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Small streams dominate the hydrological network within Europe. In many regions, these waterbodies drain large areas of agricultural land and are vulnerable to pressures linked to livestock management, which can include direct livestock access. This study investigated the impacts of cattle access to watercourses on the contamination of streambed sediment with Escherichia coli (E. coli) in five agricultural catchments. Sediments were collected at cattle access sites and at areas upstream with no cattle access, in two time points in the livestock management cycle (mid-grazing and post-grazing season). Relatively high E. coli concentrations of 103 to 104 CFU g dry wt−1 were found at sites with no access in mid-grazing season. However, concentrations were significantly higher at sites with cattle access. E. coli was present, but in generally lower concentrations, in the post-grazing season. Additionally, the study found a significant negative relationship between the quality of the general riparian environment and E. coli bed sediment concentrations at the cattle access sites in the mid-grazing season, and a significant positive relationship between E. coli concentrations and estimated cattle density locally in post-grazing season. These findings indicate that allowing livestock access to watercourses can have implications for both water quality and human health. [ABSTRACT FROM AUTHOR]

• Long-term Chironomidae response to chemical stressors have been hardly addressed. • Model predicts Chironomidae response across generations, stages, and latitudes. • Emergence reduction stronger with prevalence of early-instar larvae. • Emergence reduction twice as severe in the 2nd year of Bti application. • Model adaptable to other insects, chemicals, latitudes via adjusted parameterisation. Chironomidae are the most abundant aquatic insect group and are important in providing energy and nutrients to aquatic and terrestrial food webs. The stress response of Chironomidae can vary with environmental conditions and time of pollutant exposure, making it difficult to understand the underlying mechanisms. Here, we use a dynamic population model to predict the potential effects of anthropogenic stressors on Chironomus riparius larvae and adult emergence for up to two years. We employed the non-chemical larvicide Bacillus thuringiensis var. israelensis (Bti) as a case study, as this stressor has been shown to reduce larval survival of C. riparius. To predict the responses of C. riparius adapted to variable geographic conditions, we simulated scenarios in which Bti is applied at three different latitudes in Europe. For each latitude, we also simulated a varying Bti application timing corresponding to a higher or a lower density of early-instar larvae, for which a higher sensitivity to Bti is documented. While acute exposure to Bti did not alter the patterns of larval development and adult emergence, in all scenarios and latitudes considered, the predicted reduction was stronger when Bti was applied to populations with a prevalence of early-instar larvae. Moreover, in all simulated scenarios, the reduction in the second year of Bti application was approximately twice as large as in the first year, revealing cumulative effects. Our model can be used to develop new hypotheses and test them through either empirical or in silico experiments to project the long-term effects of Bti on Chironomidae populations. The model can be theoretically applied to other insect groups and toxicants, and to different latitudinal scenarios by changing input parameters. [ABSTRACT FROM AUTHOR]

Ranunculus species grouped in the section Batrachium (water crowfoots) indicate the most valuable fluvial habitat in Europe under the EU Habitats Directive, and recognition of their environmental preferences plays a crucial role in efficient conservation. Moreover, water crowfoots are used in various monitoring systems throughout Europe. The aim of this study was to identify the distribution patterns of two common water crowfoot species (Ranunculus fluitans, R. circinatus) and their hybrid (R. circinatus × R. fluitans) in relation to environmental variables in rivers. Various chemical and hydromorphological parameters were estimated for 54 river sites where 58 different Batrachium populations were recorded. Our study revealed the most distinct positive reaction of R. fluitans to rhithral conditions characterized by rapid currents and coarse substrate. R. circinatus × R. fluitans preferred larger channels, although this taxon also flourished in rhithral rivers. The preferences of R. circinatus were not so evident confirming its occurrence under a wide range of habitat conditions. The ecological reaction of the hybrid was compared with its parental species, revealing their ecological specificity, which is useful in designing appropriate conservation programmes. [ABSTRACT FROM AUTHOR]

An extensive macrophyte field survey of running and standing waters was conducted from 2016 to 2021 at 786 sampling sites across Croatia as a part of the implementation of the Water Framework Directive. This survey is the first to present a comprehensive floristic catalogue of the freshwater bryoflora, along with an analysis of the distribution and diversity patterns on a national level. In all, 83 bryophyte species (68 mosses and 15 liverworts) were recorded in the 228 sites, with average species richness of 4.17 species per site. The most frequent species were Fontinalis antipyretica, Rhynchostegium riparioides, Leptodictyum riparium and Cratoneuron filicinum. The majority of the species encountered were rarely found, with over 70% of species recorded on less than 10 sampling sites and the majority of the species not being truly aquatic, rather being classified as facultative aquatics. The Dinaric Ecoregion, characterised by clean, cold, fastflowing karstic rivers, especially in the Continental Subecoregion, supported higher freshwater bryophyte diversity than the lowland Pannonian Ecoregion, with mostly slow, eutrophic lowland watercourses with unstable sandy and gravelly alluvial sediments. Chorological comparison of Croatian eco- and subecoregions revealed the expected dominance of circumpolar and European elements, i.e. temperate chorotypes, as well as some biogeographical differences. The most frequent life forms were aquatic trailings and turfs. Amongst the recorded species, perennials and colonists were the most represented life strategies. The analysis of both the life-form and life-strategy spectra showed some differences amongst the Croatian regions, supporting the fact that the Dinaric Ecoregion provides more truly aquatic habitats and microhabitats suitable for the freshwater bryophytes, while in the Pannonian Ecoregion freshwater bryophytes dominantly inhabit the periodically submerged riparian zones, for example shaded lowland forest streams and rivulets or gently sloping margins of rivers and lakes. [ABSTRACT FROM AUTHOR]

Intermittent rivers are prevalent in many countries across Europe, but little is known about the temporal evolution of intermittence and its relationship with climate variability. Trend analysis of the annual and seasonal number of zero-flow days, the maximum duration of dry spells and the mean date of the zero-flow events is performed on a database of 452 rivers with varying degrees of intermittence between 1970 and 2010. The relationships between flow intermittence and climate are investigated using the standardized precipitation evapotranspiration index (SPEI) and climate indices describing large-scale atmospheric circulation. The results indicate a strong spatial variability of the seasonal patterns of intermittence and the annual and seasonal number of zero-flow days, highlighting the controls exerted by local catchment properties. Most of the detected trends indicate an increasing number of zero-flow days, which also tend to occur earlier in the year, particularly in southern Europe. The SPEI is found to be strongly related to the annual and seasonal zero-flow day occurrence in more than half of the stations for different accumulation times between 12 and 24 months. Conversely, there is a weaker dependence of river intermittence with large-scale circulation indices. Overall, these results suggest increased water stress in intermittent rivers that may affect their biota and biochemistry and also reduce available water resources. [ABSTRACT FROM AUTHOR]

The relationship between River Ammer flood frequency variability, extreme summer climate over Europe, and solar forcing is investigated. First, we used observational data to evaluate extreme weather and climate anomaly patterns associated with flood and solar forcing as well as the possible dynamical mechanisms behind them. Then, the annual resolution flood layer record from the Lake Ammer sediments is analysed to evaluate millennial‐scale variability of floods and possible related extreme climate patterns back to 5,500 years BP. A composite analysis reveals that observed River Ammer flood frequency variability at interannual to multidecadal time scales is connected to large‐scale extreme precipitation and temperature patterns. From a synoptic‐scale perspective, the extreme precipitation pattern associated with floods is related to an increase in the frequency of high upper‐level potential vorticity (PV) events over western Europe and a decrease over eastern Europe and western Russia. Increased (decreased) frequency of upper‐level high PV events is related to more (less) surface extreme precipitation occurrence. Furthermore, we show that increased frequency of upper‐level high PV events over western Europe is associated with enhanced blocking activity over eastern Europe. Therefore, the out of phase interannual to millennial‐scale variations of River Ammer flood frequency and solar irradiance, as presented in previous studies, can be explained by a solar modulation of eastern European‐western Russia summer blocking and associated upstream upper‐level wave breaking activity. In addition, we identify two distinct quasi‐periodic signals in both frequency of Lake Ammer flood layer and solar irradiance records with periods of ~900 years and ~2,300 years. We argue that similar cycles should dominate millennial‐scale variations of blocking activity in eastern Europe‐western Russia as well as extreme precipitation and flood frequency variability over central and western Europe during the last ~5,500 years. [ABSTRACT FROM AUTHOR]

Over the past decades, Europe has been affected by several low flow periods which had substantial impacts on the hydrology of the rivers themselves as well as on the society and economy. Low flow periods have a direct impact on the environment, on the inland waterway navigation, on the hydropower production as well as on the sediment management, among others. Similar to floods, low flows are naturally occurring phenomena which can significantly hinder different uses and functions of the rivers and impact the aquatic system and the water quality. Moreover, it is projected that, in the future, climate change might lead to drier summers over the European region and therefore to more frequent and severe low flow periods. The results presented here show that the summer 2018 low flow situation, over the Rhine and Elbe Rivers basin, could have been predicted up to two seasons ahead by using previous months' sea surface temperature, sea level pressure, precipitation, mean air temperature and soil moisture. The lagged relationship between the predictand (e.g. seasonal streamflow) and the climate and oceanic predictors varies between 1 month (e.g. precipitation) up to 6 months (e.g. sea surface temperature). Taking into account that all predictors are available in real-time, the forecast scheme can be used to provide early warnings for the upcoming low flow situations, thus offering the possibility for better management of the water resources. [ABSTRACT FROM AUTHOR]

Recent climatic changes have the potential to severely alter river runoff, particularly in snow-dominated river basins. Effects of changing snow covers superimpose with changes in precipitation and anthropogenic modifications of the watershed and river network. In the attempt to identify and disentangle long-term effects of different mechanisms, we employ a set of analytical tools to extract long-term changes in river runoff at high resolution. We combine quantile sampling with moving average trend statistics and empirical mode decomposition and apply these tools to discharge data recorded along rivers with nival, pluvial and mixed flow regimes as well as temperature and precipitation data covering the time frame 1869–2016. With a focus on central Europe, we analyse the long-term impact of snow cover and precipitation changes along with their interaction with reservoir constructions. Our results show that runoff seasonality of snow-dominated rivers decreases. Runoff increases in winter and spring, while discharge decreases in summer and at the beginning of autumn. We attribute this redistribution of annual flow mainly to reservoir constructions in the Alpine ridge. During the course of the last century, large fractions of the Alpine rivers were dammed to produce hydropower. In recent decades, runoff changes induced by reservoir constructions seem to overlap with changes in snow cover. We suggest that Alpine signals propagate downstream and affect runoff far outside the Alpine area in river segments with mixed flow regimes. Furthermore, our results hint at more (intense) rainfall in recent decades. Detected increases in high discharge can be traced back to corresponding changes in precipitation. [ABSTRACT FROM AUTHOR]

Climatic oscillations occurring during the Pleniglacial and Lateglacial periods are generally associated with several changes in fluvial morphology and processes. This study investigated two reaches of the Cher River basin (Noyers-sur-Cher and Thénioux) regarding morphological adjustments during the Lateglacial period and the early Holocene. Transitions from the Pleniglacial to the Lateglacial and from the Lateglacial to the early Holocene (ca. 14,700–11,500 cal. BP) are considered as interesting study cases because it consists of rapid and abrupt climate oscillations generally clearly recorded in current floodplains. The sites studied are located in the Cher River floodplain, which is one of the main tributaries of the Loire River. Several investigations have been conducted in the main valley, but few of them specifically focused on geomorphological evolutions of medium-sized catchments such as tributaries of the Loire River. Therefore, we examined this specific period through investigations recently conducted in the middle valley of the Cher River. This study aimed to (1) provide a geomorphological approach to fluvial adjustments during the Lateglacial from cases located in lowland areas of a medium-sized basin and (2) analyse the spatio-temporal variability of fluvial responses. Assessment of geomorphological trajectories of the two reaches studied highlights that fluvial metamorphosis occurring during the Lateglacial and early Holocene seems to be characterised by lateral readjustments and a low signal of morphological instability (shallow incision and aggradation processes, slow and progressive change in channel morphology). This observation is enhanced by the comparison with known geomorphological evolution patterns of adjacent basins. The intrinsic components of the Cher basin such as slope and valley width were considered as explanatory factors for the lack of morphogenetic processes. In addition, the geographical location of the reaches studied may also have led to a moderated expression of climate forcing. Indeed, the elevation as well as the north– south and east–west gradients may contribute to the low level of geomorphological adjustments in response to these climatic oscillations. This gradient could also have support this the fluvial response because of the weakly developed loess cover, which may have limited the fine sediment supply and the aggradation of the valley bottom. [ABSTRACT FROM AUTHOR]

We comparatively examined the role of littoral and deep water sampling methods in assessing macroinvertebrate assemblages and in characterizing longitudinal changes in assemblage structure along >2,500‐km–long course of the Danube River, Europe. The effectiveness of detecting taxa corresponded well with an inshore–offshore gradient in sampling (i.e., distance from shore). Nevertheless, each method (i.e., littoral multihabitat sampling, kick and sweep sampling, and deep water dredging) contributed to some degree to overall taxa richness and species composition. Sampling in different depth zones characterized different assemblages, and consequently, inshore–offshore position was at least as important determinant of assemblage structure as longitudinal position of sampling sites in the river. Although we found significant congruency in the spatial variability of assemblages among the sampling methods, the relationships were only moderate. Our study on the large Danube River confirms studies from smaller rivers in other geographic regions that littoral monitoring provides higher taxa richness and more responsive changes to longitudinal gradients than deep water samples. Nevertheless, it also shows that sampling in different depth zones provides supplementary information on assemblage structure. Understanding changes in macroinvertebrate assemblages related to differences in sampling method is crucial to improve the bioassessment and environmental management of large rivers. [ABSTRACT FROM AUTHOR]

Multi-channel rivers support diverse and productive ecological communities, and their rareness in the developed world places a great importance on their conservation. The design of side channel restoration projects remains poorly informed by theory or empirical observations. One of the last examples of anastomosing rivers in Europe is a stretch of River Narew in Poland protected as a national park. Park Authorities face a problem of side channels extinction in last few decades and therefore a dedicated plan of protection measures (submerged weir construction, dredging and mowing of side channels) was established aimed at anastomosing system conservation. The objective of this study was an ex-ante assessment of the impact of proposed protection measures on discharge distribution, flow velocity and sediment transport potential in the anastomosing section of the river, using a hydraulic, one-dimensional model. Among the tested measures, more invasive dredging and damming were significantly more efficient than less invasive vegetation removal. Compared to other restoration projects of multi-channel rivers (Narew and Rhône cases), supported by extensive post-restoration monitoring, efficiency level was comparable reaching on maximum tenfold increase in discharge and fivefold increase in reach-averaged flow velocity in restored side channels. Post-conservation alterations of hydraulic properties in the anabranches resulted in a significant increase in sediment transport potential for measures changing channel geometry. Such change could potentially ensure the stability of restoration eliminating the main cause of channels extinction i.e. excessive sediment deposition. [ABSTRACT FROM AUTHOR]

The metabolism of forest streams depends on the decomposition of plant litter of terrestrial origin. In turn, the rate at which litter decomposes depends on litter characteristics, decomposer activity, environmental characteristics, and their interactions. Atmospheric changes, such as increases in atmospheric carbon dioxide concentration ([CO2]) and in temperature, may affect all these variables. Here, we report the results of a meta‐analysis of 41 studies conducted worldwide between 1993 and 2017 on the effects of elevated atmospheric [CO 2], elevated temperature, or both (temperature + [CO 2]) on litter decomposition in streams. Elevated temperature significantly increased litter decomposition rates, whereas elevated [CO 2] and temperature + [CO 2] did not significantly affect litter decomposition rates. The effect of elevated temperature did not depend on the type of study (i.e., laboratory or field study, correlative field or manipulative field study) but in correlative field studies, the temperature effect was stronger over latitudinal than altitudinal gradients. Effects of elevated temperature also did not depend on the type of decomposer community (microbial or microbial and macroinvertebrates) but effects were always significant for total litter decomposition (both microbes and macroinvertebrates involved), whereas microbial‐driven litter decomposition was significantly affected only in manipulative studies. Effects of elevated temperature did not depend on the litter identity, although significant effects were found for some litter genera but not others. In terrestrial ecosystems, the elevated temperature was found to increase litter decomposition rates, whereas elevated [CO 2] decreased litter decomposition rates. Study type (laboratory or field) and litter identity were important moderators of the response of litter decomposition to elevated temperature and [CO 2] in terrestrial ecosystems. These differences between soil and stream ecosystems may be partially due to intrinsic differences (such as moisture that is not limiting in streams) between these ecosystems. In addition, our meta‐analysis is geographically biased with most studies being conducted in Europe. More studies in other parts of the world could allow for a better understanding of the effects of climate warming and [CO 2] increases on litter decomposition, the global carbon cycle, and biochemistry in streams. [ABSTRACT FROM AUTHOR]

The European Union's Water Framework Directive introduced a new approach to the system of water management in Europe by nominating the river basin district as the basic unit in water management. While its transboundary character aims to better manage natural resources, its design and implementation carries several challenges due to its weak integration of various bordering effects related to administrative boundaries that strongly affect the directives' implementation. Based on a comparative document based case study of two river basin districts – the International Oder River Basin District (IORBD) and the International Torne River Basin District (ITRBD) – the paper scrutinizes the effects on the implementation processes of the directive and aims to draw attention to identify the differences that derive from various socio-spatial settings during the first cycles of water management plans from 2009 to 2015. By thematically comparing biophysical characteristics, cross-border cooperation, cultural and administrative bordering processes the study displays a mismatch between the directives aims for transboundary governance and the actual governance processes which are hampered by a variety of conflicting bordering processes. [ABSTRACT FROM AUTHOR]

For understanding hydroclimatological process chain it is crucial to identify relations between largescale climatic circulations and river discharge. The Danube is one of the most important European waterways, flowing 2.857 kilometers across the Europe and with 817.000 km2 basin. Danube River average and maximum discharges are correlated with eight atmospheric circulation patterns indices: AOi, EAi, EA/WRi, ENSOi, MOi, NAOi, SCANDi and WeMOi in 65 years period at the Bezdan gauging station in Serbia. Obtained results showed that precipitation, MOi and WeMOi have constant and dominant influences on Danube River average discharge at Bezdan gauging station, while maximum discharge is mainly influenced by precipitation and MOi. All registered correlations are positive. [ABSTRACT FROM AUTHOR]

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This study examines a selection of river confluences, places that are frequently locations of important physical investigations by hydrologists, geomorphologists, biologists, and engineers, among others. In contrast, confluences can also demonstrate a complex interplay of historical, economic, social, and political factors. Many urban stream confluences were sites of prehistoric human settlement; others are more recent historic sites, or important shipping facilities; and some are simply tourist attractions. From the multitude of stream confluences, this paper examines a small selection from the United States of America and Europe, with a focus on the multiplicity of human associations and layers of meaning. [ABSTRACT FROM AUTHOR]

Rivers are a vital resource for human wellbeing. To reduce human impact on water bodies, the European Union has established an essential regulatory framework for protection and sustainable management (WFD; 2000/60/EC). In this strategy, reliable and economic bioindicators are a fundamental component. Benthic macroinvertebrates are the group most commonly used as bioindicators through all European countries. However, their conventional assessment currently entails serious cost-efficiency limitations. In this study, we have tested the reliability of metabarcoding as a tool to record river macroinvertebrates using samples from a mock community (in vitro validation) and eDNA extracted for field validation from water from six sites within a north Iberian river (River Nalón, Asturias, Spain). Two markers (V4 region within the nuclear 18S rDNA and a fragment of the mitochondrial COI gene) were amplified and sequenced using an Illumina platform. The molecular technique has proven to be more sensitive than the visual one. A cost-benefit analysis shows that the metabarcoding approach is more expensive than conventional techniques for determining macroinvertebrate communities but requires fewer sampling and identification efforts. Our results suggest metabarcoding is a useful tool for alternative assessment of freshwater quality. [ABSTRACT FROM AUTHOR]

European large rivers are exposed to multiple human pressures and maintained as waterways for inland navigation. However, little is known on the dominance and interactions of multiple pressures in large rivers and in particular inland navigation has been ignored in multi-pressure analyzes so far. We determined the response of ten fish population metrics (FPM, related to densities of diagnostic guilds and biodiversity) to 11 prevailing pressures including navigation intensity at 76 sites in eight European large rivers. Thereby, we aimed to derive indicative FPM for the most influential pressures that can serve for fish-based assessments. Pressures' influences, impacts and interactions were determined for each FPM using bootstrapped regression tree models. Increased flow velocity, navigation intensity and the loss of floodplains had the highest influences on guild densities and biodiversity. Interactions between navigation intensity and loss of floodplains and between navigation intensity and increased flow velocity were most frequent, each affecting 80% of the FPM. Further, increased sedimentation, channelization, organic siltation, the presence of artificial embankments and the presence of barriers had strong influences on at least one FPM. Thereby, each FPM was influenced by up to five pressures. However, some diagnostic FPM could be derived: Species richness, Shannon and Simpson Indices, the Fish Region Index and lithophilic and psammophilic guilds specifically indicate rhithralisation of the potamal region of large rivers. Lithophilic, phytophilic and psammophilic guilds indicate disturbance of shoreline habitats through both (i) wave action induced by passing vessels and (ii) hydromorphological degradation of the river channel that comes along with inland navigation. In European large rivers, inland navigation constitutes a highly influential pressure that adds on top of the prevailing hydromorphological degradation. Therefore, river management has to consider river hydromorphology and inland navigation to efficiently rehabilitate the potamal region of large rives. [ABSTRACT FROM AUTHOR]

The Austrian network of isotopes in rivers comprises about 15 sampling locations and has been operated since 1976. The Danube isotope time series goes back to 1963. The isotopic composition of river water in Central Europe is mainly governed by the isotopic composition of precipitation in the catchment area; evaporation effects play only a minor role. Short-term and long-term isotope signals in precipitation are thus transmitted through the whole catchment. The influence of climatic changes has become observable in the long-term stable isotope time series of precipitation and surface waters. Environmental 3H values were around 8 TU in 2015, short-term 3H pulses up to about 80 TU in the rivers Danube and March were a consequence of releases from nuclear power plants. The complete isotope data series of this network will be included in the Global Network of Isotopes in Rivers database of the International Atomic Energy Agency (IAEA) in 2017. This article comprises a review of 50 years isotope monitoring on rivers and is also intended to provide base information on the (isotope-)hydrological conditions in Central Europe specifically for the end-users of these data, e.g. for modelling hydrological processes. Furthermore, this paper includes the 2006-2015 supplement adding to the Danube isotope set published earlier. [ABSTRACT FROM AUTHOR]

In this study the occurrence of thresholds in fluvial style changes during the Holocene are discussed for three different catchments: the Dijle and Amblève catchments (Belgium) and the Valdaine Region (France). We consider tipping points to be a specific type of threshold, defined as relatively rapid and irreversible changes in the system. Field data demonstrate that fluvial style has varied in all three catchments over time, and that different tipping points can be identified. An increase in sediment load as a result of human induced soil erosion lead to a permanent change in the Dijle floodplains from a forested peaty marsh towards open landscape with clastic deposition and a well-defined river channel. In the Valdaine catchment, an increase in coarse sediment load, caused by increased erosion in the mountainous upper catchment, altered the floodplains from a meandering pattern to a braided pattern. Other changes in fluvial style appeared to be reversible. Rivers in the Valdaine were prone to different aggradation and incision phases due to changes in peak water discharge and sediment delivery, but the impact was too low for these changes to be irreversible. Likewise the Dijle River has recently be prone to an incision phase due to a clear water effect, and also this change is expected to be reversible. Finally, the Amblève River did not undergo major changes in style during the last 2000 to 5000 years, even though floodplain sedimentation rates increased tenfold during the last 600 years. Overall, these examples demonstrate how changes in fluvial style depend on the crossing of thresholds in sediment supply and water discharge. Although changes in these controlling parameters are caused by anthropogenic land use changes, the link between those land use changes and changes in fluvial style is not linear. This is due to the temporal variability in landscape connectivity and sediment transport and the non-linear relationship between land use intensity and soil erosion. [ABSTRACT FROM AUTHOR]

Rivers extend in space and time under the influence of their catchment area. Our perception largely relies on discrete spatial and temporal observations carried out at certain sites located throughout the catchment (monitoring networks, MN). However, MNs are constrained by (a) the distribution of sampling sites, (b) the dynamics of the variable considered and (c) the river hydrological conditions. In this study, all three aspects were captured and quantified by applying a spatial autocorrelation modeling approach. We exemplarily studied its application to 235 emerging contaminants (pesticides, pharmaceuticals, and personal care products [PPCP], industrial and miscellaneous) measured at 55 sampling sites in the Danube River. 22 out of the 235 compounds monitored were present at all sites and 125 were found in at least 50%.We first calculated the Moran Index (MI) to characterize the spatial autocorrelation of the compound set. 59 compounds showed MI ≤ 0, which can be interpreted as ‘no spatial correlation’. Next, spatial autocorrelation models were set for each compound. From the autocorrelation parameter ρ , catchment average correlation lengths were derived for each compound. MN optimality was examined and compounds were classified into three groups: (a) those with ρ ≤ 0 [25%]; (b) those with ρ > 0 and correl. length < average distance between consecutive sites [ 2%] and (c) those with ρ > 0 and correl. length > average distance between consecutive sites [73%]. The MN was considered optimal only for the latter class. Networks with the larger average distance between consecutive sites resulted in a decreasing number of optimally monitored compounds. Furthermore, neighbors vs . local relative contributions were quantified based on the spatial autocorrelation model for all the measured compounds. The results of this study show how autocorrelation models can aid water managers to improve the design of river MNs, which are a key aspect of the Water Framework Directive. [ABSTRACT FROM AUTHOR]

Habitat connectivity crucially influences dispersal of organisms. It is especially seen as an important driver of the spatial structuring of biological communities in ecosystems that have intrinsic and general connectivity patterns, such as the universal dendritic structure of fluvial networks. These networks not only define dispersal of native species, but also represent corridors of biological invasions, making understanding network topology effects on invasion dynamics and subsequent diversity patterns of high interest. We studied amphipod community diversity and structure in the upper 27,882-km² drainage basin of the river Rhine in Central Europe, focusing on differences between native and non-native species. Overall, species richness increased along the network from headwaters to the outlet nodes. We found, however, contrasting patterns of native and non-native amphipod richness along the network, with headwater nodes representing refugia for native species and more downstream nodes being hotspots of biological invasions. Importantly, while species turnover (b-diversity) of native species increased with distance between nodes in the network, this was not the case for non-native species, indicating a much lower dispersal limitation of the latter. Finally, the overall amphipod community structure closely mirrored the topological modularity of the network, highlighting the network's imprint on community structure. Our results underpin the importance of connectivity for community formation and the significance of rivers for biological invasions and suggest that empirically observed matches of diversity patterns in rivers predicted by null models are the long-term outcome of species invasions and species sorting. [ABSTRACT FROM AUTHOR]

Fishes serve as indicators in ecological assessments of European large rivers. Electrofishing is the standard fishing method although it is restricted to the shallow littoral shoreline. Fish occurring in the open water zone of the main channel remain consequently underestimated. Additional sampling methods that cover the mid-channel of rivers could close the electrofishing-gap, but strengths’, weaknesses and gains of both electrofishing and additional sampling methods for fish-based assessments of large rivers have not been contrasted yet. We analyzed a unique dataset consisting of 2693 fish samplings in European large rivers and compared electrofishing with the additional sampling methods trawling, seining, and drift-netting. We compiled fish metrics commonly used in fish-based assessments yielded by the different gears and highlight the differences in fish species, biodiversity metrics (Shannon Index, Evenness, Simpson Index), the Fish Region Index (FRI) and densities of fish in selected guilds (eurytopic, rheophilic, lithophilic, phytophilic, psammophilic, potamal) that are considered indicative for the degradation of habitats in large rivers. Electrofishing yielded overall highest numbers of species, biodiversity metrics and densities of fish guilds, except for the number of migratory and Habitat Directive species, the FRI and densities of potamal fish. The additional gears, predominantly trawling, captured additional rheophilic and lithophilic species. Trawling also assessed most migratory and Habitat Directive species and yielded higher densities of potamal fish as well as larger fish than electrofishing. Trawl catches further estimated higher biodiversity compared to seining, while the latter yielded higher densities of eurytopic, rheophilic, lithophilic and phytophilic fish. Drift-netting yielded the lowest estimates overall but sample size was very low. We suggest that electrofishing is an appropriate method to assess and evaluate the effects of hydromorphological degradation and rehabilitation on fish, and to guide river management. It sufficiently well represents the typical fish assemblage of large rivers despite its restriction to the shoreline. In contrast, assessing specifically Habitat Directive, migratory and rare species, as well as obtaining complete species inventories, e.g., for biodiversity assessments, requires complementary sampling of the mid-channel of large rivers by additional gears such as trawling. [ABSTRACT FROM AUTHOR]

The Morphological Quality Index (MQI) and the Morphological Quality Index for monitoring (MQIm) have been applied to eight case studies across Europe with the objective of analyzing the hydromorphological response to various restoration measures and of comparing the results of the MQI and MQIm as a morphological assessment applied at the reach scale, with a conventional site scale physical-habitat assessment method. For each restored reach, the two indices were applied to the pre-restoration and post-restoration conditions. The restored reach was also compared to an adjacent, degraded reach. Results show that in all cases the restoration measures improved the morphological quality of the reach, but that the degree of improvement depends on many factors, including the initial morphological conditions, the length of the restored portion in relation to the reach length, and on the type of intervention. The comparison with a conventional site scale physical-habitat assessment method shows that the MQI and MQIm are best suited for the evaluation of restoration effects on river hydromorphology at the geomorphologically-relevant scale of the river reach. [ABSTRACT FROM AUTHOR]

The Sava River Basin is a major drainage basin of southeastern Europe, significantly influenced by anthropogenic activities. Our study was focused on diatom communities as an indicator of the ecological status of running waters. We investigated over 937 km of the Sava River at 19 sampling sites. Benthic diatom communities and 17 diatom indices were analyzed along with a large set of environmental parameters. CCA revealed that the most important elements along the spatial gradient were As and Si. Our results show that the species Navicula recens (Lange-Bert.) Lange-Bertalot and Eolimna minima (Grunow) Lange-Bertalot are very abundant at downstream localities where the highest concentrations of As were measured. The number of motile diatoms increased along the nutrient gradient, i.e. with Si availability. Correlations between diatom indices and selected environmental factors showed that temperature, As, Si and Fe are in significant negative correlation with most diatom indices. Analysis revealed the influence of As and metals in water on diatoms, although their concentrations did not exceed environmental standards. While our findings do not confirm that diatom indices reveal the intensity of pressures solely caused by nutrient and/or organic pollutants, they suggest that in moderately polluted large rivers benthic diatoms are good bioindicators of multiple pressures, and that diatom indices could serve as indicators of the level of overall degradation of an ecosystem. [ABSTRACT FROM AUTHOR]

This paper briefly discusses the assessment of hydropower resources (mainly, Small Hydropower, SHP) in the light of general methodologies of renewable energy potential, highlighting the particularities of hydropower. A short review of the EU Water Framework Directive (WFD) from the hydropower development perspective is provided, especially focusing on the impact of power plant pre-planning mechanisms whereby rivers or their reaches are listed as exempt from damming (so-called ‘no go areas’). The hydropower regulation (for prospective hydropower schemes) in the country is critically reviewed, and the current state of the drafting of river basin management plans is presented. Practically speaking, the national water law does not guarantee a declared statement of sustainable use of water resources because of the introduced list of protected rivers exempt from dam construction. In a number of multipurpose water resource development projects that override public interests, e.g., inland navigation and historic water mills, power generation is a secondary service unable to be implemented, due to on the list of protected rivers. In this paper, based on the geospatial datasets of water streams and their environmental attributes, three pre-planning levels for hydropower development are proposed, and the environmentally compliant potential of the SHP is identified. The remaining SHP potential (117 GWh/year or close to 6% of the gross theoretical potential) is among the lowest ones in the EU. The disproportionate environmental constraints in Lithuania are a key factor preventing the development of hydropower and the multipurpose use of water resources. [ABSTRACT FROM AUTHOR]

Climate change and river regulation are negatively impacting riparian vegetation. To evaluate these impacts, process-based models are preferred over data-driven approaches. However, they require extensive knowledge about ecohydrological processes. To facilitate the implementation of such process-based models, the key drivers of riparian woodland successional pathways across three river reaches, in Austria, Portugal, and Spain, were explored, employing two complementary approaches. The principal component analyses highlighted the importance of the physical gradients determining the placement of the succession phases within the riparian and floodplain zones. The generalized additive models revealed that the initial and pioneer succession phases, characteristic of the colonization stage, appeared in areas highly morphodynamic, close in height and distance to the water table, and with coarse substrate, whereas elder phases within the transitional and mature stages showed incremental differences, occupying less dynamic areas with finer substrate. The Austrian site fitted well the current successional theory (elder phases appearing sequentially further up and distant), but at the Portuguese site, the tolerance of the riparian species to drought and flash flood events governed their placement. Finally, at the Spanish site, the patchy distribution of the elder phases was the remnants of formative events that reshaped the river channel. These results highlight the complex relationships between flow regime, channel morphology, and riparian vegetation. The use of succession phases, which rely on the sequential evolution of riparian vegetation as a response to different drivers, may be potentially better reproducible, within numerical process-based models, and transferable to other geographical regions. [ABSTRACT FROM AUTHOR]

Hydromorphological stream assessment has significantly expanded over the last years, but a need has emerged from recent reviews for more comprehensive, process-based methods that consider the character and dynamics of the river with greater accuracy. With this as a focus, a series of hydromorphological tools have been developed and/or further extended in Europe within the context of the REFORM (REstoring rivers FOR effective catchment Management) project. The aim of this paper is to present the set of REFORM hydromorphological assessment methods and, based on some examples of their application, to illustrate and discuss their synergic use, specific features, limitations and strengths. This assessment and monitoring includes three tools: the Morphological Quality Index (MQI), the Morphological Quality Index for monitoring (MQIm), and the Geomorphic Units survey and classification System (GUS). These tools constitute the assessment phase of an overall multi-scale, process-based hydromorphological framework developed in REFORM. The MQI is aimed at an assessment, classification and monitoring of the current morphological state; the MQIm aims at monitoring the tendency of morphological conditions (enhancement or deterioration); the GUS provides a characterization, classification and monitoring of geomorphic units. A series of examples are used to illustrate the potential range of application, including: (i) an assessment of morphological conditions; (ii) an assessment of the morphological effects of restoration projects; (iii) an evaluation of the geomorphic impacts of interventions for risk mitigation; and (iv) an integrated use of MQI and GUS to assess and characterise morphological conditions. Finally, some of the main features, strengths and peculiarities of the three hydromorphological tools are discussed with the support of examples of their application. [ABSTRACT FROM AUTHOR]

River restoration is a main emphasis of river management in European countries. Cross-national comparisons of its implementation are still rare in scientific literature. Based on French and German national censuses, this study compares river restoration practices and monitoring by analysing 102 French and 270 German projects. This comparison aims to draw a spatial and temporal framework of restoration practices in both countries to identify potential drivers of cross-national similarities and differences. The results underline four major trends: (1) a lag of almost 15 years in river restoration implementation between France and Germany, with a consequently higher share of projects in Germany than in France, (2) substantial similarities in restored reach characteristics, short reach length, small rivers, and in 'agricultural' areas, (3) good correspondences between stressors identified and restoration measures implemented. Morphological alterations were the most important highlighted stressors. River morphology enhancement, especially instream enhancements, were the most frequently implemented restoration measures. Some differences exist in specific restoration practices, as river continuity restoration were most frequently implemented in French projects, while large wood introduction or channel re-braiding were most frequently implemented in German projects, and (4) some quantitative and qualitative differences in monitoring practices and a significant lack of project monitoring, especially in Germany compared to France. These similarities and differences between Germany and France in restoration application and monitoring possibly result from a complex set of drivers that might be difficult to untangle (e.g., environmental, technical, political, cultural). [ABSTRACT FROM AUTHOR]

Water-borne pathogen contamination from untreated sewage effluent and runoff from farms is a serious threat to the use of river water for drinking and commercial purposes, such as downstream estuarine shellfish industries. In this study, the impact of climate change and land-use change on the presence of faecal indicator bacteria in freshwater was evaluated, through the use of a recently-developed catchment-scale pathogen model. The River Conwy in Wales has been used as a case-study, because of the large presence of livestock in the catchment and the importance of the shellfish harvesting activities in its estuary. The INCA-Pathogens catchment model has been calibrated through the use of a Monte-Carlo-based technique, based on faecal indicator bacteria measurements, and then driven by an ensemble of climate projections obtained from the HadRM3-PPE model (Future Flow Climate) plus four land-use scenarios (current land use, managed ecosystem, abandonment and agricultural intensification). The results show that climate change is not expected to have a very large impact on average river flow, although it might alter its seasonality. The abundance of faecal indicator bacteria is expected to decrease in response to climate change, especially during the summer months, due to reduced precipitation, causing reduced runoff, and increased temperature, which enhances the bacterial die-off processes. Land-use change can also have a potentially large impact on pathogens. The “managed ecosystems” scenario proposed in this study can cause a reduction of 15% in average water faecal indicator bacteria and up to 30% in the 90th percentile of water faecal indicator bacteria, mainly due to the conversion of pasture land into grassland and the expansion of forest land. This study provides an example of how to assess the impacts of human interventions on the landscape, and what may be the extent of their effects, for other catchments where the human use of the natural resources in the uplands can jeopardise the use of natural resources downstream. [ABSTRACT FROM AUTHOR]

Floods are a natural hazard evolving in space and time according to meteorological and river basin dynamics, so that a single flood event can affect different regions over the event duration. This physical mechanism introduces spatio-temporal relationships between flood records and losses at different locations over a given time window that should be taken into account for an effective assessment of the collective flood risk. However, since extreme floods are rare events, the limited number of historical records usually prevents a reliable frequency analysis. To overcome this limit, we move from the analysis of extreme events to the modeling of continuous stream flow records preserving spatio-temporal correlation structures of the entire process, and making a more efficient use of the information provided by continuous flow records. The approach is based on the dynamic copula framework, which allows for splitting the modeling of spatio-temporal properties by coupling suitable time series models accounting for temporal dynamics, and multivariate distributions describing spatial dependence. The model is applied to 490 stream flow sequences recorded across 10 of the largest river basins in central and eastern Europe (Danube, Rhine, Elbe, Oder, Waser, Meuse, Rhone, Seine, Loire, and Garonne). Using available proxy data to quantify local flood exposure and vulnerability, we show that the temporal dependence exerts a key role in reproducing interannual persistence, and thus magnitude and frequency of annual proxy flood losses aggregated at a basin-wide scale, while copulas allow the preservation of the spatial dependence of losses at weekly and annual time scales. [ABSTRACT FROM AUTHOR]

Our objectives were to offer insight into the characteristics of the physical environment in the River Danube in Serbia; and to show the relationship between selected environmental factors and the composition and abundance of macrophyte species. The macrophyte survey method followed the European Standard EN 14184, applying Kohler's fivelevel descriptive scale. Principal component analysis was carried out to examine the variation in aquatic vegetation and to analyze the effect of environmental variables on the aquatic vegetation, redundancy analysis was used. To build a simpler model with fewer explanatory variables, yet sufficiently explaining species variability, forward selection of environmental variables was done. Our results confirmed that physical environmental factors significantly influence the establishment and structure of macrophyte vegetation, with the level of hydrological connectivity to the main river channel being the most important, followed by the transparency of the water column, sediment texture and water-flow velocity. In order to inspect the individual relation between best-fitted plant species and each of selected environmental variables, Spearman's rank correlation coefficients were calculated. We have distinguished plant species with preferences to specific combinations of analyzed factors. Our results provide a background for future, more specific studies on the macrophyte/habitat relationship. [ABSTRACT FROM AUTHOR]

This article explores the alchemy whereby ritual and political worlds invisible to Europeans were rendered visible on European maps. It begins with a puzzle: representations of southwestern Africa's rivers on those maps bear little resemblance to physical reality as the cartographers would have understood it. Using GIS technology to georeference a series of maps and highlight the placement of rivers on them illustrates the convergence of cartographers’ representations and regional political cosmologies linking power to control over water. Travelers’ accounts and colonial archives illuminate how knowledge was produced and why African ideas about geography were inadvertently embedded in those maps well into the twentieth century. This method opens a window into otherwise-obscured African intellectual history and demonstrates that even something as apparently and unambiguously ‘European’ as modern mapping was the result of on-the-ground negotiations well into the colonial period. [ABSTRACT FROM AUTHOR]

This paper addresses the identification and evaluation of extreme flood events in the transitional area between western and central Europe in the period 1951-2013. Floods are evaluated in terms of three variants on an extremity index that combines discharge values with the spatial extent of flooding. The indices differ in the threshold of the considered maximum discharges; the flood extent is expressed by a length of affected river network. This study demonstrates that using the index with a higher flood discharge limit changes the floods' rankings significantly. It also highlights the high severity events. In general, we detected an increase in the proportion of warm half-year floods when using a higher discharge limit. Nevertheless, cold half-year floods still predominate in the lists because they generally affect large areas. This study demonstrates the increasing representation of warm half-year floods from the northwest to the southeast. [ABSTRACT FROM AUTHOR]

In Hungary, the high loess bank of the River Danube in Dunaszekcső has been moving with varying rate since 2007. On the high bank a geodetic monitoring network was established in September 2007. At the same time two borehole tiltmeters and later two ground water level sensors were also installed. The high-sensitive tiltmeters made it possible to study the relationships between the small tilts of the high bank and the ground water levels and the water level of the River Danube. Results of the multiple regression analysis between tilt components and water levels showed that the temporal variation of the regression coefficients is in close connection with the stability of the high bank. The investigations also showed that the movements are in very strong connection with the variation of the ground water level and less depend on the variation of the water level of the River Danube. The characteristic tilt processes, 3-4 weeks before large movements, and the slope stability changes inferred from the relationships between tilts and water level variations can be useful for early warning of landslides. [ABSTRACT FROM AUTHOR]

Pharmaceuticals as environmental contaminants have received a lot of interest over the past decade but, for several pharmaceuticals, relatively little is known about their occurrence in European surface waters. Benzodiazepines, a class of pharmaceuticals with anxiolytic properties, have received interest due to their behavioral modifying effect on exposed biota. In this study, our results show the presence of one or more benzodiazepine(s) in 86% of the analyzed surface water samples (n = 138) from 30 rivers, representing seven larger European catchments. Of the 13 benzodiazepines included in the study, we detected 9, which together showed median and mean concentrations (of the results above limit of quantification) of 5.4 and 9.6 ng L −1 , respectively. Four benzodiazepines (oxazepam, temazepam, clobazam, and bromazepam) were the most commonly detected. In particular, oxazepam had the highest frequency of detection (85%) and a maximum concentration of 61 ng L −1 . Temazepam and clobazam were found in 26% (maximum concentration of 39 ng L −1 ) and 14% (maximum concentration of 11 ng L −1 ) of the samples analyzed, respectively. Finally, bromazepam was found only in Germany and in 16 out of total 138 samples (12%), with a maximum concentration of 320 ng L −1 . This study clearly shows that benzodiazepines are common micro-contaminants of the largest European river systems at ng L −1 levels. Although these concentrations are more than a magnitude lower than those reported to have effective effects on exposed biota, environmental effects cannot be excluded considering the possibility of additive and sub-lethal effects. [ABSTRACT FROM AUTHOR]

Data on the seasonal and diurnal dynamics of downstream migration of smolts of the European river lamprey Lampetra fluviatilis are obtained. On the basis of published data and surveys in nature, it is shown that in the largest part of the area the downstream migration of smolts occurs mainly in spring, in the period of high water in rivers caused by snow melting. The smolts undertake downstream migration at night, under minimal illumination. It has been determined experimentally that the smolts are characterized by negative photopreferendum (>90% of smolts preferred illumination <0.4 lx). [ABSTRACT FROM AUTHOR]

A new atmospheric-river detection and tracking scheme based on the magnitude and direction of integrated water vapour transport is presented and applied separately over 13 regions located along the west coasts of Europe (including North Africa) and North America. Four distinct reanalyses are considered, two of which cover the entire twentieth-century: NOAA-CIRES Twentieth Century Reanalysis v2 (NOAA-20C) and ECMWF ERA-20C. Calculations are done separately for the OND and JFM-season and, for comparison with previous studies, for the ONDJFM-season as a whole. Comparing the AR-counts from NOAA-20C and ERA-20C with a running 31-year window looping through 1900-2010 reveals differences in the climatological mean and inter-annual variability which, at the start of the twentieth-century, are much more pronounced in western North America than in Europe. Correlating European AR-counts with the North Atlantic Oscillation (NAO) reveals a pattern reminiscent of the well-know precipitation dipole which is stable throughout the entire century. A similar analysis linking western North American AR-counts to the North Pacific index (NPI) is hampered by the aforementioned poor reanalysis agreement at the start of the century. During the second half of the twentieth-century, the strength of the NPI-link considerably varies with time in British Columbia and the Gulf of Alaska. Considering the period 1950-2010, AR-counts are then associated with other relevant large-scale circulation indices such as the East Atlantic, Scandinavian, Pacific-North American and West Pacific patterns (EA, SCAND, PNA and WP). Along the Atlantic coastline of the Iberian Peninsula and France, the EA-link is stronger than the NAO-link if the OND season is considered and the SCAND-link found in northern Europe is significant during both seasons. Along the west coast of North America, teleconnections are generally stronger during JFM in which case the NPI-link is significant in any of the five considered subregions, the PNA-link is significant in British Columbia and the Gulf of Alaska and the WP-link is so along the U.S. West Coast. During OND, these links are significant in the Gulf of Alaska only. If AR-counts are calculated upon persistent (instead of instantaneous) ARs, the link to the NAO weakens over the British Isles and western Iberia. For the experimental set-ups most closely mirroring those applied in Lavers et al. (J Geophys Res Atmos 117, 2012. doi:) and Ramos et al. (J Hydrometeorol 16(2):579-597, 2015. doi:), the NAO-links are completely or partly insignificant indicating that the inclusion of the persistence criterion notably alters the results. Visual support for the present study is provided by an exhaustive historical atmospheric river archive built at . [ABSTRACT FROM AUTHOR]

Numerous restoration campaigns focused on re-establishing species-rich floodplain meadows of Central Europe, whose species composition is essentially controlled by regular flooding. Climate change predictions expect strong alterations on the discharge regime of Europe’s large rivers with little-known consequences on floodplain meadow plants. In this study, we aim to determine the effects of flooding on seedlings of different ages of four typical flood meadow species. To this end, we flooded seedlings of two familial pairs of flood meadow species of wetter and dryer microhabitats for 2 weeks each, starting 2, 4, 6, and 8 weeks after seedling germination, respectively. We show that a 2-week-flooding treatment had a negative effect on performance of seedlings younger than 6 weeks. Summer floods with high floodwater temperatures may have especially detrimental effects on seedlings, which is corroborated by previous findings. As expected, the plants from wet floodplain meadow microhabitats coped better with the flooding treatment than those from dryer microhabitats. In conclusion, our results suggest that restoration measures may perform more successfully if seedlings of restored species are older than the critical age of about 6 weeks before a spring flooding begins. Seasonal flow patterns may influence vegetation dynamics of floodplain meadows and should, therefore, be taken into account when timing future restoration campaigns. [ABSTRACT FROM AUTHOR]

Cruise trips have been rising in popularity since the 1970sand are currently a trend in the tourism market. This is particularly true of river cruises, which record a constant growth in the number of ship calls. The general upward trend in the number of river cruise passengers and dockings is also present in Croatia. Prerequisites for the development of cruising on Croatian rivers include, in addition to other geographical features, also the length of navigable water ways, but a systematic approach to this issue is needed for further development. The authors investigate the level of development of infrastructure on Croatian rivers and analyse the passenger and ship traffic on them. Special attention is given to the importance of cruises for tourism on European rivers and worldwide. In accordance with the Croatian Tourism Development Strategy until 2020, the authors explore geographical and other conditions necessary for the development of river cruise tourism. The aim of the paper is to point to the importance of building infrastructure for accommodation of vessels sailing on Croatian rivers, and in particular to the need to improve tourism offer in river destinations. [ABSTRACT FROM AUTHOR]

In this study, we document sedimentary characteristics of overbank flood deposits associated with the epic A.D. 2011 flood along the Lower Mississippi River (southern USA) and directly compare the findings to sedimentation from a comparable flood event in 1973, with the general purpose of understanding how extreme floods contribute to floodplain depositional patterns and accretion rates of embanked fluvial systems. The thicknesses of the 2011 flood deposits averaged 138 mm along natural levee crests, 9 mm on meander scrolls, and 3 mm in backswamps. These thicknesses are considerably less than those documented for the 1973 flood, sampled at the same locations. We contend that less sedimentation in 2011 occurred because the flood was not supplied with much upstream sediment from the Missouri River. Further, the 2011 sediments are coarser than in 1973, indicating that the higher 2011 flood levels were associated with more energetic overbank flows that flushed fine-grained sediments downstream within the narrow embanked floodplain corridor. The largest recorded flood in North American history is only marginally preserved in the embanked floodplain stratigraphy of the alluvial valley of Earth's third largest fluvial system. [ABSTRACT FROM AUTHOR]

Non-perennial rivers and streams (NPRS) cover > 50% of the global river network. They are particularly predominant in Mediterranean Europe as a result of dry climate conditions, climate change and land use development. Historically, both scientists and policy makers underestimated the importance of NRPS for nature and humans alike, mainly because they have been considered as systems of low ecological and economic value. During the past decades, diminishing water resources have increased the spatial and temporal extent of artificial NPRS as well as their exposure to multiple stressors, which threatening their ecological integrity, biodiversity and ecosystem services. In this paper, we provide a comprehensive overview of the structural and functional characteristics of NPRS in the European Mediterranean, and discuss gaps and problems in their management, concerning their typology, ecological assessment, legislative and policy protection, and incorporation in River Basin Management Plans. Because NPRS comprise highly unstable ecosystems, with strong and often unpredictable temporal and spatial variability – at least as far as it is possible to assess – we outline the future research needs required to better understand, manage and conserve them as highly valuable and sensitive ecosystems. Efficient collaborative activities among multidisciplinary research groups aiming to create innovative knowledge, water managers and policy makers are urgently needed in order to establish an appropriate methodological and legislative background. The incorporation of NPRS in EU-Med River Basin Management Plans in combination with the application of ecological flows is a first step towards enhancing NPRS management and conservation in order to effectively safeguard these highly valuable albeit threatened ecosystems. [ABSTRACT FROM AUTHOR]

Complex mixtures of micropollutants, including pesticides, pharmaceuticals and industrial chemicals emitted by wastewater effluents to European rivers may compromise the quality of these water resources and may pose a risk to ecosystem health and abstraction of drinking water. In the present study, an integrated analytical and bioanalytical approach was applied to investigate the impact of untreated wastewater effluents from the city of Novi Sad, Serbia, into the River Danube. The study was based on three on-site large volume solid phase extracted water samples collected upstream and downstream of the untreated wastewater discharge. Chemical screening with liquid chromatography high resolution mass spectrometry (LC-HRMS) was applied together with a battery of in vitro cell-based bioassays covering important steps of the cellular toxicity pathway to evaluate effects on the activation of metabolism (arylhydrocarbon receptor AhR, peroxisome proliferator activated receptor gamma PPARγ), specific modes of action (estrogen receptor ERα, androgen receptor AR) and adaptive stress responses (oxidative stress, inflammation). Increased effects, significantly changed contamination patterns and higher chemical concentrations were observed downstream of the wastewater discharge. A mass balance approach showed that enhanced endocrine disruption was in good agreement with concentrations of detected hormones, while only a smaller fraction of the effects on xenobiotic metabolism (<1%) and adaptive stress responses (0–12%) could be explained by the detected chemicals. The chemical and effects patterns observed upstream of the discharge point were fairly re-established at about 7 km downstream, demonstrating the enormous dilution capacity of this large river. [ABSTRACT FROM AUTHOR]

Flood hazard is being analysed with ever-more complex models on national, continental and global scales. In this paper we investigate an alternative, simplified approach, which combines statistical and physical models in order to carry out flood mapping for Europe. Estimates of extreme river discharges made using a Bayesian Network-based model from a previous study are employed instead of rainfall-runoff models. Those data provide flood scenarios for simulation of water flow in European rivers with a catchment area above 100 km2. The simulations are performed using a one-dimensional steady-state hydraulic model and the results are post-processed using geographical information system (GIS) software in order to derive flood zones. This approach is validated by comparison with Joint Research Centre's (JRC) pan-European map and five local flood studies from different countries. Overall, both our and JRC's maps have similar performance in recreating flood zones of local maps. The simplified approach achieved similar level of accuracy, while substantially reducing the computational time. The paper also presents the summarized results from the flood hazard maps, including future projections. We find that relatively small changes in flood hazard are observed (increase of flood zones area by 2–4 %). However, when current flood protection standards are taken into account, there is a sharp increase in flood-prone area in the future (28–38 % for a 1000 year return period). This is because in many parts of Europe river discharge with the same return period is projected to increase in the future, thus making the protection standards insufficient. [ABSTRACT FROM AUTHOR]

Climate change is projected to increase the frequency of extreme events, such as flooding and droughts, which are anticipated to have negative effects on the biodiversity of primary producers and consequently the associated consumer communities. Here we assessed the effects of an extreme early summer flooding event in 2013 on ant colonies along an experimental gradient of plant species richness in a temperate grassland. We tested the effects of flood duration, plant species richness, plant cover, soil temperature, and soil porosity on ant occurrence and abundance. We found that the ant community was dominated by Lasius niger, whose presence and abundance after the flood was not significantly affected by any of the tested variables, including plant species richness. We found the same level of occupation by L. niger at the field site after the flood (surveyed in 2013) as before the flood (surveyed in 2006). Thus, there were no negative effects of the flood on the presence of L. niger in the plots. We can exclude recolonisation as a possible explanation of ant presence in the field site due to the short time period between the end of the flood and survey as well as to the absence of a spatial pattern in the occupancy data. Thus, the omnipresence of this dominant ant species 1 month after the flood indicates that the colonies were able to survive a 3-week summer flood. The observed ant species proved to be flood resistant despite experiencing such extreme climatic events very rarely. [ABSTRACT FROM AUTHOR]

This opinion paper introduces a special series of articles dedicated to freshwater benthic algae and their use in assessment and monitoring. This special series was inspired by talks presented at the 9th International Congress on the Use of Algae for Monitoring Rivers and Comparable Habitats (Trento, Italy, 2015), the latest of a series of meetings started in 1991. In this paper, we will first provide a brief overview of phytobenthos methods in Europe. Then, we will turn towards the ‘dark side’ of phytobenthos and describe four particular problems for phytobenthos assessment in the European Union: (1) over-reliance on a single group of algae (mostly diatoms) to the exclusion of other groups; (2) relatively low adoption of benthic algae for ecological assessments in lakes; (3) absence of measures of phytobenthos abundance; (4) approaches used to define boundaries between ecological classes. Following this, we evaluate the strengths and limitations of current phytobenthos assessment methods against 12 criteria for method evaluation addressing four areas: ecological rationale, performance, feasibility of implementation, and use in communication and management. Using these criteria, we identify and discuss three general challenges for those developing new methods for phytobenthos-based assessment: a weak ecological rationale and insufficient consideration of the role of phytobenthos as a diagnostic tool and for communicating ecosystem health beyond a narrow group of specialists. The papers in the special series allow a comparison with the situation and approaches in the USA, present new methods for the assessment of ecological status and acidification, provide tools for an improved management of headwaters and petrifying springs, discuss the utility of phytobenthos for lake assessments, and test the utility of functional measures (such as biofilm phosphorus uptake capacity, PUC). [ABSTRACT FROM AUTHOR]

• Monitoring of rivers, strategy of studies in the most industrialized region of Europe. • Water and invertebrate conditions significantly influenced by industrial catchment. • Salinity from mines as a driver for the ecological status of the rivers. • Industries as key decisive threat to good ecological river status of industrial region. • Existing strong need for monitoring studies in industrial areas. Many regions of the world are industrialised and urbanized like the Upper Silesian Coal Basin (USCB), which is located in one of the most industrialized areas of Europe. Due to the presence of coal and other mineral deposits and their excavation, this area is subject to extensive industrialization, including the functioning of mining and metallurgy industries. According to the Water Framework Directive, water released from mines contains a wide range of pollutants and hence poses a serious threat to the ecology of river systems, eventually resulting in their degradation. The aim of this study was to assess the ecological status of rivers located in the Vistula and Oder river basins, which are affected by the coal mining industry. In this study, macroinvertebrates were used as biological response on the water pollution, and were collected at 30 sampling sites in 12 rivers following the methodology of monitoring studies. The results revealed major differences in the parameters related to river salinity and nutrient loads in the studied rivers. Only the two rivers, Żylica and Liswarta, showed good ecological status, while bad ecological status was recorded for Bierawka, Rawa, Łęgoń, and Biała Przemsza rivers. A redundancy analysis of the results indicated the following: the quality class was positively related to the degree of conductivity; the density of macroinvertebrates was positively related to a higher content of N-NO 2 (Nitrite nitrogen) and EPT (The number of families from Ephemeropthera, Plecoptera and Trichoptera), ASPT (average score per taxon PL), and 1-GOLD (abundance of Gastropod, Oligochaeta, and Diptera) indices were positively related to a higher content of dissolved oxygen. The condition of water and benthic invertebrates was significantly influenced by the industrial catchment, which was apparent from the ecological status of the studied systems. The rivers in the most industrialized part of this area were found to be characterized by worse conditions. [ABSTRACT FROM AUTHOR]

Mercury (Hg), lead (Pb) and cadmium (Cd) are involved in mammalian brain damage. However, little is known about Pb and Cd brain levels in wildlife that reflect the geochemical background. The aims of the study include the estimation of Hg, Pb and Cd concentrations, and the determination of relationships between these elements in the brains of 94 mesocarnivores. Road-killed or hunted animals were obtained from north-western Poland near the Polish-German border. The investigation covered the native Eurasian otter Lutra lutra, badger Meles meles, pine marten Martes martes, beech marten M. foina, European polecat Mustela putorius, red fox Vulpes vulpes, and alien species: feral and ranch American mink Neovison vison, raccoon Procyon lotor and raccoon dog Nyctereutes procyonoides. Depending on the diet and environmental pollution, the carnivore brains accumulated toxic metals in varying amounts. The highest median Hg levels (in mg/kg dry weight, dw) were found in the piscivorous Eurasian otter and feral mink (2.44 and 3.96), Pb in the omnivorous raccoon (0.47), while Cd in minks (~0.06). We indicated that Pb-based ammunition is a significant source of the element in scavengers from hunting area, and we also found a significant correlation between Pb and Cd levels in the fox brain. Finally, this study is the first to suggest background levels for brain Pb and Cd in mesocarnivores (<0.50 and <0.04 mg/kg dw, respectively). [ABSTRACT FROM AUTHOR]

Skates (Rajidae) have been commercially exploited in Europe for hundreds of years with some species’ abundances declining dramatically during the twentieth century. In 2009 it became “prohibited for EU vessels to target, retain, tranship or land” certain species in some ICES areas, including the critically endangered common skate and the endangered white skate. To examine compliance with skate bans the official UK landings data for 2011–2014 were analysed. Surprisingly, it was found that after the ban prohibited species were still reported landed in UK ports, including 9.6 t of common skate during 2011–2014. The majority of reported landings of common and white skate were from northern UK waters and landed into northern UK ports. Although past landings could not be validated as being actual prohibited species, the landings’ patterns found reflect known abundance distributions that suggest actual landings were made, rather than sporadic occurrence across ports that would be evident if landings were solely due to systematic misidentification or data entry errors. Nevertheless, misreporting and data entry errors could not be discounted as factors contributing to the recorded landings of prohibited species. These findings raise questions about the efficacy of current systems to police skate landings to ensure prohibited species remain protected. By identifying UK ports with the highest apparent landings of prohibited species and those still landing species grouped as'skates and rays’, these results may aid authorities in allocating limited resources more effectively to reduce landings, misreporting and data errors of prohibited species, and increase species-specific landing compliance. [ABSTRACT FROM AUTHOR]

To help achieve effective longitudinal river connectivity, evaluation of the efficacy of fishway use by upstream-migrating fishes is needed. Larinier super active baffle (SAB) fishways are relatively cheap retrofit fish passes, suitable for low-head barriers, widespread in Europe and the most commonly fitted technical pass in Britain. Their suitability for non-salmonids, however, is poorly quantified. The efficacy of a 15% gradient SAB fishway and effects of flow regime and water temperature were tested for European river lamprey ( Lampetra fluviatilis ) using passive integrated transponder (PIT) and acoustic telemetry at a Crump weir on the River Derwent, Northeast England. In migration season 2013–14, over a wide range of flows, 90.1% of 350 tagged lamprey entered the fishway. One fish (0.3%) of those that entered the pass ascended successfully, even though measured water velocity was within laboratory-measured performance conditions for this species. Of 29 acoustic-tagged lamprey that visited the weir over the same period, four (13.8%) ascended it directly, during elevated flows. These data suggest that high turbulence and/or the physical characteristics of baffles may inhibit lamprey ascent of the pass. In migration season 2014–15, we tested the effect of adding studded modular plastic tiles adjacent to the fishway wall, employing PIT antennas separately interrogating the entrance and exit of each of the main fishway and tile routes. 85.8% (169) of 197 tagged lamprey entered the fishway, of which 72/169 (42.6%) entered the tile entrance. Passage efficiency of entrants was 7.1% (12/169), all of which used the tiled route. Reduced local flow velocity in combination with increased availability of resting habitat within the tiles may have facilitated increased passage. Although fishway passage efficiency increased after placement of the modular tiles, it remained half that measured for direct weir passage, both of which are inadequate for connectivity restoration. Quantitative tests of studded tiles placed on the sloping downstream weir face by comparison to control conditions may be more effective and are needed. This study demonstrates the importance of carrying out full-scale field tests to supplement possible solutions developed under laboratory conditions. [ABSTRACT FROM AUTHOR]