified homogenous river types across Europe and searched for fish metrics qualified to show responses to specific pressures (hydromorphological pressures or water quality pressures) vs. multiple pressures in these river types. We analysed fish taxa lists from 3105 sites in 16 ecoregions and 14 countries. Sites were pre-classified for 15 selected pressures to separate unimpacted from impacted sites. Hierarchical cluster analysis was used to split unimpacted sites into four homogenous river types based on species composition and geographical location. Classification trees were employed to predict associated river types for impacted sites with four environmental variables. We defined a set of 129 candidate fish metrics to select the best reacting metrics for each river type. The candidate metrics represented tolerances/intolerances of species associated with six metric types: habitat, migration, water quality sensitivity, reproduction, trophic level and biodiversity. The results showed that 17 uncorrelated metrics reacted to pressures in the four river types. Metrics responded specifically to water quality pressures and hydromorphological pressures in three river types and to multiple pressures in all river types. Four metrics associated with water quality sensitivity showed a significant reaction in up to three river types, whereas 13 metrics were specific to individual river types. Our results contribute to the better understanding of fish assemblage response to human pressures at a pan-European scale. The results are especially important for European river management and restoration, as it is necessary to uncover underlying processes and effects of human pressures on aquatic communities.     

Renaturalization of streams and rivers — the special importance of integrated ecological methods in measurement of success. An example from Saxony-Anhalt (Germany)

Since hydromorphology in about 80% of German streams and rivers is degraded to a high degree, increased efforts in hydromorphological renaturalization are necessary. A measurement of the success of the first realized projects shows that improvement in stream morphology has a remarkably positive influence on aquatic ecology. An example of a restored stretch of a lowland stream in Saxony-Anhalt is used to describe the possibilities of success measurement programs for improvement of poor renaturalization. Therefore, a combined morphological and hydrobiological approach was developed. An integrated ecological assessment is possible by using the multimetric index EQI_M (Ecological Quality Index using benthic Macroinvertebrates) and the GFI (German Fauna Index). The latter represents a tolerance measure to evaluate the hydromorphological status of a site by using certain taxa that indicate either positive or negative physical attributes. To consider the special characteristics of the stream in its landscape unit, specific reference conditions (‘Leitbild’) were defined for macroinvertebrate communities by sampling comparable but undisturbed streams in the same landscape unit. Only the combination of biological indices, hydromorphological mapping and comparison to the reference status allows for an expressive evaluation of renaturalization measures and precise conclusions for their improvement.     

Assessing streams in Germany with benthic invertebrates: Development of a multimetric invertebrate based assessment system

The main aim of the study was to develop a multimetric assessment system for macroinvertebrate communities of small and mid-sized streams in Germany in accordance with the Water Framework Directive of the European Union. The system should be applicable by water authorities, capable of distinguishing between different impacts, and specifically adapted to all types of small and mid-sized rivers in Germany. An assessment system has been developed consisting of two modules based on the established indices for saprobic degradation and acidity, and a third module covering general degradation. For the third module a new multimetric index (MMI) was developed and tested using preclassifications for stream hydromorphological degradation, land use and general impairment as impact measures. More information on sampling method, season and the type of dominating human impairment allowed to further analyse the index' capabilities and sensitivity. It performed well in all seasons and detected all types of impairment except acidity. The usefulness of the impact measures used in this study is discussed with regard to the development of a multimetric index. The comparison of the new index with other indices showed that it is especially sensitive in detecting macroinvertebrate community responses to hydromorphological degradation and pollution such as the German AQEM index, while IBI 12 and Renkonen's similarity more reflect general community shifts caused by any type of disturbance. The new assessment system will be proposed for future use by state agencies for nationwide monitoring in the context of the Water Framework Directive implementation.     

Ecological classification of macrophytes and phytobenthos for rivers in Germany according to the water framework directive

A new assessment system for macrophytes and phytobenthos in German rivers meeting the requirements of the Water Framework Directive (WFD) of the European Community is described. Biocoenotic types based on biological, chemical and hydromorphological data from over 200 river sites covering the main ecoregions, hydromorphological stream types and degradation forms have been defined. For developing a classification system the quality element macrophytes and phytobenthos was divided into three components: macrophytes, benthic diatoms and remaining phytobenthos. For macrophytes seven types including one subtype, for benthic diatoms 14 types including three subtypes and for the remaining phytobenthos five river types were identified. The benthic vegetation at reference condition was described for most of the river types. Degradation is characterised as deviation in benthic vegetation species composition and abundance from the reference biocoenosis. For classification in five ecological status classes, several metrics were developed and used in combination with existing indices. For some of the described river types additional investigations are necessary before a classification system can be developed.     

Macroinvertebrate assemblages in conditions of low-discharge streams of the Cerová vrchovina highland in Slovakia

Macroinvertebrate communities at 16 sites in Cerová vrchovina highland were sampled in 2000–2001 to analyze the influence of environmental factors on community structure with emphasis on Ephemeroptera, Plecoptera and Trichoptera (EPT). The extreme hydrological conditions of this area determine the macroinvertebrate community structure. Totally, 16 Ephemeroptera, 8 Plecoptera and 36 Trichoptera taxa were found. Predators of the families Perlidae, Perlodidae and Chloroperlidae (Plecoptera) were absent. The record of Protonemura aestiva is the second one in Slovakia. Ephemeroptera were represented mainly by rheophilous taxa. A rare lowland species Baetis tracheatus was found, known previously just from West Slovakia. Trichoptera were mainly represented by submontane rheophilous taxa. Species preferring low currents or backwaters from the family Limnephilidae were also recorded. Altitude and dissolved oxygen content were found to be the most important environmental variables determining the EPT community structure. Six types of streams were distinguished by the results of multivariate analysis, taxonomic composition and metric values. They belong to two main types: (1) EPT communities of the natural streams and (2) EPT communities of disturbed streams, where two types of stressor were identified–organic pollution and low discharge. A similarity between EPT communities of organically polluted streams and streams with very low flow was discovered. Values of biotic indices decreased in summer. The most diversified communities were found in the spring during higher water levels and better oxygen conditions.     

Reference conditions of German stream types analysed and revised with macroinvertebrate fauna

This study investigates reference conditions of German stream types using the top-down stream typology developed by Pottgiesser & Sommerhäuser (2004) and 264 macrozoobenthos samples selected as representing reference status. With the aid of discriminant and correlation analyses, the use of typological parameters is investigated as regards their relevancy and the study aims to show whether the metrics used in the newly developed type-specific indices (Böhmer et al. 2004b) reflect the reference conditions. The data cover 15 of the 24 German stream types. The use of stream size, of ecoregions as an indirect parameter for geographical altitude, and of the bottom substrate for the lowland stream types as typological factors can be confirmed, as can six stream types as separate and independent. As bottom substrate is an essential factor for the lowland stream types, their independency is at least probable. For the stream types of the lower mountain regions, a separation of siliceous and calcareous types seems not to be crucial for the bioassessment on metric level, while a new approach for and a possible splitting of the small streams in floodplains is recommended.     

Typology of streams in Germany based on benthic invertebrates: Ecoregions, zonation, geology and substrate

Based on 390 benthic invertebrate samples from near-natural streams in Germany we defined eight stream type groups by Non-metric multidimensional scaling (NMS). The taxa lists were restricted to Mollusca, Ephemeroptera, Odonata, Plecoptera, Coleoptera and Trichoptera species and evaluated on presence/absence level. At genus level, streams located in the lowlands differ from streams in lower mountainous areas and the Alps, while the two latter groups were undistinguishable. At species level, a clear separation of different stream size classes is visible in the lowlands; a second gradient is related to the bottom substrate. Streams in the Alps can be distinguished from streams in lower mountainous areas at species level. Within the lower mountainous regions a size gradient is detectable, a less obvious gradient indicates catchment geology. The resulting “bottom-up” stream typology is compared to other stream typological systems in Germany.     

Stream typology and lake outlets — a perspective towards validation and assessment from northern Germany (Schleswig-Holstein)

The objective of this paper is twofold: 1) to validate the German stream typology for Schleswig-Holstein, and 2) to develop an assessment system for lake outlets. The German stream typology, based on a top-down analysis of geomorphological variables, was validated using biotic data of streams in Schleswig-Holstein, northern Germany. A null model analysis was conducted to test for differences between seven stream types (sand streams and rivers, gravel streams and rivers, partly-mineralic streams, limnic marsh streams, and lake outlets). The dataset compiled for the statistical analysis comprised 28 streams, 65 different sampling sites, 428 samples, and 296 taxa. The analysis confirmed all stream type except partly-mineralic streams, which showed faunal overlap with all types except gravel streams. Gravel streams were the most distinctive stream type. Lake outlets were shown to be a unique type, having a distinct macroinvertebrate fauna. Furthermore it was shown, that the species composition differed between lentic and lotic outlets. Canonical correspondence analysis of 19 investigated lake outlets revealed that characteristics of the lakes had only a minor effect on macroinvertebrate community structure.

The developed assessment system of lake outlets was based on the habitat association of 132 macroinvertebrate taxa. Taxa were allotted to five categories of lake outlet preferences depending on the results from ordinations, frequency tables and abundance distributions. A qualitative and a quantitative lake outlet index (LTI) were tested with independent data sets. The quantitative LTI_quan proved to be more robust and only slightly affected by seasonal changes in the macroinvertebrate community composition. Assessments of lake outlets based on macroinvertebrates should be conducted in spring and autumn to reduce the risk of misclassifications, in particular, for boundary cases rated between good and moderate quality classes.     

Macrophytes and phytobenthos as indicators of ecological status in German lakes — a contribution to the implementation of the water framework directive

A new assessment system for macrophytes and phytobenthos in German lakes according to the Water Framework Directive of the European Community is described. Based on biological, chemical and hydromorphological data from about 100 lake sites covering the main ecoregions, hydromorphological lake types and degradation forms, biocoenotic types could be defined. For developing a classification system the quality element macrophytes and phytobenthos was divided into two components: macrophytes and benthic diatoms. For macrophytes 4 and for benthic diatoms 4 lake types were identified. The benthic vegetation at reference conditions is described and degradation is characterised as deviation in benthic vegetation species composition and abundance from the reference biocoenosis. For classification in five ecological status classes, several metrics were developed and used in combination with existing indices. For a few of the described lake types further investigations are necessary before a classification can be developed.     

Short-term effects of instream habitat restoration on macroinvertebrates and a comparison of sampling approaches

Many streams and rivers worldwide are restored with the intention to mitigate degradation caused by human activities, but these rehabilitation projects often involve physical instream work with diggers or other heavy machinery. The short-term effects of such restoration works on stream ecosystems are rarely investigated. The primary aim of our study was to assess the short-term effects of physical instream restoration works (which likely increased instream fine sediment load temporarily) on the benthic macroinvertebrate community in a lowland soft-bottomed stream, and our second aim was to compare the results of semi-quantitative kick-net and quantitative Surber sampling in this assessment. Invertebrates were collected using these two methods from three Control and three Impact sites, before and two days after recontouring the stream banks and installing instream woody cover features. Three of seven macroinvertebrate community-level indexes suggested positive short-term effects of the restoration works, whereas none indicated negative effects. By contrast, seven of the 14 most common taxa were negatively affected by the restoration works, possibly due to increased fine sediment levels reducing habitat quality for these taxa. These differences imply that taxon-specific invertebrate responses may be more suitable for detecting short-term impacts of instream restoration works than community-level metrics. Community indexes and common taxa were also likely affected by a drought in the spring and summer before restoration, which may have obscured some effects of the restoration works. Finally, kick-net and Surber sampling methods yielded similar findings for the community-level metrics but differed more for the common taxa, probably because the two methods sampled different microhabitats within the stream. Consequently, we recommend that for routine monitoring of macroinvertebrate communities in lowland soft-bottomed streams, the semi-quantitative kick-net sampling method should be used.     

The indication of morphological degradation of streams and rivers using Simuliidae

Blackfly communities from five German stream types out of two ecoregions (small and mid-sized siliceous gravel-bed mountain streams of the Central mountains, ecoregion 9, and organic type brooks, small and mid-sized sand-bottomed Central lowland streams of ecoregion 14) are compared. Ecoregional, as well as stream type-specific biocoenotic differences are discussed. The presence of Prosimulium sp. was restricted to mountain streams, whereas Simulium lineatum seemed to prefer mid-sized sand-bottomed Central lowland streams, and S. vernum showed a clear preference for Central lowland streams. An Index of Morphological Stress (IMS), derived from 22 geo-hydromorphological parameters recorded during sampling in the field, is presented. According to the IMS values, sites are divided into morphologically ‘unstressed’ sites (high or good morphological quality) and ‘stressed’ sites (moderate, poor or bad morphological quality), and biocoenotic differences of the two categories are discussed. Two stream types and the entire data set showed significantly higher numbers of taxa at ‘unstressed’ sites. Linear Multiple Regression (LMR) was used to identify geo-hydromorphological parameters that significantly explain the variance of the three most constant taxa, Prosimulium sp., P. hirtipes and Simulium sp. in the LMR model.     

Ökologische Bewertung von Tieflandbächen des Ladberger Mühlenbach-Systems im Norddeutschen Tiefland, basierend auf der Standorttypie der Trichopterenbiozönosen

In the last few years ecological evaluation of lowland freshwaters was controversely discussed. Due to the fact that most basic information of assessment systems derived from upland streams, the results could not be applied to the lowland situations. Additionally, it is not sufficient for an integral freshwater evaluation only to focus on the stream to show degradation in the tight coupling of running waters and their adjacent landscape. In this study we critically tested a new method, the Standorttypie-Index (STI), to assess lowland streams using caddis-fly communities.

During 1994 and 1996 we investigated the caddisfly community at 15 sampling sites of a river system in the “Westfälische Tieflandbucht” (Northrhine-Westphalia, Germany). As a result we found 72 species belonging to 16 families of the order Trichoptera. The calculation of the “Standorttypie-Index” is based on four defined ecological categories. Although the definitions were inaccurate, each species was classified into one category. In view of stream regulation and streamwidth, we calculated for all study sites the STI of the immature stages, the adults and a combined total STI.

Although there is a correlation between the “Standorttypie-Index” and the state of degradation of the study sites, the separate analysis of larval and adult communities showed that the results easily lead to misinterpretation. The STI of adults devalues the combined total STI of regulated as well as natural study sites. As a consequence, until now it is not possible to evaluate the state of degradation in the coupling of the stream and the adjacent landscape using the STI of the caddis-fly community.     

Application of the new multimetric MMI_PL index for biological water quality assessment in reference and human-impacted streams (Poland,the Slovak Republic)

A new multimetric MMI_PL index, which is based on the macroinvertebrate composition and combines six single key metrics, has already been implemented in Poland according to the requirements of the EU Water Framework Directive. The objectives of our survey were to assess the biological water quality using the new multimetric MMI_PL index in both reference and human-impacted streams, to analyze whether the values of the new multimetric index properly reflect the ecological status of the water in upland and mountain streams as well as to determine which environmental factors influence the distribution of benthic macroinvertebrates and the values of the metrics. The study was carried out from 2007 to 2010 in three Ecoregions that were established by the EU WFD. A total of 60 sampling sites: 36 reference sites that were situated in the headwaters of mountain streams at mid- and high-altitudes and 24, human-impacted sampling sites were selected. The benthic macroinvertebrate surveys were supported by both a hydromorphological and macrophyte assessment according to the River Habitat Survey (RHS) and to the Macrophyte Methods for Rivers. Canonical correspondence analysis (CCA) showed that the values of the Habitat Quality Assessment (HQA) index, conductivity, pH and altitude were the parameters most associated (statistically significant) with the distribution of benthic macroinvertebrate taxa and the values of the metrics in both the reference and human-impacted (impaired) sections of the streams in Ecoregions 9, 10 and 14. The new MMI_PL index was useful for biological water quality assessment and was also important for separating both the reference and impaired sections of streams. The MMI_PL index and some key metrics performed contrary to what was expected in relation to the reference high-altitude siliceous streams (the High Tatra Mts., Ecoregion 10). Low values of multimetric index and key metrics did not properly reflect their high ecological status and pristine character as reflected by the hydromorphological (RHS) and macrophyte surveys or the physical and chemical parameters of the water.     

A new fish-based multi-metric assessment index for cyprinid streams in the Iranian Caspian Sea Basin

A major issue for water resource management is the assessment of environmental degradation of lotic ecosystems. The overall aim of this study is to develop a multi-metric fish index for the cyprinid streams of the Caspian Sea Basin (MMICS) in Iran. As species diversity and composition as well as population structure in the studied streams are different to other regions, there is a substantial need to develop a new fish index. We sampled fish and environmental data of 102 sites in medium sized streams. We analysed human pressures at different spatial scales and determined applicable fish metrics showing a response to human pressures. In total, five structural and functional types of metrics (i.e. biodiversity, habitat, reproduction, trophic level and water quality sensitivity) were considered. In addition, we used 29 criteria describing major anthropogenic human pressures at sampling sites and generated a regional pressure index (RPI) that accounted for potential effects of multiple human pressures.For the MMICS development, we first defined reference sites (least disturbed) and secondly quantified differences of fish metrics between reference and impaired sites. We used a Generalised Linear Model (GLM) to describe metric responses to natural environmental differences in least disturbed conditions. By including impaired sites, the residual distributions of these models described the response range of each metric to human pressures, independently of natural environmental influence.Finally, seven fish metrics showed the best ability to discriminate between impaired and reference sites. The multi-metric fish index performed well in discriminating human pressure classes, giving a significant negative linear response to a gradient of the RPI. These methods can be used for further development of a standardised monitoring tool to assess the ecological status and trends in biological condition for streams of the whole country, considering its complex and diverse geology and climate.     

Effects of watershed land use on sources and nutritional value of particulate organic matter in temperate headwater streams

Suspended particulate organic matter (POM) in headwater streams is an important source of food and energy to stream food webs. In order to determine the effects of watershed land use on the sources and characteristics of POM, we compared the lipid composition of POM (fatty acid, aliphatic alcohol and sterol) from streams influenced by different types of watershed land use. Eight first-order streams discharging to the York River Estuary (Virginia, USA) were sampled during baseflow conditions bi-monthly from February to November 2009, including streams draining forest-dominated, pasture-dominated, cropland-dominated, and urban land-dominated watersheds. Allochthonous vs. autochthonous lipids showed that POM in most of these streams was dominated by allochthonous sources (59.5 ± 14.2 vs. 39.6 ± 14.5 % for aliphatic alcohols and 52.9 ± 11.5 vs. 34.1 ± 10.3 % for sterols). The relative abundance of allochthonous vs. autochthonous lipid inputs to POM varied as a function of land use type. POM in streams draining forest-dominated watersheds contained a higher proportion of allochthonous lipids and a lower proportion of autochthonous lipids than the streams influenced by human land use. The contribution of bacterial fatty acids differed significantly among sampling times (P = 0.003), but not among land use types (P = 0.547). Stepwise linear regression model selected nitrate and temperature as the best predictors of variation in bacterial inputs to POM. Proxies used to assess the nutritional value of POM potentially available to stream consumers included C:N ratios, and the concentrations of total long-chain polyunsaturated fatty acids, eicosapentaenoic acid, arachidonic acid, and cholesterol. None of these nutritional proxies differed among sampling months (P ≥ 0.171), but the proxies showed that the nutritional value of POM in forest streams was lower than in urban streams. Collectively, these findings suggest that human land use in upstream watersheds alters the source composition and nutritional value of stream POM, which not only impacts food quality for stream biota, but also potentially changes the characteristics of OM reaching downstream ecosystems.     

Defining a disturbance gradient in a Middle-Eastern River Basin

A physical, chemical and biological characterization of river systems is needed to evaluate their ecological quality and support restoration programs. Herein, we describe an approach using water chemistry, physical structure and land use for identification of a disturbance gradient existing in the Karun River Basin. For this purpose, at each site, physical structure and physico-chemical data were collected once in each season for a total of 4 samples during the period (October 2018 - September 2019). Principal components analysis (PCA) of 17 variables identified five variables that were influential across all seasons: conductivity, total habitat score, stream morphology, clay & silt, and sand. Of the 54 sites, 14, 26 and 14 sites were classified as least, moderate and most disturbed sites, respectively. The metric Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa was used for validation of the classification. Results in different seasons showed that all the least disturbed sites (n = 14) were significantly different from moderate and most disturbed sites (p < 0.01). In this study the validation process presented good confirmation of a priori reference sites selection, showing that the proposed criteria could be considered as appropriate tools for characterization of the existent disturbance gradient in the Karun River Basin.     

Active reintroduction of benthic invertebrates to increase stream biodiversity

A large number of restoration projects aims to improve the ecological quality of streams and rivers by focusing on the stream structure. However, improved habitat heterogeneity often does not lead to natural recolonization by sensitive freshwater macroinvertebrate communities, particularly when the recolonization potential is low and source populations are absent. In preliminary studies we tested whether natural substrate exposures could be used to sample and transport benthic macroinvertebrates. In this pilot study we used these previously tested natural substrate exposures to sample freshwater invertebrates in a donor stream in order to actively (re-)colonize a recipient stream. In the course of three reintroduction campaigns, we were able to accumulate over 350,000 benthic invertebrates, including 25 indicator taxa of the orders Ephemeroptera, Plecoptera and Trichoptera and 30 taxa scoring positive in the German Fauna Index. In total, 45 taxa, which did not occur in the recipient stream before, were reintroduced. They were transported gently within natural substrate exposures and released on a stream bottom area of 500 m² in the recipient stream. We intended to study if an increase of benthos fauna in a recipient stream is possible, and if this increase will eventually improve the ecological status. So far, the natural substrate exposure-method demonstrated to be an adequate tool to accumulate and transport benthic macroinvertebrates and, in general, has the potential to increase the biodiversity of streams when used as assisted migration measure.