Assessing streams in Germany with benthic invertebrates: selection of candidate metrics

The process of selecting invertebrate-based candidate metrics for the German stream assessment system is described. The aim was to identify metrics indicating degradation types other than organic pollution and acidification (“general degradation”). For 18 out of 24 German stream types a data base of roughly 2,000 benthic invertebrate samples was generated; for each sample 79 metrics were calculated. Data on land use in the catchment were compiled for all sampling sites, together with data on hydromorphology for many sampling sites. Hydromorphological and land use parameters, which describe a clear gradient in the data sets were identified by Non-metric Multidimensional Scaling (NMS). Correlation analyses between land use/hydromorphological parameters and metric results were calculated separately for the individual stream types. Among those metrics best indicating catchment- and hydromorphological degradation in the majority of stream types are: proportion of Ephemeroptera, Plecoptera and Trichoptera; proportion of Plecoptera (mainly suited for mountain streams); number of Plecoptera taxa; proportion of xenosaprobic taxa; proportion of epirhithral preferring taxa. Differences of metric correlations between stream types and between degradation types are discussed, leading to a list of candidate metrics for assessing German streams.     

Response of macroinvertebrate communities to thermal regime in small Mediterranean streams (southern South America): Implications of global warming

The seasonal nature of the stream thermal regime has been recognized as an important factor for the structure of benthic macroinvertebrate communities. In this study, we show the importance of temperature and the potential implications of global warming on the composition of benthic macroinvertebrate communities in Andean watersheds. Here we show that thermal factors (mean temperature and monthly range) partially explain the seasonal variability of macroinvertebrates in Andean streams. Different thermal requirements were observed for macroinvertebrate families. Optimal monthly mean temperatures estimated for Gripopterygidae (Plecoptera), Hydrobiidae (Gastropoda) and Helicophidae (Trichoptera) were lower than 7 °C, while temperatures for Ameletopsidae, Baetidae (Ephemeroptera), Ecnomidae, Limnephilidae, Hydropsychidae, Leptoceridae (Trichoptera), Elmidae (Coleoptera) and Notonemouridae (Plecoptera) were close to 9.5 °C.According to our estimations, future global warming could cause important changes in the macroinvertebrate composition of Andean watersheds. Gripopterygidae, Austroperlidae, Diamphipnoidae (Plecoptera), Hydrobiidae and Helicophidae (Trichoptera) would be the most vulnerable families under the 2090 temperature predictions due to their preference for low temperature.     

Do installed stream logjams change benthic community structure?

Installed logjams constructed of wood are commonly used in stream restoration projects to provide habitat for lotic organisms. Macroinvertebrate densities are known to increase on logjam surfaces; however, less is known about the influence logjams have on benthic organisms inhabiting the surrounding streambed. To examine this, we conducted a before-after-control-impact (BACI) study in a stream in northern Minnesota, USA, to determine how an installed logjam affected the richness and abundance of three insect orders commonly used in biotic indices, the Ephemeroptera, Plecoptera, and Trichoptera (i.e., EPT taxa). A spanning logjam composed of three logs bound together was installed perpendicular to stream flow at the impact site. Initial sampling of the impact site and an upstream control found no differences among the ETP taxa. A year after installation, the logjam accumulated woody debris and altered flow so that near-bed current at the impact site was faster and more heterogeneous than at the control site. Although the richness and abundance of the macroinvertebrate community as a whole did not differ between sites after one year, it did for the Ephemeroptera and Plecoptera at the impact site. By contrast, Trichoptera richness and abundance did not change. Our results lend support to the hypothesis that installed logjams may enhance stream habitat not only by providing colonization surfaces for macroinverbrates, but also by altering the benthic environment of the surrounding habitat.     

Trophic guilds of EPT (Ephemeroptera,Plecoptera, and Trichoptera) in three basins of the Brazilian Savanna

Insects of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) are prominent among stream biota and are associated with many ecological processes in these environments, meaning that a proper definition of their habits is essential. We studied EPT from three watersheds in Brazil (Paraguai, Paraná, and São Francisco) in order to (i) determine the trophic guilds of EPT genera sampled; (ii) determine whether trophic guilds reflect EPT phylogenetic component (taxonomic distance); (iii) compare trophic guild composition among watersheds; and (iv) verify the effect of environmental components in trophic guild composition. Eight trophic guilds were determined based on gut content analysis: detritivores, fine-detritivores, fine-detritivores/algivores, coarse-detritivores, coarse-detritivore/algivores, periphytivores, carnivores, and omnivores. Caddisflies presented the most variable diet and many genera belonged to different trophic guilds in different basins. Overall trophic guild composition did not reflect the taxonomic distance among taxa and it did not differ among the three basins. Instead, EPT guilds were related to local environmental variables, evidencing that their diet probably varies according to local resource availability, highlighting the importance of empirical assessments of diet for ecological studies.     

The taxonomical and functional diversity of three groups of aquatic insects in rheocrene karst springs are affected by different environmental factors

Karst springs represent valuable and often the most threatened habitats in the riverine landscape. Unlike other stream habitats, they have several specifics that determine their insularity in the river continuum, e.g., high seasonal thermal and chemical stability. The presented study aimed to find out the taxonomical and functional richness of three groups of aquatic insects (Ephemeroptera, Plecoptera and Trichoptera) in the Western Carpathians karst springs, as well as uncover the mechanism of the EPT community assembly. Low within-site species richness was generally found, however, there was high between-site diversity and thus high total diversity of the studied groups of benthic invertebrates as well. Species richness of the EPT community was higher in larger and colder springs: those with lower concentrations of CO₂ and Fe, as well as higher concentrations of SO₄²⁻. Analysis of functional richness, as well as functional dispersion, did not reveal any clear assembly mechanism in the spring EPT community; however, both analyses indicated a higher proportion of environmental filtering there. Unlike the taxonomic richness, the functional richness of the EPT community was significantly higher in small and medium springs with higher water temperatures, as well as in springs with the presence of deadwood. Between-site dissimilarities in the functional composition of EPT were significantly correlated with environmental differences of springs, which determined variables such as spring size and temperature, as well as the concentration of CO₂ and SiO₂.     

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.     

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.     

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.     

Spatial differences in denitrification and bacterial community structure of streams: relationships with environmental conditions

In streams, benthic bacterial communities are integral to multiple aspects of ecosystem function, including carbon and nitrogen cycles. Variation both in terms of bacterial community structure (based on taxonomic and/or functional genes) and function can reveal potential drivers of spatiotemporal patterns in stream processes. In this study, the abundance and diversity of 16S rRNA genes and abundance of nosZ genes, encoding for nitrous oxide reductase, were related to denitrification and environmental conditions. Denitrification rates varied among the three streams examined, and within a given stream there were significant longitudinal differences. Likewise, bacterial community structure based on analysis of the 16S rRNA gene also differed significantly among streams. However, variation in denitrification rate was not well correlated with environmental or biological variables measured. In addition, relatively large numbers of denitrifiers occurred when denitrification rates were low. In conclusion, although the streams differed in environmental conditions as well as bacterial community structure, these differences did not explain much of the spatial variation in denitrification rates.     

An improved index of environmental quality for Swiss rivers based on benthic invertebrates

A total of 1424 samples of benthic invertebrates, collected in 56 rivers of western Switzerland (canton of Vaud), was used to improve the RIVAUD (Rivers of Vaud) index of environmental quality. This index, described for the first time in 1989, was based on total number of taxa and on number of taxa intolerant of pollution (Plecoptera, Heptageniidae, and Trichoptera with a case). The 1995 version of RIVAUD, called RIVAUD 95, presented a larger range of values (0–20) than the previous one (0–10), to describe more precisely the variations of environmental quality. According to RIVAUD 95, the environmental quality of Swiss rivers increased with the altitude of sampling sites because anthropogenic impacts decreased along the same gradient. This altitudinal pattern was used to define classes of environmental quality which can be adapted to the rivers of other regions.     

Assessment of a Mediterranean shallow lentic ecosystem (Lake Pamvotis, Greece) using benthic community diversity: Response to environmental parameters

Macroinvertebrates play a key role in freshwater lentic and lotic ecosystems. The macroinvertebrate benthic community of a shallow Mediterranean lake (Lake Pamvotis, NW Greece) was studied. The benthic assemblage was sampled monthly at five sites during a period of 1 year (Apr. 1998–Mar. 1999). In addition hypolimnetic water quality variables were monitored over the same period at each site.

The aim of the study was (a) to describe the intra-annual and spatial variability in benthic communities, (b) to relate possible community changes to environmental conditions and (c) to evaluate the responses of the lake's ecological status on community indices.

The benthic fauna of Lake Pamvotis was found to be very limited with a total of 10 species belonging to five taxonomic groups. The oligochaete community comprised 80% of the total benthic fauna with Potamothrix bavaricus as a new record for the Lake Pamvotis and Potamothrix hammoniensis, being the dominant benthic species represented more than 61% of the total benthic fauna. Chironomus plumosus was the most abundant chironomid species contributing with about 6% of the total benthic fauna, and Chaoborus flavicans with 19% was the important dipteran. Almost all benthic species showed the same intra-annual seasonal pattern, with peak population densities during spring and early summer except P. hammoniensis which predominated during the whole sampling period. Dissolved oxygen and temperature seemed to be the main environmental factors affecting community indices.

Benthic communities are affected by human disturbances in Lake Pamvotis shifting their composition to more tolerant taxa, reflecting also the eutrophic to hypertophic character of the lake.     

Evaluating water quality for Amazonian streams along the interoceanic highway in Peru using macroinvertebrates collected by hand and with leaf packs

We assessed water quality using physical, chemical, and biological characteristics in 37 streams between Puerto Maldonado and Cusco in Peru. Study sites ranged from ∼200 to 4000 m in elevation, with streams selected as pairs (control/natural vs. human impacted) along this gradient. In general, temperature decreased (R² = 0.82) and other parameters increased [dissolved oxygen (R² = 0.19), conductivity (R² = 0.17), pH (R² = 0.37)] with elevation. Macroinvertebrates were hand collected by professional entomologists and using leaf packs implemented by conservation workers. The professionals identified 213 unique taxa from the hand collections, with 80 species collected only one time. Data from control streams showed that as elevation increased, total richness (p = 0.008) and EPT richness (p = 0.050) decreased whereas Diptera richness increased (p = 0.002). NMS ordination indicated significant differences in macroinvertebrate assemblages when control streams from low and high elevations were contrasted. Hand collections also revealed significant differences between control and impact streams for total richness, EPT richness and % Diptera, but not for % EPT, % EPT richness, or % Diptera richness. The majority of the deployed leaf packs were successfully retrieved and contained many macroinvertebrates (Avg. = 141 individuals per pack). There were 98 unique taxa (family level or higher) identified from the leaf packs by the trained conservation workers. Fourteen of 15 macroinvertebrate community metrics (at the family level) were able to detect significant differences between control and impact sites. All of the family level metrics responded similarly across the elevation gradient except total richness, EPT richness, EPT count, and % Hydropsychids. Both the Costa Rica and the Virginia Save Our Stream Indexes were able to differentiate control from impacted streams using leaf pack data. Although the diversity of macroinvertebrates was higher for hand collections relative to leaf packs (due to greater habitats sampled and higher taxonomic resolution), leaf pack samples were better able to distinguish control from impacted streams. Specifically, leaf packs were able to discern impacts in streams at low elevation better than those at high elevation. Generally, macroinvertebrates indicated impact from urbanization to be worse than impacts from other human activities (i.e., gold mining and agriculture). Overall, hand collections will serve as an important reference of species diversity going forward while leaf packs processed by trained conservation workers are a viable method to monitor stream water quality in Peru and perhaps elsewhere.     

Streams in the Harz National Parks (Germany) — a hydrochemical and hydrobiological evaluation

Between 1995 and 2001, 16 measuring points at small and medium sized brooks in the Harz National Parks were sampled. The samples have been evaluated by means of hydrochemistry and macroinvertebrate biology. Although nearly all streams are largely uncontaminated by oxygen-consuming substances, they are settled only by a small number of macroinvertebrate species. There is a clear correlation between this number and pH. The reduction in species number with decrease of pH is mainly caused by the absence of most Ephemeroptera, some Coleoptera and Trichoptera. Comparing biological evaluation of acidity with physico-chemical measurements, a unacceptable underestimation was found. The reason could be that different sensitivities to acidification between regional populations seem to exist.

Despite of the low species number, there is a very specific macroinvertebrate fauna that emphasizes the conservation value of the Harz National Parks.     

Taxonomic composition and seasonality of diatoms in three Dinaric karstic lakes in Croatia

The composition and temporal distribution of planktonic diatoms were studied in three small shallow karstic lakes – Modro Oko, Desne, and Kuti – throughout the seasons in 1994, 1995, 1997, and 1998. Physico-chemical parameters did not differ among the three lakes, except for NO₃ concentrations. Altogether, 137 diatom taxa within 41 genera were found in all three lakes combined. The highest number of taxa belonged to the genera Surirella (13), Navicula (12), andCymbella (9). Most taxa were tychoplanktonic, with true panktonic taxa contributing only 14% of the total. Despite their physical-chemical similarity, the lakes showed differences in the structure and dynamics of their diatom communities. Blooms occurred at different times in each of the lakes, and community similarity (Jaccard index) among all three was low (17.6–29.1%). The highest mean values of surface diatom abundance in Modro Oko (2199 cells L⁻¹), Desne (7900 cells L⁻¹), and Kuti (20690 cells L⁻¹) were not significantly different. Margalef's species richness index did not differ either among the lakes or seasonally. Only five diatom taxa in quantitative samples, and 22 taxa in net-samples, were common to all lakes. The most frequent diatoms were Cyclotella striata (56–93%), Fragilaria ulna (50–67%), and Asterionella formosa (27–83%). The most abundant taxa in Modro Oko, Desne, and Kuti were, respectively, Cymbella sp. 1 (402 cells L⁻¹), Cyclotella striata (3000 cells L⁻¹) and Asterionella formosa (20690 cells L⁻¹). Eighteen taxa were recorded for the first time in Croatia: Amphora commutata, Caloneis amphisbaena var. subsalina, C. silicula var. peisonis, Campylodiscus echeneis, Coscinodiscus lacustris, Denticula elegans, Gyrosigma acuminatum var. lacustre, G. distortum var. parkeri, G. fasciola, Navicula menisculus var. menisculus, N. pusilla, N. helensis, Stauroneis parvula var. prominula, Staurosira construens f. subsalina, Stephanodiscus sp. 1, Surirella gracilis, S. ovalis, and S. striatula. The genus Stephanodiscus was recorded for the first time in Croatia.     

Benthic macroinvertebrates as indicators of the water quality in Bulgaria: A case-study in the Iskar river basin

Macroinvertebrates were sampled at 15 locations in the Iskar river basin in Bulgaria for the purpose of water quality assessment. Based on the chemical as well as the biological parameters, it was concluded that the water quality was still good upstream of Sofia, however, despite a huge waste water treatment plant, a strong decrease was observed when the river passed Sofia. Due to self-purification and dilution, a gradual amelioration of the water quality was observed 40 and 80 km downstream of Sofia, however, water quality was still insufficient. The Irish Biotic Index (IBI), which is currently used in Bulgaria for the national monitoring of macroinvertebrates for water quality assessment, does not fulfil the requirements of the European Union Water Framework Directive (WFD). The Multimetric Macroinvertebrate Index Flanders (MMIF), on the contrary, is a WFD compliant method developed for the northern part of Belgium, which is based on (1) the total number of taxa, (2) the number of Ephemeroptera, Plecoptera and Trichoptera taxa, (3) the number of other sensitive taxa, (4) the Shannon–Wiener index and (5) the mean tolerance score. The outcome of this MMIF was strongly correlated with the outcome of the Irish Biotic Index. Therefore, it should be possible to develop a similar multimetric index for macroinvertebrates to evaluate the biological water quality in Bulgaria without much effort.     

Comparing modified biological monitoring working party score system and several biological indices based on macroinvertebrates for water-quality assessment

Macroinvertebrate communities from the lower Nysa Kłodzka River catchment, southern Poland, were analyzed seasonally, in order to assess changes in their composition and structure, in relation to water quality. Two major groups of sites, differing in both morphological structure and taxonomical composition by cluster analysis, were identified within the catchment area. Wider and deeper sites, located along the Nysa Kłodzka River, were associated with the dominance of Chironomidae. Sites assigned along tributaries were characterized by a diversified structure of dominant taxa, including Oligochaeta, Hirudinea, Crustacea, Trichoptera, Ephemeroptera and Diptera. The performance of the modified procedure, named BMWP(PL) index, in accurately classifying 26 sites has been assessed through comparison with saprobic, diversity and biotic indices as well as chemical data. Due to diversified taxa richness and the presence or absence of specific indicator groups, values of the BMWP(PL) index varied from 27 to 93, and were correlated with the other biological indices and chemical variables. It has been stated that there is strong potential for application of the BMWP(PL) system in Poland, although some further testing is recommended.     

Multimetric Macroinvertebrate Index Flanders (MMIF) for biological assessment of rivers and lakes in Flanders (Belgium)

The European Water Framework Directive requires that member states assess all their surface waters based on a number of biological elements, including macroinvertebrates. Since 1989, the Flemish Environment Agency has been using the Belgian Biotic Index for assessing river water quality based on macroinvertebrates. Throughout the years, the Belgian Biotic Index has proven to be a reliable and robust method providing a good indication of general degradation of river water and habitat quality. Since the Belgian Biotic Index does not meet all the requirements of the Water Framework Directive, a new index, the Multimetric Macroinvertebrate Index Flanders (MMIF) for evaluating rivers and lakes was developed and tested. This index was developed in order to provide a general assessment of ecological deterioration caused by any kind of stressor, such as water pollution and habitat quality degradation. The MMIF is based on macroinvertebrate samples that are taken using the same sampling and identification procedure as the Belgian Biotic Index. The index calculation is a type-specific multimetric system based on five equally weighted metrics, which are taxa richness, number of Ephemeroptera, Plecoptera and Trichoptera taxa, number of other sensitive taxa, the Shannon-Wiener diversity index and the mean tolerance score. The final index value is expressed as an Ecological Quality Ratio ranging from zero for very bad ecological quality to one for very good ecological quality. The MMIF correlates positively with dissolved oxygen and negatively with Kjeldahl nitrogen, total nitrogen, ammonium, nitrite, total phosphorous, orthophosphate and biochemical and chemical oxygen demand. This new index is now being used by the Flemish Environment Agency as a standard method to report about the status of macroinvertebrates in rivers and lakes in Flanders within the context of the European Water Framework Directive.     

Influence of bed heterogeneity and habitat type on macroinvertebrate uptake in peri-urban streams

The role of geomorphic structure, referred to as physical heterogeneity, and its influence upon the colonization of habitat by macroinvertebrates was analysed in the peri-urban, Twin Streams Catchment, in West Auckland, New Zealand. Using a cross-scalar approach, 4 riffle-run assemblages were analysed in each of 2 River Styles (a confined, low sinuosity, gravel bed river and a partly confined, low sinuosity, bedrock, cobble, and gravel bed river). Each of these 8 locations comprised 2 distinct sampling areas; the upstream zone had a more heterogeneous river bed with a high diversity of physical features and flow, whilst the downstream area had a more homogeneous structure. Microhabitat features sampled at each site included streambed material, bank margins, fine grained organic debris, wood, and boulders. Habitat mosaics and their associated macroinvertebrate relationships followed a semi-predictable but interrupted pattern, supporting the view that river systems are a patchy discontinuum. Homogeneous zones were more frequently characterised by higher proportions of Trichoptera than heterogeneous zones, whilst heterogeneous zones were frequently characterised by Plecoptera and Ephemeroptera. Diversity was maximised when the species pools from heterogeneous and homogeneous sites were combined for any given site. Functional habitats influenced macroinvertebrate assemblages in non-linear and complex ways. Wood and organic debris habitats were associated with high diversity, abundance, and sensitive species whereas streambed habitat was usually associated with low diversity. A diverse range of physical zones that approximates the 'natural range of behaviour' for the given type of stream was considered to provide a more effective platform for rehabilitation planning than emphasising heterogeneity of physical structure in its own right.     

Environmental determinants of species turnover of aquatic Heteroptera in freshwater ecosystems of the Western Ghats,India

Partitioning beta diversity into its two components of spatial turnover and nestedness is a more robust method for checking spatial variability in biological communities than calculating the total beta diversity alone. The relative contribution of spatial turnover and nestedness has been used to test the effects of climatic, environmental, spatial and temporal variables on community composition. In this study, we tested the effects of environmental factors and microhabitat features on total beta diversity and its spatial turnover and nestedness components using a comprehensive dataset of aquatic Heteroptera collected from four types of permanent freshwater habitats (i.e. streams, ponds, rock tanks and reservoirs) in the Western Ghats of India. We observed that communities in all four types of habitats were predominantly shaped by dissimilarity caused due to spatial turnover (>85 %). Each type of habitat showed the presence of one or more species uniquely associated with it, which might contribute to the turnover between communities. The abiotic environment (climatic factors, topological factors, soil characteristics and microhabitat features) as well as assemblage structure differed significantly between habitat types. Communities in each type of habitat were affected by different environmental factors, such as precipitation and temperature patterns for streams, altitude and rocky substrate for rock tanks, and soil characteristics and the presence of aquatic macrophytes for ponds and reservoirs. Assemblages observed in the four types of permanent habitats are thus compositionally distinct due to species replacements between local communities, which in turn are strongly influenced by environmental variables. Similar to previous studies, our results show that spatial turnover largely measures the same phenomenon as total beta diversity on a regional scale.