Alpine areas are extreme habitats that require special adaptations and involve major trade-offs in terms of life history. Amphibians have the ability to adapt both their life history and developmental traits to alpine environments. Temperate amphibians depend on the quality and availability of aquatic habitats for reproduction. We explored the aquatic habitat used by amphibians in the alpine area of Retezat Mountains, Southern Carpathians, Romania. We surveyed 40 aquatic habitats in a 380 ha area delimited by mountain crests and drained by a steep valley. Each aquatic habitat was characterized using 10 environmental variables. Only three amphibian species occur at elevations above 1900 m, the most widespread being the Common Frog Rana temporaria. The Common Frog showed preference for breeding aquatic habitats, the variables of importance being altitude, solar radiation, water chemistry and grazing. Higher elevation and lower solar radiation decreased frog occurrence, while the impact of grazing favored the use of water bodies. Acidification is eminent in the area with pH dropping below 5 in 20% of the water bodies. Overall, amphibian occurrence in alpine area can be partly explained by the characteristics of aquatic habitats.

Fifty years after the hyporheic zone was first defined (Orghidan, 1959), there are still gaps in the knowledge regarding the role of biodiversity in hyporheic processes. First, some methodological questions remained unanswered regarding the interactions between biodiversity and physical processes, both for the study of habitat characteristics and interactions at different scales. Furthermore, many questions remain to be addressed to help inform our understanding of invertebrate community dynamics, especially regarding the trophic niches of organisms, the functional groups present within sediment, and their temporal changes. Understanding microbial community dynamics would require investigations about their relationship with the physical characteristics of the sediment, their diversity, their relationship with metabolic pathways, their interactions with invertebrates, and their response to environmental stress. Another fundamental research question is that of the importance of the hyporheic zone in the global metabolism of the river, which must be explored in relation to organic matter recycling, the effects of disturbances, and the degradation of contaminants. Finally, the application of this knowledge requires the development of methods for the estimation of hydrological exchanges, especially for the management of sediment clogging, the optimization of self-purification, and the integration of climate change in environmental policies. The development of descriptors of hyporheic zone health and of new metrology is also crucial to include specific targets in water policies for the long-term management of the system and a clear evaluation of restoration strategies.

Shredders play a major ecological role in temperate streams, but their numerical importance is highly variable within the tropics. Detailed studies on the diets of tropical stream invertebrates are advisable to be able to better describe and understand this variation. Here, we examined the diets of invertebrates collected from the leaf litter of three tropical streams in Colombia, using gut content analysis. Fine and coarse particulate organic matter were the main food resources for invertebrates, which could be divided into four main dietary groups: predators, shredders, specialist collectors and generalist collectors. While the specialist collectors were the most numerically abundant group (54%), shredder biomass accounted for 63% of total invertebrate biomass, suggesting that shredders play a significant ecological role in the study streams. We describe the diets of 12 out of 47 taxa that were previously unknown, which indicates that knowledge about the feeding ecology of tropical stream invertebrates is still incipient.

The present study evaluated the relative growth and allometry of Massartella brieni Lestage and Thraulodes sp. (Leptophlebiidae: Ephemeroptera). The morphometric analysis was based on 23 measurements and was conducted using a multivariate approach. Throughout postembryonic ontogeny, all of the head measurements, including those of the mouthparts, exhibited negative allometric growth. The mesothorax and wing pad exhibited positive allometric growth. The hind legs lengths in M. brieni and the fore and hind legs lengths in Thraulodes sp. exhibited positive allometry. The abdominal length in these two species exhibited positive allometric growth. Positive allometry was also observed along the abdomen width for M. brieni, and isometry was observed for Thraulodes sp. The relative strengthening of the thorax (in preparation for the winged stage) and the relative increase in the abdomen (which may be related to the development of the reproductive structures) during growth indicate that many of the structures that exhibit positive allometric growth are related to the transition from the aquatic to the adult stage of development.

The relative effects of irradiance and spectral composition on the colonization and development of macroalgal communities were examined in four streams exposed to full sunlight in southern Brazil. A set of solar filters surrounded the artificial substrata to provide various quantitative and qualitative light conditions. In addition to the control, the conditions were full sunlight attenuated by 50, 70 and 90%, blue light (filter transmitting 430–500 nm), green light (500–600 nm) and red light (>600 nm). Macroalgal percent cover was determined three times during the colonization period (15, 39 and 70 days). Significant differences occurred in the mean values for macroalgal community percent cover between treatments at 15 and 39 days, suggesting that early and intermediate stages of the colonization were directly influenced by irradiance. There was an almost complete absence of macroalgae with 90% attentuation, but progressive increases with 70 and 50% attenuation. However, the mean values for macroalgal community percent cover did not differ significantly between color treatments, suggesting that the effects of irradiance on macroalgal colonization were stronger than those of spectral composition at similar intensity. The quantitative responses differed among the taxa.

In contrast to rivers, the effects of water level fluctuations on the biota are severely understudied in lakes. Lake Constance has a naturally pulsing hydrograph with average amplitudes of 1.4 m between winter drought and summer flood seasons (annual flood pulse (AFP)). Additionally, heavy rainstorms in summer have the potential to create short-term summer flood pulses (SFP). The flood pulse concept for lakes predicts that littoral organisms should be adapted to the regularly occurring AFP, i.e. taking advantage of benefits such as an influx of food sources and low predator pressure, though these organisms will not possess adaptations for the SFP. To test this hypothesis, we studied the aquatic invertebrate assemblages colonizing the gravel sediments of Lake Constance, the AFP in spring and a dramatic SFP event consisting of a one meter rise of water level in 24 h. Here, we introduce the term ‘hypolacustric interstitial’ for lakes analog to the hyporheic zone of running water ecosystems. Our results confirm the hypothesis of contrasting effects of a regular AFP and a random SFP indicating that the AFP enhances the productivity and biodiversity of the littoral zone with benthic invertebrates displaying an array of adaptations enabling them to survive. The littoral zones of lakes deliver important ecosystem services by regulating flood effects, producing biomass and supporting biodiversity. To maintain and foster these services, the maintenance or reintroduction of natural water level fluctuations and the conservation of the habitat structures of the hypolacustric interstitial are urgently needed.

The ability of rapid range expansion is one of the key determinants of invasive species success. In order to investigate potential drivers behind the rapid spread of invasive species, we explored changes in population characteristics and structure along the invasion pathway of a successful invader in European freshwaters, the signal crayfish (Pacifastacus leniusculus). Diverse population parameters such as relative population abundance, size and sex structure, differences in morphometry and frequency of injuries were compared between signal crayfish population samples at three uniformly distributed segments (approximately 40 km apart) in the lower section of the Mura River, which differed in time since invasion. Examined signal crayfish populations exhibited notable differences, with more recently established populations toward invasion front characterized by lower abundance and male-biased sex ratios, which highlighted males as initial dispersers. We also recorded significant increase in the relative claw size, a competitively advantageous and allometric trait for males, in more recently established populations away from source population. The recorded differences in population structure and male morphometry along the invasion pathway could lead to important clues about dynamics of range expansion and population establishment, highlighting the traits that promote dispersal and better response to local conditions in new habitats. Established differences can also provide insights into the development of targeted management responses aimed at invasive species control.

We test the possibility of a hybrid origin for Chaetopteryx morettii using cross-breeding experiments and molecular analysis. We show that species within the Chaetopteryx villosa group can hybridize, but that C. moretti is not of hybrid origin. We discuss the applicability of our approach for testing ideas on hybrid speciation and detecting hybrids in natural populations, e.g., for conservation purposes.

Despite their ecological importance and ability to react to environmental changes, including pollution, monogonont rotifers have never been used in palaeolimnological studies because they do not leave subfossil remains. In this study, we tested the possibility of using rotifer resting eggs as a proxy for reconstruction of changes in biodiversity during chronic copper pollution and recovery of a deep sudalpine lake (Lake Orta, Italy). The lake was selected owing to a rich history of previous studies that explored species-specific responses to environmental stressors. Rotifer-based results were compared with those on ephippia and on previously investigated Cladocera subfossil remains. Responses of Rotifera resting eggs to environmental changes were clear and consistent with those previously observed on Cladocera. The abundance of resting eggs increased during pollution, and new morphotypes appeared in addition to those already present. However, overall diversity decreased sharply, as a few morphotypes became dominant. Resting eggs of Brachionus calyciflorus as old as ca. 100 years were still fully viable; viability was not affected by toxic conditions of the environment in which the eggs were produced. Over a period of ca. 80 years, all resting eggs of B. calyciflorus belonged to a single clone, the most widely distributed one in North America. Cladocera ephippia started to accumulate later and at a lower level of abundance than rotifer resting eggs. Overall, Cladocera ephippia were, however, less effective than rotifers in tracing lake historical changes. The results point out at the great potential of using rotifer resting eggs in palaeolimnological reconstructions.

The aim of this research was to investigate three main movement patterns of meiofauna and macrofauna in the riverbed: (1) vertical (downwards) within the interstitial habitat; (2) downstream (negative rheotaxis); (3) upstream (positive rheotaxis). The study was conducted in two headwater streams in the Northern Apennines (Italy), during summer 2009. Sets of traps opening upwards, upstream and downstream to collect, respectively, organisms moving down into the sediment, and organisms with negative and positive rheotaxis, were placed in each sampling site. Benthic samples were collected as well, to compare the benthic community composition with the assemblages colonizing the traps. Meiofauna was the dominant component, representing 95% in benthos and 85% in traps. Vertical top-opened traps collected more taxonomic groups and more individuals of macro- and meiofauna than the horizontal traps, suggesting a dominance of movements deep within the substrate rather than horizontal patterns. Horizontal traps opening upstream (negative rheotaxis) were colonized by more individuals than the traps opening downstream (positive rheotaxis), demonstrating the great importance of movements directed downstream as a primary source of colonization of new areas. Temporary meiofauna (i.e., insect larvae), which was the dominant component of trap assemblages, displayed predominantly vertical movements, supporting the nursery and refuge function of the hyporheic habitat for taxa which spend only the early larval stages in the hyporheos. The results also stress the importance of including meiofauna in studies characterizing the lotic communities.

Excessive sedimentation of fine particles on stream beds has been recognized as a major threat to running-water ecosystems. Deposition of fine sediments often affects hyporheic zone (HZ) functioning by (1) reducing hydrological exchanges at the water–sediment interface and by (2) increasing the organic matter (OM) content of surface sediments. These two factors usually occur concurrently to control biogeochemical processes in sediments. In the present study, experimental and modelling approaches were coupled to evaluate the contribution of these factors on the biogeochemical functioning of the HZ. We used a one-dimensional (1D) vertical model taking into account the hydrodynamic properties, the vertical distribution of the OM and the main microbial processes involved in OM processing (aerobic respiration, denitrification, nitrification and sulphate reduction). This Mobile-Immobile Model for Organic Matter (MIM-OM) model was calibrated and validated using experimental data (conservative tracer, dissolved oxygen and nitrate concentrations) obtained in filtration columns filled with a porous sedimentary matrix. Simulations showed that organic carbon content and Darcy velocity acted in concert to shape biogeochemical processes in stream sediments. The use of the MIM-OM model on data obtained in filtration columns impacted by fine sediment deposition indicated that the biodegradability of the OM (modified through the degradation parameter kPOC) also played a key role on biogeochemical processes occurring in sediments. In conclusion, the MIM-OM model appears as an efficient simulation tool to evaluate biogeochemical functioning in river sediments under different conditions (granulometry, quality of surface water and clogging).

In order to determine the influence of lentic habitats and macrophyte stands on the plankton development and seston flux, an investigation of zooplankton was carried out in the karst Jankovac flow-through system (Papuk Nature Park, Croatia). The system was characterized by low abundance (1–116 ind.L−1) and high diversity of identified zooplankton. Eighty-six taxa were recorded, comprising 57 rotifers, 15 cladocerans, 8 copepods and 6 members of other groups of organisms. The spatial oscillations of environmental parameters and biocoenosis assemblage revealed statistically significant differences between lotic and lentic habitats, as well as between vegetated and non-vegetated stations. These differences mainly respond to higher concentration of food resources and zooplankton/zooseston abundance and biomass in lentic, especially vegetated, habitats. This is also proved by results of principal component analysis (PCA), which suggested that the main drivers of development of the planktonic community were the food resources and the avoidance of flow velocity. Accordingly, shoreline areas with submerged macrophyte stands of Hippuris vulgaris L. were the most productive parts, represented by highest zooplankton abundance, biomass and biodiversity. Flow velocity significantly affected crustaceans assemblage, so that higher abundances of the larger cladocerans and copepods were achieved in vegetated stations with low flow velocity, while rotifers showed to be rheotolerance organisms. On the other hand, the longitudinal discontinuum of the stream channel by two man-made reservoirs could offer new habitats to enrich seston with organic particles and bioseston. The results of our study pronounce the need for further monitoring of this hydrosystem, especially considering biodiversity and microhabitats conservation.

Microcystis blooms occur worldwide in eutrophic lakes. Microcystins (MCs) including microcystin-LR (MC-LR) released by Microcystis have adverse effects on aquatic organisms such as rotifers. To detect population growth and reproductive responses, the rotifer Brachionus calyciflorus was exposed to MC-LR at eight concentrations ranging from 0 to 200 μg.L−1 under different temperature (20, 25 and 30°C), and population growth rate (r), ovigerous females/non-ovigerous females (OF/NOF) ratio, mictic females/amictic females (MF/AF) ratio, mictic rate (MR), and 7-d resting egg (7-d RE) production were investigated. The results showed that higher temperatures stimulate the population growth of B. calyciflorus. B. calyciflorus showed high tolerance to MC-LR at concentrations lower than 200 μg.L−1 under different temperatures. Compared to the control, MC-LR at all concentrations increased the r (P<0.05), but decreased the OF/NOF and the MR of the rotifers at 30°C (P<0.01). A clear dose–response relationship existed between the r, the OF/NOF, and the MR of B. calyciflorus and MC-LR concentration at 30°C, respectively. These sensitive parameters could be used to monitor the ecological effects of low concentrations of MC-LR in natural water bodies at the high temperature.

The diet composition and feeding strategy of native and exotic fish species were studied from May 2005 to February 2006 in three Patagonian low-order streams. A total of 464 fish were caught, which belonged to the exotic species Oncorhynchus mykiss (270), Salmo trutta (177) and the native species Hatcheria macraei (17). The analysis of 336 stomach contents indicated that at the individual level, the three species had a generalized feeding strategy based on benthic invertebrates (Plecoptera, Trichoptera, Coleoptera and Diptera). In the three streams, the widest population niches were observed in winter. There was, however, also a slight tendency toward an increased between-phenotype contribution to the niche width in same season, indicating that a small proportion of individuals within the fish populations specialized by predominantly feeding on a few specific prey species. Hence, the wide population niche widths observed throughout the year were partly a result of mixed individual feeding strategies within the populations. The higher diet overlaps were registered between exotics O. mykiss–S. trutta at Glyn and Carbón, and O. mykiss and the native H. macraei at Manguera, but it changed markedly through the year, perhaps depending on temporal changes in food availability suggesting a competitive coexistence of these species. This is mainly related to the fact that both species changed their food preferences in spring and foraged almost exclusively on Aubertoperla illiesi. This implies that in order to reduce the predation risk or the inter-specific competition for food, the fish species might partition the feeding habitats.

The relative importance of biotic and abiotic variables on the Common Kingfisher Alcedo atthis breeding distribution in northern Iberian rivers was quantified through surveys completed in 2007. Eight rivers were surveyed for “positive” and “negative” (control) breeding territories (PBT and NBT, respectively). PBT (N=9) were 3-km river sections with breeding pairs; NBT (N=8) were 3-km river sections close to PBT, where no pairs were found, with apparently similar features to the PBT and one or more cut banks suitable for nesting. Stepwise discriminant analysis (SDA) correctly classified 94.1% of territories and revealed PBT was associated with higher oxygen concentrations, a lower maximum depth and lower proportion of rockfills. Causes and consequences of these findings are discussed.

Cyanobacteria are a worldwide group of photosynthetic prokaryotes that can cause nuisance blooms in eutrophic waters. It is generally accepted that their resting cells, akinetes, play an important role in the dispersal, recruitment, initiation of blooms and survival under unfavourable conditions, therefore information on the germination, distribution and abundance of akinetes in natural sediments is essential for understanding the ecology and bloom dynamics of N2-fixing cyanobacteria. The present study describes the effect of irradiance on the germination and subsequent growth of N2-fixing filamentous cyanobacteria developed from natural akinete stock in sediment of Lake Balaton (Hungary) with varying phosphorous supply. The research focuses on the invasive Cylindrospermopsis raciborskii and Aphanizomenon flos-aquae the most abundant species of this lake. In the experiments, the germination of ten filamentous N2-fixing cyanobacteria species was observed. The species assemblages of the germinated cyanobacteria populations showed strong light and phosphorus dependence. Anabaena and Anabaenopsis species became dominant in phosphorous-rich conditions, while in phosphorus-deficient environments Aphanizomenon species and C. raciborskii dominated. Among the germinated filaments we have detected Anabaenopsis cunningtonii and Anabaena compacta, which have not been observed in Lake Balaton previously. Our results suggest that among the filamentous heterocytic cyanobacteria of this shallow lake the invasive C. raciborskii was the best competitor when phosphorus supply and irradiance were low.

We evaluated the influence of environmental integrity and the potential as bioindicator of larval stages of species of Trichoptera in 20 streams of first to fourth order in the Pindaíba river basin, Mato Grosso, Central Brazil. We measured stream integrity with the habitat integrity index (HII), establishing three levels of conservation: preserved, altered and impacted environments. We used (i) simple regression to assess the effect of habitat integrity on species abundance of Trichoptera and (ii) the indicator species analysis (IndVal) to assess the potential as bioindicator of each species. We found that 12 morphospecies showed relationship with HII: six species were bioindicators of preserved and two species of altered environments. Morphospecies that showed relationship in the two analyses (i and ii) were considered strong bioindicators, considering that the other species supported higher environmental variation, becoming evident that loss of physical structure reduces the abundance of organisms specialized in preserved environments. The results showed that the distribution and abundance of trichopterans can be an indicator of habitat integrity. Trichopteran species have bioindicator potential, corroborating the hypotheses of this work that abundance of organisms will be smaller in environments with low integrity, and that many species are specific to preserved environments, disappearing from impacted environments, and also characteristic species of altered environments.

Based on a literature survey and the identification of all available collection material, a checklist and distribution maps for the caddisflies occurring in Flanders were prepared. Of the 126 species that have been recorded, 16 are now extinct in Flanders, while the majority of the remaining species is rare and their populations are often vulnerable due to isolation. Caddisflies only occurred at high oxygen levels and relatively low conductivities and three species assemblages could be recognized. A first group of species lived in stagnant waters and those species tolerated slightly lower oxygen concentrations than species characteristic for running waters. In streams of the Campine region, which are characterized by a low pH and a low conductivity, a second group of species was found. The last group of species mainly occurred in the loamy region, where pH and conductivity are higher. Running waters in other ecoregions mainly contained ubiquist species and did not possess a characteristic species assemblage. Despite the fact that the ecological water quality in Flanders slightly increased during the last few decades, the ecological water quality of most waters is still too low for caddisflies. According to the European Union water framework directive, a good ecological water quality should be obtained in all surface waters. Additional measures to improve the water quality are necessary in order to obtain sustainable populations of the caddisfly species occurring in Flanders.

Landscape is important in determining the composition of aquatic assemblage, and benthic invertebrates, particularly Chironomidae, are often used as bioindicators of environmental quality because their occurrence and distribution are influenced by different land uses. The objective of this study was to evaluate the influence of different land uses, considering three landscape scales (drainage basins, riparian buffer and streams), on chironomid assemblage. We sampled streams located in an agricultural matrix by collecting chironomid larvae and water samples and performed a landscape analysis using Geographical Information System techniques. The drainage basins had a high percentage of agricultural land use; in all of the drainage basins studied, 79% of the riparian buffer was not in accordance with Brazilian law. Cricotopus proved to be a good indicator of the agricultural conditions, whereas Thienemanniella and Rheotanytarsus proved to be indicators of exposed soil. Lopescladius was more sensitive to disturbance and was positively correlated with the presence of riparian vegetation. Although the variables at the local scale (stream) were responsible for a major change in the assemblage, the landscape attributes at large scales (drainage basin and riparian buffer) generated significant effects on Chironomidae fauna. Our results suggest the importance of the conservation of two larger landscape scales to support the equilibrium and maintenance of aquatic assemblage.