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The aim of our study was to compare the richness and composition of macroinvertebrate assemblages in natural reed and artificial rip-rap habitats in a shallow lake 50+ years after shoreline modifications. Lake Balaton (Hungary) provided a unique study system as approximately half of its shoreline (c.105 km) has been modified. Littoral macroinvertebrates were collected in two habitat types (artificial rip-rap and natural reed) around the shoreline over two seasons. We found that native taxon richness of rip-rap habitat was only one-twentieth of the natural reed habitat. Rip-rap habitat harboured significantly more alien species. We found that the proportion of alien taxa was higher in rip-rap habitat (89.2%) than in reed habitat (16.7%). The composition of macroinvertebrate assemblages in the two habitats was also significantly different with limited to moderate overlap. Furthermore, all 8 indicator taxa of rip-rap habitat were alien, whilst all 28 indicator taxa were native in reed habitat. These results suggest that artificial engineering structure creates a novel ecosystem dominated by alien species.

In 2018 and 2019, quantitative aquatic macroinvertebrate samplings were carried out in the river network of the Bükkösdi-víz (Mecsek Mountain). The identification of 325,865 macroinvertebrate specimens originated from 40 sampling sites resulted in the occurrences of 125 different species belonging to 12 higher taxa (Gastropoda – 9, Bivalvia – 1, Hirudinea – 4, Malacostraca – 6, Ephemeroptera – 16, Odonata – 12, Plecoptera – 3, Heteroptera – 19, Coleoptera – 23, Megaloptera – 3, Neuroptera – 1, Trichoptera – 28), including 8 protected (Bivalvia: Unio crassus, Odonata: Calopteryx virgo, Coenagrion ornatum, Gomphus vulgatissimus, Onychogomphus forcipatus, Orthetrum brunneum, Heteroptera: Aquarius najas, Neuroptera: Osmylus fulvicephalus) and 1 strictly protected species (Odonata: Cordulegaster heros).

We present the results of the first-ever DNA barcoding study of odonates from the Maltese Islands. In total, 10 morphologically identified species were collected during a two-week long expedition in 2018. Eighty cytochrome c oxidase subunit I (COI) barcodes were obtained from the collected specimens. Intra- and interspecific distances ranged from 0.00% to 2.24% and 0.48% to 17.62%, respectively. Successful species identification based on ascribing a single morphological species to a single Barcode Index Number (BIN) was achieved for eight species (80%). In the case of two species, Ischnura genei and Anax parthenope, BINs were shared with other closely related species. The taxonomic status of I. genei is questionable and the phylogenetic relationship between A. imperator/parthenope is not clear. Further studies involving a series of adult specimens collected in a wide spatial range and nuclear markers are necessary to resolve these cases. Therefore, this dataset serves as an initial DNA barcode reference library for Maltese odonates, within a larger project: Aquatic Macroinvertebrates DNA Barcode Library of Malta.

The Asian clam (Corbicula fluminea) is one of the rapidly spreading, very successful aquatic invasive species, which has become established widely in many parts of the world. Its spread is assumed to be by both passive and active dispersal. However, the importance of active pedal movement in dispersal is hardly known. Since there was no direct evidence of this phenomenon, field observations were combined with laboratory experiments to find out if the clams move upstream actively, and how this is affected by the quality of the substrate, the density of the clams, and the water velocity. Field observations were conducted at a small watercourse with no waterborne transport. Experiments were done in an indoor artificial stream system, where the distances moved by adult clams were measured via digital image analysis. Substrate grain size, starting density of clams, and water velocity significantly affected clam movement. Fine grain sediment and slow flow velocity both facilitated spread, while there was no clear pattern of density-dependent dispersal. Also, we found no clear preference for either upstream or downstream movement. The maximum distance moved in the lab experiments predicts no more than 0.15 km/y active pedal movement in an upstream direction, while our field observations detected a much faster (0.5–11 km/y) upstream movement, which might be explained by passive dispersal, such as via human transport and ecto- or endozoochory. Overall, it seems that active movement of the species cannot read to long-distance migration.

Stream macroinvertebrates, as non-target organisms, may face with either a single or a complex stressor during a restoration treatment. We quantified the structural, phylogenetic, and functional responses to both single (water retention) and complex (water retention and grazing) stressors and analysed how the ecological quality changes, in order to reveal the potential unwanted consequences in a soda pan restoration. Species composition has been restructured and taxonomic diversity decreased significantly as a response to the complex stressor, while they did not change under the single stress. Neither the single nor the complex stressor influenced the phylogenetic diversity. Functional diversity showed mainly no or reversible changes. Changes in diversity metrics induced changes in Ecological Quality Ratios, but the ecological state decreased only under the complex stressor. Our results suggest that different facets of alpha diversity (taxonomic, functional and phylogenetic) are complementary and provide different information about community assembly against different stresses. We can support the opinion that taxon, phylogenetic and functional diversity are proper metrics in their own way to assess the impact of stress, but it is necessary to apply them together. Ecological knowledge of this paper could be considered throughout future conservation planning and enhance restoration success in aquatic environments.

Repeatability is the cornerstone of science, and it is particularly important for systematic reviews. However, little is known on how researchers’ choice of database, and search platform influence the repeatability of systematic reviews. Here, we aim to unveil how the computer environment and the location where the search was initiated from influence hit results.We present a comparative analysis of time‐synchronized searches at different institutional locations in the world and evaluate the consistency of hits obtained within each of the search terms using different search platforms.We revealed a large variation among search platforms and showed that PubMed and Scopus returned consistent results to identical search strings from different locations. Google Scholar and Web of Science's Core Collection varied substantially both in the number of returned hits and in the list of individual articles depending on the search location and computing environment. Inconsistency in Web of Science results has most likely emerged from the different licensing packages at different institutions.To maintain scientific integrity and consistency, especially in systematic reviews, action is needed from both the scientific community and scientific search platforms to increase search consistency. Researchers are encouraged to report the search location and the databases used for systematic reviews, and database providers should make search algorithms transparent and revise access rules to titles behind paywalls. Additional options for increasing the repeatability and transparency of systematic reviews are storing both search metadata and hit results in open repositories and using Application Programming Interfaces (APIs) to retrieve standardized, machine‐readable search metadata., The consistency level with which scientific search platforms return hits for the same search initiated at different locations and from different computing environments was investigated. Scopus and PubMed returned the same results regardless of the location or computing environment but Web of Science and Google Scholar varied substantially. Since this is a crucial issue for the repeatability of systematic reviews, action should be taken to improve the within‐database consistency in the returned search hits.

Repeatability is the cornerstone of science and it is particularly important for systematic reviews. However, little is known on how database and search engine choices influence replicability. Here, we present a comparative analysis of time-synchronized searches at different locations in the world, revealing a large variation among the hits obtained within each of the several search terms using different search engines. We found that PubMed and Scopus returned geographically consistent results to identical search strings, Google Scholar and Web of Science varied substantially both in the number of returned hits and in the list of individual articles depending on the search location and computing environment. To maintain scientific integrity and consistency, especially in systematic reviews, action is needed from both the scientific community and scientific search platforms to increase search consistency. Researchers are encouraged to report the search location, and database providers should make search algorithms transparent and revise access rules to titles behind paywalls.

Taxonomic and functional patterns of macroinvertebrate communities were investigated to reveal the importance of different habitat units within a marsh system in maintaining its macroinvertebrate d...

Partition of beta diversity into components is a modern method that allows inferences about the underlying processes driving metacommunities. Based on two alternative approaches, we examined the patterns of beta diversity components of chironomids in relation to environmental and spatial gradients in three contrasting freshwater ecosystems. Beta diversity and its replacement component increased from environmentally less heterogeneous lake, through more complex wetland to stream network. Constrained ordination revealed that environmental heterogeneity and spatial processes explain some variation of the patterns of pairwise beta diversity components. Both beta diversity partitioning approaches emphasised the importance of habitat structure and food resource in structuring chironomid metacommunities. However, concurrent approaches provided contrasting results regarding the relative role of underlying mechanisms related to species replacement and richness. Therefore, further research is needed to clarify which of the beta diversity partitioning approaches should be preferred more widely in ecological studies.

Considering the ongoing loss of aquatic habitats, anthropogenic ponds are gaining importance as substitute habitats. It is therefore important to assess their functioning in comparison to their natural precursors. Here we assess the biodiversity value of sodic bomb crater ponds by comparing their gamma diversity to that of natural reference habitats, astatic soda pans, and assess their importance on the landscape level by studying alpha and beta diversity. We studied aquatic organisms ranging from algae to vertebrates in a dense cluster of 54 sodic bomb crater ponds in Central Europe. Despite the overall small area of the pond cluster, gamma diversity was comparable to that found in surveys of natural habitats that encompassed much wider spatial and temporal scales. We also found a considerable number of species shared with reference habitats, indicating that these anthropogenic habitats function as important refuge sites for several species that are associated with the endangered soda pans. Moreover, we found a number of regionally or worldwide rare species. Among the components of beta diversity, species replacement dominated community assembly. Individual ponds contributed similarly to beta diversity in terms of replacement, being equally important for maintaining high gamma diversity and emphasising the role of the pond network rather than individual ponds. This pattern was seen in all studied groups. Bomb crater ponds therefore acted as important contributors to aquatic biodiversity. Considering the tremendous losses of ponds throughout Europe, anthropogenic ponds should be taken into consideration in nature conservation, especially when occurring in pond networks.

Although the influence of invasive species on the distribution of native species is well-studied, our knowledge on the processes driving the co-occurrence of native gammarid species is limited. We studied the co-occurrence of two common European gammarids, Gammarus fossarum and Gammarus roeselii, along a stream continuum in Mecsek Mountains, SW Hungary. We hypothesized that (1) the large scale distribution is influenced by microhabitat diversity; (2) the distribution of each species is equal among the available microhabitats in the absence of a competitor; (3) microhabitat preference is evident in the case of coexistence; and (4) the mesohabitat structure influences the microhabitat preference. A longitudinal gradient was observed along the stream: The dominance of G. fossarum at upstream sections continuously transitioned into the dominance of G. roeselii through an intermediate section, where both species coexisted. This distribution cannot be completely explained by the microhabitat diversity. In cases of single species occurrences, no microhabitat preference was found in G. fossarum, whereas G. roeselii preferred lithal and biotic microhabitats. The presence of a competitor significantly modified the microdistribution: G. roeselii retreated from lithal microhabitats and G. fossarum almost disappeared from gravel. Moreover, the location of microhabitats within mesohabitats significantly affected the distribution of gammarids. Both species occurred in meso- and microhabitat combination resembling their habitat usually occupied along the stream continuum: G. fossarum was an indicator species for the fast-flowing shallow riffles with the dominance of lithal microhabitat, whereas G. roeselii was abundant in the slow-flowing deeper pools usually characterized by vegetation or organic matter. Our results suggest that, beyond the large scale longitudinal distributional pattern and species-specific life-cycles, the meso- and microhabitat characteristics of a stream can drive stable and long-term coexistence among G. fossarum and G. roeselii.

The river Danube is the backbone of the ‘southern invasion corridor’, one of the most important passages for the spread of Ponto-Caspian invaders in Europe. However, not all of these species used the passive or active upstream movement in the main channel to reach the upper sections and tributaries, some found detours. Mass occurrences of the Ponto-Caspian peracarid, Pontogammarus robustoides (Sars, 1894) were recorded at 17 sites along the entire Hungarian section of the River Maros, for the first time in the River Tisza catchment and also in Hungary. Those populations are found ca. 707 km upstream from the closest known and confirmed locality in the lower Danube section. We confirmed their identity by DNA barcoding and showed that all individuals fit in with the lower Danube population, thus identifying the source of this introduction. The most likely vector allowing the jump dispersal of the species is fish stocking in the Romanian section of the River Maros, which − combined with downstream drift to the Serbian Danube section and the relatively busy ship traffic between Belgrade and Vienna − might provide the opportunity to bypass the dispersal barrier represented by the unregulated Middle Danube and open the way towards Western Europe.

Due to the untouched and almost pristine conditions of the Drava region, to date 438 species belonging to various aquatic macroinvertebrate animal groups have been recorded from the Drava and its floodplain. Therefore the aquatic fauna of this area is among the richest in Hungary. The most unique species of the Drava is the caddisfly Platyphylax frauenfeldi, since its population along the river might be the last in the world. The occurrence of many rare, Natura 2000, protected or strictly protected species enhances the nature conservation value of the region. Unfortunately, the large number of non-indigenous species indicates the vulnerability of natural assemblages devastated by aquatic invasions. Moreover, the aquatic macroinvertebrate assemblages are vulnerable, and might be threatened by any unconsidered human action, especially measures of river regulation, since the change or loss of habitats might cause serious damage to the populations of rare species.

Although the sex ratio of Odonata at emergence has received much attention, we are still far from understanding the exact causes of its variability and imbalance. In this paper we studied the sex ratios at emergence in natural populations of two Gomphus species based on samples of exuviae taken from two European lowland rivers. We hypothesized a possible relationship between the water temperature during larval development and the sex ratio at emergence. Sex ratio records exhibited no consistent bias towards one sex but varied between habitats and years in both species. We found correlations between sex ratio and water temperature in the year preceding emergence. Furthermore, the correlation between sex ratios and water temperature was in opposite directions in the two congeneric species, which may be attributed to differences in their voltinisms. We conclude that the effect of water temperature can be mediated through cohort-splitting; temperature-dependent development of minor cohorts, including unequal ...

The spatial variability of Chironomidae larvae assemblages was investigated at 6 near-pristine, temperate headwaters in Hungary. Sites were located within a relatively small mountain range but belong to two different catchment areas characterized by highly variable abiotic conditions. We hypothesised there would be differences in taxonomic composition but not in functional composition between different catchment areas and aimed to assess the primary influencing spatial factors structuring the taxonomic and functional compositions of chironomid assemblages. The spatial distribution of chironomid assemblages was examined 4 times during a 1 year period at microhabitat to catchment scales. At each site, streambed morphology, physicochemical attribute, riparian vegetation, microclimate and hydrology data were collected. Three main traits (saprobic preference, stream zonation preference, functional feeding groups) were used to characterize the functional composition of chironomid assemblages. Sharp differences were detected in taxonomic composition between the two sides of the mountain range within a relatively small spatial distance and moderate, but statistically significant differences in functional composition between catchments. The observed spatial changes in taxonomic and functional composition of midges accompanied changes in physicochemical characteristics, riparian vegetation, microclimate and altitude. Internal microhabitat heterogeneity also played a major role in structuring the taxonomic and the functional patterns of chironomid assemblages.

The Nyirkai-Hany wetland reconstruction area in northwestern Hungary is now designated as a Ramsar and a Natura 2000 site. It was created in 2001–2002 by the Fertő-Hansag National Park Directorate to restore a part of the formerly drained large wetland called Hansag and to offer waterbirds a suitable habitat for feeding and breeding. We focused on this aim of the restoration project and studied the temporal and spatial variation in abundance of birds and their invertebrate prey in this newly created wetland. From April 2007 until May 2008, we sampled plankton, nekton and benthos of different habitats monthly and monitored waterbirds weekly on the three different areas of the Nyirkai-Hany. During our investigations, 135 invertebrate and 53 waterbird species were recorded. Benthos and macrophyte decomposition accelerating guilds were the most abundant waterbird guilds—besides the dominant grazing importer material transporter guild, represented primarily by geese—in the Nyirkai-Hany. Zooplankton assemblages primarily consisted of small species not easily used as a food by planktivorous waterbirds. The low density of zoobenthic biomass and the small extent of shallow water mudflats probably accounted for the scarcity of the bioturbing guild group of birds. Nektonic biomass varied greatly among locations having different vegetation types, was greatest in the shallow water areas dominated by Typha, Carex and Phragmites species and lowest at offshore vegetation-free sites. Chironomids, mayflies and odonates were especially abundant and their biomass significantly correlated with several waterbird species, mainly belonging to the macrophyte decomposition accelerating guild (e.g. Anas platyrynchos, Fulica atra). This guild itself, which has increased in abundance in recent years, showed an exceptionally strong correlation with odonate abundance. These results indicate the growing importance of the Nyirkai-Hany wetland area as a foraging site for waterbirds.

In 2006–2007, spatial variations of chironomid assemblages of a small chalky watercourse were investigated in the hilly region of Balaton Upland, Hungary. Samplings were carried out every three weeks at seven characteristically different sites along the whole length of the watercourse. Altogether 2966 specimens were collected and identified. The chironomid fauna of the stream was relatively rich with 40 taxa belonging to four subfamilies (eight Tanypodinae, one Prodiamesinae, 17 Orthocladiinae, 14 Chironominae). The lowest number of species and number of individuals was found at the spring, and the highest at the middle reach. Based on multivariate analysis the different sections of the creek were characterised by distinctive chironomid communities. Although longitudinal changes in the chironomid community of the Orvenyesi creek were detectable due to changes in natural environmental factors, land-use changes also significantly influenced the chironomid community composition and diversity. The natural and...

The assemblages of aquatic insects are important members of water ecosystems. Based on former studies among the most important factors structuring the assemblages are numerous abiotic ones, such as the sort and the particle size of the substratum. Most of the sampling protocols, e.g. AQEM, determine microhabitats based on those. Nevertheless, we have no information yet about whether or not these different, precisely determined microhabitats have different assemblages. In this study we compared the aquatic insect assemblages of different microhabitat types in three seasons using ADONIS and linear discriminant analyses. We proved that seasonal changes of abiotic factors had a major role in structuring the assemblages. In spring and summer the assemblages differed significantly, however, in autumn no significant differences were found. We supposed that the variation among the assemblages was due to the abundance patterns of frequent species instead of the presence of rare or sparse species. The indicator spe...

In this study we evaluate how variations in taxonomic composition and physical structure of macrophyte stands affect plant-dwelling chironomid assemblages in highly variable macrophyte assemblages in two densely vegetated backwaters. By using multivariate explanatory techniques we found that similar vegetation composition did not unequivocally relate to similar chironomid assemblages, moreover the diversity of macrophyte stands did not correlate with the taxonomic diversity of chironomid assemblages in the backwaters investigated. Taxonomic composition and structural characteristics of the vegetation had little influence on the taxonomic or functional (i.e. feeding groups) composition of chironomid assemblages inhabiting them. Similarly, there are only weak relationships between the distribution of certain chironomid species or functional feeding groups and the environmental variables investigated. In general, the structure of the vegetation was more closely associated with the distribution of dominant chironomid taxa than compositional variables (i.e. density of specific macrophyte taxa). In summary, the structure of aquatic vegetation (i.e. position, size of a stand of vegetation, total plant density) and characteristics of the environment where it develops may be more important in shaping plant-dwelling chironomid assemblages than the taxonomic composition of the vegetation.

Lake Balaton is the largest shallow lake in Central Europe. A large part of its catchment area is a reputable and popular tourism area, where the quality of surface waters is in the center of public and scientific interest. The inflows of Lake Balaton are vulnerable, due to the strong human activity upstream. Despite their significance, the aquatic macroinvertebrate communities of these inflow streams are poorly known. In the summer of 2008, we investigated the distributional pattern of EPT (Ephemeroptera, Plecoptera, Trichoptera) assemblages, and their relationships with selected physico-chemical factors and landscape characteristics at different spatial scales. Samples were taken according to the AQEM sampling protocol at 20 stream sections with different environmental conditions. Multivariate analyses were used for evaluation. Altogether 8131 specimens (6225 Ephemeroptera, 133 Plecoptera, 1773 Trichoptera) belonging to 55 species (25 Ephemeroptera, 2 Plecoptera, 28 Trichoptera) were identified. Cloeon dipterum (L.) and Baetis spp. were the most common mayfly taxa, while caddisfly communities were dominated by limnephilids [Anabolia furcata Brauer, Potamophylax rotundipennis (Brauer)] and hydropsychids [Hydropsyche saxonica McLachlan, H. angustipennis (Curtis)]. The distribution of EPT assemblages was highly affected by pH, conductivity, dissolved oxygen, temperature and total dissolved solids. At reach scale, relationships were detected between spatial patterns of EPT assemblages and structure of riparian vegetation, type of sediment, and some hydromorphological characteristics (e.g., depth and width of stream bed, cover of aquatic vegetation, etc.). At medium and large scale, the ratio of natural and human-impacted areas proved to be the most influential factor.

In 2006–2007 larval caddisfly assemblages of a semi-natural calcareous stream (Örvényesi Creek) were studied. Characteristic sections can be detected along the whole length of the stream, which passes through diverse types of vegetation, resulting in highly heterogeneous aquatic habitats. Based on an annual survey of different aquatic habitats, our aims were to give an overview of the spatio-temporal distribution of the larval caddisfly assemblages in the Örvényesi Creek and to find indicator species characterizing different sections of the stream. In order to show the spatio-temporal patterns, samples were collected at 7 locations with different streambed morphology, from spring to the mouth of the stream. Caddisfly larvae were collected in every 3rd week during a 1 year period using the “kick and sweep” method. Multivariate analyses were carried out to explore the spatio-temporal structure of caddisfly assemblages. The indicator value method was applied to detect indicator species for different sections of the stream. A rich caddisfly fauna (20 taxa) was found in the Örvényesi Creek. Fast-running and relatively cold-water hypocrenal sections were characterized by Beraea maurus and Apatania muliebris at high indicator value. Three Limnephilidae species (Limnephilus rhombicus, Limnephilus lunatus and Glyphotaelius pellucidus) were identified as significant indicator species for slow flowing, lentic habitats. Along the length of the stream, distinctive spatial and temporal changes were detected in the distribution of the caddisfly assemblages. These changes were mainly connected to variations in morphology of the streambed, phenology of individual taxa, extreme weather conditions and human impacts.

Non-biting midges (Chironomidae, Diptera) are widely distributed aquatic insects. The short-living chironomid adults swarm in large numbers above water surfaces, and are sometimes considered a nuisance. They are vectors of certain bacteria, and have a key-role in benthic ecosystems. Optical cues, involving reflection-polarization from water, were found to be important in the habitat selection by three Mediterranean freshwater chironomid species. In this work we report on our multiple-choice experiments performed in the field with several other European freshwater chironomid species. We show that the investigated non-biting midges are positively polarotactic and like many other aquatic insects their females are attracted to horizontally polarized light. Our finding is important in the visual ecology of chironomids and useful in the design of traps for these insects.

Two larvae collected from the River Tisza were recognized to belong to the genus Parasetodes according to the available generic description. The fact that Parasetodes respersellus is the only European/Western Palaearctic representative of the genus enabled us to describe the hitherto unknown larva of this species based on the collected specimens. Diagnostic features to distinguish the genus from other Central European genera are discussed. Possible species-specific characters are compared with those of other previously described species of the genus. Some notes on larval habitat and the European distribution of P. respersellus are given.

Rapid spread of alien and invasive macroinvertebrates across European freshwaters during the last hundred years has caused dramatic changes in structure and function of macroinvertebrate communities, especially in large rivers. Biocontamination of macroinvertebrate communities of Croatian large rivers has been sparsely studied. The aims of this study were to assess the most recent (2015) biocontamination level of macroinvertebrate communities along all four major large rivers in Croatia (Danube, Sava, Drava and Mura) and to establish temporal changes of biocontamination by comparison of our results with previous study. Twenty quantitative samples of 0.0625 m2 in a shallow bank area were collected once in 2015 at 46 sites along the Croatian sections of Danube, Sava, Drava and Mura Rivers using hand nets (mesh size 500 μm). Danube has the highest number of invasive species while Sava and Drava have subset of Danube alien species. The whole Mura River and the most upstream reaches of Drava and Sava in Croatia have not yet been heavily colonized by invasive invertebrates. Sava has been heavily invaded up to ~640 km from the mouth and the main course of Drava up to the last reservoir Donja Dubrava (~250 km from the mouth). The most dominant and widespread invasive species are amphipods Dikerogammarus villosus, D. haemobaphes and two Chelicorophium species, and clams Dreissena polymorpha and Corbicula fluminea. Middle parts of both Sava and Drava have the highest biocontamination level mainly due to high abundance of Chelicorophium spp. and invasive gammarids. Biocontamination levels are mostly stable in Danube and long-time colonized lower and middle parts of Sava and Drava. However, increasing biocontamination levels have been observed in the upstream reaches of Sava and Drava, mostly at the fronts of upstream spreading of invasive gammarids (D. villosus in Drava and D. haemobaphes in Sava). Continuous monitoring of the most invasive species spread and assessment of their impact on macroinvertebrate communities are essential prerequisite for better understanding of the changing ecological state of large rivers.