Large European Rivers Research Articles

Global versus local change effects on a large European river

Water temperature and discharge are fundamental to lotic ecosystem function, and both are strongly affected by climate. In large river catchments, however, climatic effects might be difficult to discern from background variability and other cumulative sources of anthropogenic change arising from local land and water management. Here, we use trend analysis and generalised linear modelling on the Loire, the longest river in France to test the hypotheses that i) long-term trends in discharge and river temperature have arisen from climate change and ii) climatic effects on water quality have not been overridden by local effects.Over 32years (1977–2008), discharge in the Middle Loire fell by about 100m3/s while water temperature increased by 1.2°C with greatest effects during the warm period (May–August). Although increasing air temperature explained 80% of variations in water temperature, basin-wide precipitation showed no long-term trend and accounted for only 18% of inter-annual fluctuations in flow. We suggest that trends in abstraction coupled with a potential increase in evapo-transpiration at the catchment scale could be responsible for the majority of the long-term discharge trend.Discharge and water temperature explained only 20% of long-term variations in major water quality variables (conductivity, dissolved oxygen, pH, suspended matter, biochemical oxygen demand, nitrate, phosphate and chlorophyll-a), with phosphate and chlorophyll declining contrary to expectations from global change probably as a consequence of improved wastewater treatment.These data partially support our first hypothesis in revealing how warming in the Loire has been consistent with recent atmospheric warming. However, local management has had larger effects on discharge and water quality in ways that could respectively exacerbate (abstraction) or ameliorate (reduced point-source pollution) warming effects. As one of the first case-studies of its kind, this multi-parametric study illustrates the potential for complex interactions between climate change and other environmental factors in large rivers.

The role of reference conditions in water quality assessment: application of a fuzzy logic-based Decision Support System (DSS) in the Danube and Elbe River Basins

The recent defi nition and submission of WFD-compliant River Basin Management Plans required large efforts of water managers and highlighted a number of data, knowledge and methodological gaps that need to be fulfi lled during the next management cycle. The complexity of the WFD implementation process calls for easy-touse, reliable and scientifi cally sound decision support tools that consider relevant aspects of the basin of concern. For this purpose, a Decision Support System (DSS) for risk-based assessment and management of river basins was developed within the EU MODELKEY project. The MODELKEY DSS allows assessing the chemical and ecological status of water bodies by applying both the One-Out All-Out principle, suggested by the WFD, and a novel Integrated Risk Assessment (IRA) methodology, developed within the project. In this paper, main results obtained by DSS application to two large European rivers, i.e. Elbe and Danube, are presented and discussed, based on a set of biological, chemical and physico-chemical indicators, which have been evaluated in relation to available reference conditions. The WFD ecological and chemical status assessment as well as analysis of intermediate results was strongly affected by the methods used to derive reference conditions, the applied indicators, and the methods used to aggregate indicators results. Minimally disturbed conditions (MDC) are the best choice as reference conditions, being characterized by generally high index values (good status) for all biological indices. Where MDC are not available, historical conditions could be a good substitute; they should be preferred to least disturbed sites (in particular when the river is generally impaired as the Danube River).

Evaluation of the mayfly Ephoron virgo for European sediment toxicity assessment

The mayfly Ephoron virgo plays a key role in the ecological recovery in large European rivers. The larvae spend their life in the sediment and are therefore exposed to contaminants in various ways. In this study, the use of E. virgo as a test species for whole sediment bioassays was evaluated. The sensitivity was compared with Hexagenia limbata (a North American mayfly recommended for standard sediment testing). Lead (Pb) was used as a model contaminant. Seven Pb concentrations (range, 100–3,200 μg g−1) were spiked to uncontaminated natural sediment. Prior to the bioassays, spiked sediments were equilibrated for 35 days to ensure the partitioning of Pb among overlying water, pore water and sediment. E. virgo and H. limbata were exposed to Pb-contaminated sediments for 21 days in the test jars containing 250 mg sediment (i.e. 4 cm deep; 250 ml test medium). The exposure was performed as a semi-static system of which overlying water was renewed twice per week. Pb concentrations in pore water and sediment were measured at the beginning and the end of the assays. Pb bioavailability in the sediment was assessed using the equilibrium partitioning model based on acid volatile sulphide (AVS) and simultaneously extracted metal (SEM). A clear dose–response relationship between E. virgo survival and Pb toxicity/bioavailability in the sediment was obtained, with the lowest observed effect concentration of 2,071 μg Pb g−1 treatment [(SEMPb–AVS)/fraction of organic carbon (OC) = 168.9 μmol g−1 OC]. The results also confirmed the SEM–AVS model as no Pb toxicity occurred at (SEMPb–AVS) ≤0 μmol g−1. Comparing the responses of the two mayfly species exposed to the same Pb-contaminated sediment, E. virgo showed a higher sensitivity. The difference in sensitivity to Pb of the two mayflies could be related to intrinsic species sensitivity. Some factors which might influence sensitivity, i.e. the developmental stage and homogeneity of the larval age at exposure, should also be considered. Comprehensive data for the risk assessment of European sediments may be obtained from sediment bioassays with indigenous species. In this study, a chronic sediment toxicity assay using larvae of E. virgo has been demonstrated. Considering the sensitivity and the need to incorporate more ecologically relevant data, it can be concluded that the 21-day whole sediment toxicity test with E. virgo is a good bioassay for testing sediment toxicity.

Ambient noise in large rivers (L)

This paper presents the results of hydroacoustic noise research in three large European rivers: the Danube, the Sava, and the Tisa. Noise in these rivers was observed during a period of ten years, which includes all annual variation in hydrological and meteorological conditions (flow rate, speed of flow, wind speed, etc.). Noise spectra are characterized by wide maximums at frequencies between 20 and 30 Hz, and relatively constant slope toward higher frequencies. Spectral level of noise changes in time in relatively wide limits. At low frequencies, below 100 Hz, the dynamics of noise level is correlated with the dynamics of water flow and speed. At higher frequencies, noise spectra are mostly influenced by human activities on river and on riverbanks. The influence of wind on noise in rivers is complex due to the annual variation of river surface. The influence of wind is less pronounced than in oceans, seas, and lakes.

Biogeochemical dynamics of perfluorinated alkyl acids and sulfonates in the River Seine (Paris, France) under contrasting hydrological conditions

The biogeochemical dynamics of 15 perfluorinated compounds (PFCs) were investigated in a heavily urbanised river (River Seine, Paris, France). The target compounds included C4-C10 sulfonates and C5-C14 acids; eleven PFCs were detected and ∑PFCs ranged between 31 and 91 ng L −1 (median: 47 ng L −1). The molecular pattern was dominated by the perfluoroalkyl sulfonates PFHxS and PFOS (>54% of ∑PFCs), which were the only PFCs quantified in both the dissolved and particulate phases. For these PFCs, the sorbed fraction positively correlated with suspended sediment levels. Total PFC levels negatively correlated with river flow rate, which varied between 150 and 640 m 3 s −1. This suggests the predominance of point sources (likely WWTP effluent discharge), but a contribution of non-point sources such as combined sewer overflow could not be excluded. The annual PFC mass flow was estimated at 500 kg, which is less than observed for other large European rivers.

POST‐DAMMING FLOW REGIME DEVELOPMENT IN A LARGE LOWLAND RIVER (VOLGA, RUSSIAN FEDERATION): IMPLICATIONS FOR FLOODPLAIN INUNDATION AND FISHERIES

ABSTRACTPeriodic flooding plays a key role in the ecology of floodplain rivers. Damming of such rivers can disturb flooding patterns and have a negative impact on commercial fish yield. The Volga River, the largest river in Europe, has a regulated flow regime after completion of a cascade of dams. Here, we study effects of damming on long‐term discharge variability and flood pulse characteristics. In addition, we evaluate the effects of the altered flood pulse on floodplain ecosystem functioning and commercial fish yields. Our results indicate that both flood pulse and fish populations of the Volga–Akhtuba floodplain have varied considerably over the past decades. After damming, annual maximum peak discharges have decreased, minimum discharges increased, but average discharges remained similar to pre‐damming conditions. Moreover, because of bed level incision of over 1.5 m, a higher discharge is needed to reach bankfull level and inundate the floodplains. Despite this significantly altered hydrological regime and subsequent morphological changes, current discharge management still provides significant spring flooding. However, commercial fish catches did decrease after damming, both in the main channel and in the floodplain lakes. All catches were dominated by species with a eurytopic flow preference, although catches from the main channel contained more rheophilic species, and floodplain catches contained more limnophilic and phytophilic species. The strong increase of opportunistic gibel carp (Carassius gibelio) around 1985 was apparent in the main channel and the floodplain lakes. Despite the hydrological changes, the decrease in overall catches, and the upsurge of gibel, we found a strong positive effect of flood magnitude in the previous year on commercial fish yield in the floodplain lakes. This suggests that under the current discharge management there still is an increased fish growth and/or survival during high floods and that functioning of the floodplain is at least partly intact. Copyright © 2011 John Wiley & Sons, Ltd.

Identifying robust large-scale flood risk mitigation strategies: A quasi-2D hydraulic model as a tool for the Po river

This paper focuses on the identification of large-scale flood risk mitigation strategies for the middle-lower reach of River Po, the longest Italian river and the largest in terms of streamflow. This study develops and tests the applicability of a quasi-2D hydraulic model to aid the identification of large-scale flood risk mitigation strategies relative to a 500-year flood event other than levee heightening, which is not technically viable nor economically conceivable for the case study. Different geometrical configurations of the embankment system are considered and modelled in the study: no overtopping; overtopping and levee breaching; overtopping without levee breaching. The quasi-2D model resulted in being a very useful tool for (1) addressing the problem of flood risk mitigation from a global - perspective (i.e., entire middle-lower reach of River Po), (2) identifying critical reaches, inundation areas and corresponding overflow volumes, and (3) generating reliable boundary conditions for smaller scale studies aimed at further analyzing the hypothesized flood mitigation strategies using more complex modelling tools (e.g., fully 2D approaches). These are crucial tasks for institutions and public bodies in charge of formulating robust flood risk management strategies for large European rivers, in the light of the recent Directive 2007/60/EC on the assessment and management of flood risks ( European Parliament, 2007).

Suspended sediment dynamics in a large regulated river over a 10-year period (the lower Ebro, NE Iberian Peninsula)

This paper presents a comprehensive assessment of the suspended sediment load for the period (1998–2008) in the lower river Ebro (NE Iberian Peninsula), one of the most regulated large rivers in Europe. Sediment load estimates are based on continuous discharge and turbidity records, calibrated with direct suspended sediment samples covering a wide range of river's hydraulic conditions. The temporal variability of the sediment load and the role of the effective discharge at different temporal scales are specifically examined. At the log-term, the study period can be considered as dry. Mean annual load is estimated at around 0.092 × 10 6 t, a value that represents less than the 1% of what was transported at the beginning of the twentieth century in the absence of dams and under different land uses. In general, sediment concentrations observed between 1998 and 2008 are low (mean was 9 mg l − 1 and maximum was 240 mg l − 1 ). Specific sediment yield was in the order of 1 t km 2 y − 1 , also much lower than values reported in other western European rivers of the same scale and impact. At the annual scale, large floods were responsible for most of the transported suspended sediment (up to 80%). Nevertheless, when the effective discharge is calculated for the whole study period, floods of moderate magnitude and high frequency are responsible for the largest amount of sediment transport. The temporal scale used to calculate the effective discharge thus determines the final results. Load estimates derived from continuous suspended sediment and discharge data and from the flow duration method yielded similar values. This suggests that the latter method is also appropriate when sediment samples cover a large proportion of the observed discharges and statistical significant relations can be obtained and applied to long periods of record. This study provides further insights into the sedimentary status of one of the largest rivers in Europe. Results corroborate previous studies highlighting sediment deficit downstream from large dams. This type of information constitutes a key element to inform and improve current management and restoration actions.

The River Volga headwaters: Inventory, biodiversity and conservation

River headwaters in the East European lowlands, such as the Upper Volga River, still contain large reaches exhibiting natural conditions and unaltered type-specific fauna. This article focuses on macroinvertebrate assemblages of this intact lowland river system. The presented inventory on aquatic biodiversity and habitat-specific invertebrate assemblages provides a basis to test general ecological theories in large European rivers and to define future management. A total of 204 taxa in seven phyla were identified in the headwaters of the Volga River, i.e. along 446 river kilometres, and its main tributaries. Arthropods were the most diverse group, followed by Annelida and Mollusca. Many species (up to 41 %) of the lake littoral were also common in the slow flowing (lentic) section of the river. Diversity, abundance and biomass increased along the river course. The number of reference taxa, defined in a previous paper, also increased downstream from 15 to 21. From the 30 tributaries 120 taxa were identified; 19 of which were from 24 reference taxa. Analysis of beta-diversity showed that 50 % of species were common to the main river and its tributaries. The Upper Volga lakes can be characterised as Chironomus plumosus lakes. The natural free flowing section and its tributaries comprise a diverse epipotamal fauna. Downstream from the Upper Volga Lakes, the functional feeding groups followed the predictions of the River Continuum Concept: in the upper reaches the community is composed of filter feeders, followed by grazers, predators, detritivores and shredders while further downstream detritivores became slightly dominant.

Testing the coherence of several macroinvertebrate indices and environmental factors in a large lowland river system (Volga River, Russia)

Abstract In contrast to most large rivers in Europe, the biggest European river Volga including its tributaries has still remained uncontaminated in its headwaters. Therefore the upper Volga River system represents an appropriate system for investigation of relations of bioassessment indices with natural environmental factors. Moreover, it allows the definition of reference conditions for medium-size and large lowland rivers in Europe. The aim of this study was to analyse relations between Saprobic Index (SI), SPEAR indices, and other macroinvertebrate community indices and basic environmental factors in the upper Volga River system. Besides, preliminary ecological status classification (according to the EU Water Framework Directive) was proposed for SI and SPEAR pesticides indices for the system investigated. The analysed data set contained information on macroinvertebrates, basic habitat characteristics and water physico-chemical parameters from 53 sample sites. The results showed that SI and SPEAR indices were independent of channel width and related river longitudinal factors. Furthermore, the results indicated the index SPEAR pesticides to be potentially applicable across different types of watercourses as well as across different biogeographical regions in Europe showing similar boundaries of ecological status classes (at least between High, Good, and Moderate). A Multi-Habitat-Sampling method was recommended for SPEAR pesticides . Saprobic reference conditions of the lowland rivers were found to be beta-mesosaprobic. The relatively high boundary between High and Good classes resulted from naturally high organic matter concentrations. Due to indicating common pollution sources (i.e. organic, agricultural and industrial), the herein suggested methodologies have a potential to be applied in other large river systems in Europe. The reference condition characteristics described for the headwaters of the Volga River system can be used as a reference for medium-sized and large rivers in the regions where establishment of reference sites of these types is impossible (e.g., many regions in Europe).

Impact of macroinvertebrate diet on growth and fatty acid profiles of restocked 0+ Atlantic salmon (Salmo salar) parr from a large European river (the Allier)

The influence of macroinvertebrate diet on growth and fatty acid profiles of Atlantic salmon ( Salmo salar ) parr released at the fry stage in three different riffles was studied in a large temperate river (Allier, France). Comparisons were made between sites and between restocked parr and hatchery-reared counterparts fed with a traditional fish diet. Significant differences were observed along the longitudinal gradient of the river and between restocked and hatchery-reared parr. Growth performance and nutritional status were higher in the hatchery and in downstream riffles and low in the most upstream site. These differences appeared to be related to different types of diet and consequently to variations in polar and neutral lipid intakes. The most favorable site for optimum growth appeared to be the intermediary riffle, with values close to those achieved in the hatchery. Simuliids and baetids, preferentially consumed in downstream sites, constitute an interesting type of food, showing quite different fatty acid composition from vegetable oils. This could be of interest for composing a new diet formula for young salmon intended for river restocking, imitating these macroinvertebrate fatty acid profiles.

LISFLOOD: a GIS‐based distributed model for river basin scale water balance and flood simulation

In this paper we describe the spatially distributed LISFLOOD model, which is a hydrological model specifically developed for the simulation of hydrological processes in large European river basins. The model was designed to make the best possible use of existing data sets on soils, land cover, topography and meteorology. We give a detailed description of the simulation of hydrological processes in LISFLOOD, and discuss how the model is parameterized. We also describe how the model was implemented technically using a combination of the PCRaster GIS system and the Python programming language, and discuss the management of in‐ and output data. Finally, we review some recent applications of LISFLOOD, and we present a case study for the Elbe river.

Effect of habitat-related resources on fatty acid composition and body weight of the invasive Dikerogammarus villosus in an artificial reservoir

Successful invasions are attributed to a combination of adaptations to biotic and abiotic conditions and many studies have highlighted the role of biological traits of invaders in their success. Among the most useful traits for successful establishment in a new ecosystem are the size of the invader and its diet and feeding habits. During the last twenty years, Dikerogammarus villosus has been one of the most successful invaders of large European rivers and lakes. However, regarding feeding habits, results were confusing and sometimes contradictory. In this study, we attempt to define the feeding strategy of D. villosus using their FA content according to sex and the seasonal and the spatial variation in its feeding habit. Our results indicated that D. villosus is rather unspecialized with plasticity in its feeding behaviour, switching between different functional feeding groups depending on seasons, habitats and available resources. The selection of high quality resources may hence provide a strong advantage during the invasion process by optimizing the growth and the reproduction of the invader.

Effects of suspended matter quality and virus abundance on microbial parameters: experimental evidence from a large European river

In riverine water, both suspended particulate material and viruses are prominent ecological factors. The existence of various particle types and differences in viral abundance impose variability in microenvironments. Particulates and their microbial surrounding may interact in several ways, this interaction being strongly dependent on particle quality and the abundance of organisms involved. In laboratory experiments, we used different suspended matter types (fresh and aged mineral sediment and leaf litter, river snow) that typically occur in riverine environments as model particles. We investigated the effects of particle quality and different ambient viral abundances (×1, ×2 enrichments, and inactivated viruses) on several microbial parameters (changes in bacterial and viral abundances, bacterial production, specific bacterial production) of both the free-living and particle-attached fractions using water from a floodplain system of the Danube River (Austria). Both seston quality and variable viral abundances in the bulk water influenced some microbial parameters. The average abundance of bacteria and viruses was significantly higher on organic than on inorganic particles and on aged particles (for both sediment and leaf litter). Changes in bacterial abundance during the course of the experiments were also influenced by particle quality, with, for example, aged sediment favoring increasing abundances. Virus:bacterium ratios (VBR) were significantly higher on organic than on inorganic particles, but significantly lower on suspended particles than in the plank-tonic fraction. Typically, bacterial secondary production (overall and cell-specific) was higher on particles than in bulk water. Bacterial productivity in the ambient water was negatively affected by the abundance of planktonic viruses but positively affected by that of attached viruses. These findings from experimental systems may foster in situ studies of particle-rich environments.

Feeding, growth and nutritional status of restocked salmon parr along the longitudinal gradient of a large European river: the Allier

Abstract – The feeding, growth and nutritional status of salmon parr (0+) released at fry stage in different riffles were studied in a large temperate river (Allier, France) throughout the active feeding period. Significant differences were observed along the upstream–downstream gradient. Parr growth performance and energy storage were higher in downstream riffles and low in the most upstream one. These longitudinal growth variations are discussed in the context of diet and food availability differences, habitat variables and intra‐ and inter‐species competition. The most favourable site for optimum growth and nutritional status appeared to be the intermediary riffle located in the grayling zone.

Sources and composition of organic matter for bacterial growth in a large European river floodplain system (Danube, Austria)

Dissolved and particulate organic matter (DOM and POM) distribution, lignin phenol signatures, bulk elemental compositions, fluorescence indices and microbial plankton (algae, bacteria, viruses) in a temperate river floodplain system were monitored from January to November 2003. We aimed to elucidate the sources and compositions of allochthonous and autochthonous organic matter (OM) in the main channel and a representative backwater in relation to the hydrological regime. Additionally, bacterial secondary production was measured to evaluate the impact of organic carbon source on heterotrophic prokaryotic productivity. OM properties in the backwater tended to diverge from those in the main channel during phases without surface water connectivity; this was likely enhanced due to the exceptionally low river discharge in 2003. The terrestrial OM in this river floodplain system was largely derived from angiosperm leaves and grasses, as indicated by the lignin phenol composition. The lignin signatures exhibited significant seasonal changes, comparable to the seasonality of plankton-derived material. Microbially-derived material contributed significantly to POM and DOM, especially during periods of low discharge. High rates of bacterial secondary production (up to 135 μg C L −1 d −1) followed algal blooms and suggested that autochthonous OM significantly supported heterotrophic microbial productivity.

Comparison of the components of the planktonic food web in three large rivers (Rhine, Moselle and Saar)

AbstractThe dynamics of phyto‐, bacterio‐, proto‐ and metazooplankton were investigated for a period of 22 months fortnightly from March 1999 until December 2000 in the rivers Moselle, Saar and Rhine. Plankton abundances reached the lowest values in the Rhine and the highest in the Saar. Protozoa and not the much more studied metazoa clearly dominate the zooplankton not only by number but also by biomass by about 90%. We show that the plankton biomass in each of the rivers is the result of the interplay of the grazing by benthic predators and of the human induced factors such as river morphology, water residence time and nutrient load. Furthermore, we compare our study with the planktonic food web of three other large European rivers. The comparison between all studies revealed a general rise of the absolute mean biomass of all heterotrophic planktonic food web components (bacteria, protozoa, metazoa) parallel to an increase of the algal biomass of the river. For the rivers Rhine, Moselle and Saar, the average biomass of all investigated plankton groups was very low compared to the values obtained in the rivers Meuse, Loire and Elbe. The relative importance of organisms of the microbial food web increased with a decrease of the algal biomass or organic carbon content, respectively, in each of the rivers. We postulate that with a sinking nutrient level in the Rhine, the microbial food web components will become even more important within the plankton than they already are. Copyright © 2008 John Wiley & Sons, Ltd.

Extreme water levels of the Vistula River and Gdansk Harbour

Using Canonical Correlation Analysis (CCA), Rozynski et al. (2006) have demonstrated that there is a weak correlation between the water levels of Vistula River and Gdansk Harbour. Herein the CCA analysis serves as a first step for a univariate bootstrap resampling technique, applied to investigate coincident extreme water levels of Vistula River and Gdansk Harbour. The CCA-derived assumption of statistical independence is argued as being a suitable working approximation for (outline) engineering design. This allows the goodness-of-fit of different statistical models to be assessed in a quantitative manner with a bootstrap method. This also provides a convenient means of defining extreme levels together with their confidence intervals. The analysis with two statistical methods provides insight into the character of joint coastal extremes in an estuary of a large north European river. The rationale and methodology are at least partly applicable to similar estuaries of northern Europe.

Occurrence and distribution of selected antibiotics in a small Mediterranean stream (Arc River, Southern France)

Summary The occurrence and distribution of nine selected antibiotics were investigated in a small Mediterranean stream (Arc River, Southern France) during the winter and the spring season. Carbamazepine and clarithromycin were the most frequently detected compounds in water. Clarithromycin was determined at high μg/L levels in river water during the winter season due to the lack of dilution by background water while clarithromycin and azithromycin were ubiquitous in sediment. These contamination levels were at one order of magnitude higher than those reported in large European rivers. It could be shown that clarithromycin can be regarded as a priority antibiotic to be monitored in river waters mainly because this chemical showed high persistence in water and underwent slow dissipation processes in sediment.

Paramecium Species of the Upper and Lower Volga River Basin, Russia

The Volga, which is the largest river in Europe (3690 km long), flows from the north (Tver' region) to the south (Caspian Sea), and its extensive basin (1380 km2) includes very different biotopes. Thus, analysis ofthe occurrence of Paramecium species along this large river basin may significantly enhance our understanding of species distribution according to temperature regime, food richness and other possible factors. The present paper concerns the occurrence of species of the P. aurelia complex in the sampling areas of the Upper Volga River, and a comparison with the occurrence of species of the P. aurelia complex in the Lower Volga region. In the Upper Volga basin, P. biaurelia was the most abundant among species of the complex recorded (among P. triaurelia, P. decaurelia, P. dodecaurelia), in the Lower Volga region eight species of the complex were recorded (P. primaurelia, P. biaurelia, P. triaurelia, P. pentaurelia, P. sexaurelia, P. septaurelia, P. novaurelia, P. decaurelia).