Danube Basin Research Articles

Sedimentänderung wurde ein signifikantes Wasserbewirtschaftungsthema im Donaueinzugsgebiet – basierend auf dem EU-Projekt DanubeSediment

ZusammenfassungIn vielen Flusseinzugsgebieten ist eine zunehmende Diskrepanz zwischen Überschuss und Defizit an Sedimenten zu beobachten. Dies führt zu einem Anstieg des Hochwasserrisikos, einer Einschränkung der Schifffahrtsmöglichkeiten und der Stromerzeugung aus Wasserkraft und wirkt sich negativ auf die Ökologie aus. Eine Hauptaufgabe des Wasserbaus ist daher die Verbesserung des Sedimentmanagements und der Flussmorphologie. Um bestehende Wissenslücken zu schließen, wurden entlang der gesamten Donau quantitative Sedimentdaten erhoben und analysiert. Es wurde eine Sedimentbilanz erstellt, die die Probleme aufzeigt, die sich aus der Sedimentdiskontinuität ergeben. Das Einzugsgebiet der Donau stellt insbesondere aufgrund der Unausgewogenheit des Sedimentregimes ein stark gestörtes System dar. Der Eintrag von Schwebstoffen in das Schwarze Meer wurde beispielsweise von rund 40 bis 60 Mio. Tonnen pro Jahr auf etwa 15 bis 20 Mio. Tonnen pro Jahr verringert, was zu einer verstärkten Küstenerosion führte. Darüber hinaus wurden in den letzten 200 Jahren lange Abschnitte der Donau eingeengt, reguliert und von den Überflutungsflächen abgetrennt sowie morphologisch degradiert. Dies hat zu erhöhten Sohlschubspannungen und in der Folge zu einer erhöhten Sedimenttransportkapazität geführt. Als Folge der longitudinalen und lateralen Unterbrechungen des Sedimentkontinuums und der zusätzlichen Auswirkungen der Regulierung sind die verbleibenden frei-fließenden Abschnitte der Sohlerosion ausgesetzt. Dies führt im Allgemeinen zu einem Verlust von Strukturen im Fluss, mit einem Verschwinden von Kiesbänken an der oberen Donau und Veränderungen von Sandbänken an der unteren Donau. In den Stauräumen herrscht das Gegenteil, nämlich Sedimentation, die teilweise auch Hochwasserschutzprobleme mit sich bringt. Da die Donau ein in Summe gestörtes Sedimentregime aufweist wurde im dritten Donau-Flussgebietsbewirtschaftungsplan die Änderung der Sedimentverhältnisse als signifikantes Wasserbewirtschaftungsthema verankert. Mögliche Antworten auf diese Probleme werden durch einen Maßnahmenkatalog gegeben.

Initial results of the colorimetric indices of the oldest exposed pedocomplex (Titel loess plateau, Serbia)

n this study we present an in-depth description of the colorimetric values for the lowest section of the Dukatar Loess Palaeosol Sequence (LPS) pedocomplex S5. Formed during the Marine Isotope Stage (MIS) 13-15, it represents the oldest pedocomplex exposed at the base of the Titel loess plateau (TLP), near the confluence of the Tisa and Danube rivers in Vojvodina (northern Serbia). The results of low-field magnetic susceptibility measurements (χlf) were compared to colour properties (obtained by conventional methods as well as instrumental measuring) and quantified Soil Development Indices (SDI). Of these measurements we found that the Redness Index (RI1) yielded the most useful results, as this index appears most sensitive to lithological changes and soil development intensity. It was also observed that a high level of correlation existed between χlf, and a* chromaticity. The initial results of this study highlight the utility of colorimetric methods as an interdisciplinary tool when evaluating the presence of ferromagnetics, and the application of rock magnetism to the Middle and Upper Pleistocene LPS of the Middle Danube Basin. The presented approach can be used to observe the evolution of climatic and ecological conditions in the given study area, and for establishing correlations between sites extending over the Eurasian LPS provinces.

Study of the Polymorphism of ISSR Markers in Spined Loaches of the Genus Cobitis (Cobitidae) in Connection with Problems of Differentiation of the Species Involved in the Formation of Polyploid Forms of Hybrid Origin and Determination of Their Taxonomic Status

We have analyzed the polymorphism of ISSR fragments of DNA by polymerase chain reaction in spined loaches for the first time. The analysis has made it possible to successfully differentiate the genomes, which were presumably involved in the formation of polyploid forms of hybrid origin: Cobitis taenia; spined loaches from the Danube River basin, which are diagnosed as C. elongatoides; C. tanaitica from the Don River basin and spined loaches from Lake Sinoe, which are also assigned to the species C. tanaitica by a number of authors. The following conclusions have been made based on comparative morphological studies of previously undifferentiated forms: (1) spined loaches from Central Europe with karyotype 2n = 50, NF = 96 correspond to the diagnosis of the species C. elongatoides; this species also differs from a number of closely related species and polyploid forms in the origin of the dorsal fin in front of the base of the pelvic fins, as well as in the presence of a spot in the lower half of the caudal fin base; (2) spined loaches from Lake Sinoe and other populations of Central Europe with karyotype 2n = 50, NF = 86 are nonconspecific to C. tanaitica and should apparently be ranked as an independent species, C. megaspila.

The Geopolitical and Geostrategic Importance of the Danube in the Context of European Security

Abstract The work aims to make a contribution in the vast field of the concept of geopolitical system, applied to the geopolitics of the Danube. The location of the Danube basin within the European Union has made it possible to redefine the regional cooperation of the riparian states on the coordinates of Community policies and instruments. EU strategists for the Danube region highlight the strategic and economic stakes of the Danube, the emphasis being placed on achieving more efficient connections for transport, trade and energy..

Occurrence of plant pathogenic Pseudomonas syringae in the Danube River Basin: abundance and diversity assessment

Plant pathogenic strains of Pseudomonas syringae (Psy) spp. have been detected in nonagricultural habitats, including those associated with the water cycle. Their presence in aquatic systems allows dissemination over long distances, especially with irrigation practices. In May 2021, we sampled 15 sites along the Danube River Basin in Serbia to gain insight into P. syringae abundance and diversity. We identified 79 Psy strains using Psy-specific primers, and a partial sequence of the citrate synthase (cts) house-keeping gene has served for phylogenetic diversity assessments. Phenotypic diversity determination included characterizing features linked with survival and pathogenic lifestyle. The ice nucleation activity, pectinolytic activity, swimming and swarming assays, and hypersensitive reaction on plants were tested. Psy was detected at ten of 15 sites examined at abundance ranging from 1.0 × 102 to 1.2 × 104 CFU/L. We discovered the presence of four phylogroups, with phylogroup 2 being the most abundant, followed by phylogroups 7, 9, and 13. The hypersensitive reaction was induced by 68.63% of the isolates from the collection. A partial sequence comparison of the cts gene showed 100% similarity between isolates from cherry plants epidemics in Serbia caused by Psy and isolates from the Danube River. Our results suggest that the Danube River, extensively used for irrigation of agricultural fields, harbors diverse strains of Psy, which possess various features that could lead to potential disease outbreaks on crops. This study represents the first in-depth analysis of Psy abundance and diversity in the Danube River Basin. It sets the ground for future pre-epidemic studies and seasonal monitoring of Psy population dynamics.

Study of the Polymorphism of ISSR Markers in Spined Loaches of the Genus Cobitis (Cobitidae) in Connection with Problems of Differentiation of the Species Involved in the Formation of Polyploid Forms of Hybrid Origin and Determination of Their Taxonomic Status

We have analyzed the polymorphism of ISSR fragments of DNA by polymerase chain reaction in spined loaches for the first time. The analysis has made it possible to successfully differentiate the genomes, which were presumably involved in the formation of polyploid forms of hybrid origin: Cobitis taenia; spined loaches from the Danube River basin, which are diagnosed as C. elongatoides; C. tanaitica from the Don River basin and spined loaches from Lake Sinoe, which are also assigned to the species C. tanaitica by a number of authors. The following conclusions have been made based on comparative morphological studies of previously undifferentiated forms: (1) spined loaches from Central Europe with karyotype 2n = 50, NF = 96 correspond to the diagnosis of the species C. elongatoides; this species also differs from a number of closely related species and polyploid forms in the origin of the dorsal fin in front of the base of the pelvic fins, as well as in the presence of a spot in the lower half of the caudal fin base; (2) spined loaches from Lake Sinoe and other populations of Central Europe with karyotype 2n = 50, NF = 86 are nonconspecific to C. tanaitica and should apparently be ranked as an independent species, C. megaspila

Conservation Status and Effectiveness of the National and International Policies for the Protection and Conservation of Sturgeons in the Danube River and Black Sea Basin

Rivers and their watersheds have been subject to various changes, including biodiversity, caused by anthropogenic activities. The Danube River and Black Sea basin overlap the geographic range of six species of anadromous fish belonging to the family Acipenseridae. Nowadays, they are endangered or at risk of extinction in the wild due to fragmentation and destruction of natural habitats, blocking their migration to spawning grounds, water pollution, and poaching. This paper presents a review of the historical and current distribution and evolution of the sturgeon populations of sturgeon species in the Danube River basin. Conservation status and measures for species protection, conservation, and restoration at the national, regional, and global levels are presented.

Copulas modelling of maize yield losses – drought compound events using the multiple remote sensing indices over the Danube River Basin

Copulas modelling of maize yield losses – drought compound events using the multiple remote sensing indices over the Danube River Basin

Identification of Areas with Significant Flood Risks in Counties along the Danube River in Serbia and Their Risk Assessment

For countries along the Danube River, their sustainable economic and social development needs the optimum water utilization of both the Danube and its tributaries. In the context of climate change, the risks of floods and natural hazards must be managed, because these risks have caused noticeable damages to the environment, people and their property. The countries along the Danube River have a long tradition of international cooperation in this field. Primarily based on the experience of European countries and literature on flood risk management, this research aimed to acquire up-to-date knowledge, emphasize the importance of integrated and high-quality information, and use the information as flood risk management technology and tool. Some areas in the Danube basin in Serbia have been identified with significant flood risks. Taking these areas as an example, this paper presented flood risks caused by the Danube and a map predicting those risks. In addition, this paper studied relevant information on flood risk management and flood hazards, such as possible scopes and impacts (damages) of floods, as well as their frequency and mechanism in the case study of Serbia. In this context, knowledge and understanding of these natural hazards, as well as geographic information and technology can be used for further planning and control, thus minimizing flood risks.

The Copula Application for Analysis of the Flood Threat at the River Confluences in the Danube River Basin in Slovakia

In hydrological practice, individual elements of the hydrological cycle are most often estimated and evaluated separately. Uncertainty in the size estimation of extrema discharges and their return period can affect the statistical assessment of the significance of floods. One example is the simultaneous occurrence and joining of extremes at the confluence of rivers. The paper dealt with the statistical evaluation of the occurrence of two independent variables and their joint probabilities of occurrence. Bivariate joint analysis is a statistical approach for the assessment of flood threats at the confluence of rivers. In our study, the annual maximum discharges monitored on four selected Slovak rivers and their tributaries represent the analyzed variables. The Archimedean class of copula functions was used as a set of mathematical tools for the determination and evaluation of the joint probability of annual maximal discharges at river confluences. The results of such analysis can contribute to a more reliable assessment of flood threats, especially in cases where extreme discharges occur simultaneously, increasing the risk of devastating effects. Finally, the designed discharges of the different return periods calculated by using the univariate approach and the bivariate approach for the gauging station below the confluence of the rivers was evaluated and compared.

ASSESSMENT OF RIVER SEDIMENT QUALITY ACCORDING TO THE EU WATER FRAMEWORK DIRECTIVE IN LARGE RIVER FLUVIAL CONDITIONS. A CASE STUDY IN THE LOWER DANUBE RIVER BASIN

Increase of pollution of surface water and water sediments with hazardous substances (HSs) in the Danube River Basin requires implementation of systematic monitoring and evaluation of the sediment quality. The present study is focused on the ’South Danube’ Test Area (SDTA) that covers parts of the Lower Danube Basin in Romania, Serbia and Bulgaria. The SD area represents an extended region where Danube reaches its largest widths and depths and where pollution (industrial, mining, agricultural, waste etc.) from tributaries and land is supposed to accumulate in the sediments. Sampling of river bottom sediment (BS), suspended sediment (SS) and overbank (floodplain) sediment at two layers (0-5 cm in the top layer (FS TS) and 40-50 cm in the bottom layer (FS BS)), was carried out at 11 locations in order to analyze the concentration and distribution of 8 metal(oid)s (Cu, Pb, Zn, Cd, Hg, Ni, Cr, As), 6 polycyclic aromatic hydrocarbons (PAHs) and 6 pesticides as hazardous substances. The 2013/39/EU Directive and EU Water Framework Directive standards were used to sediment quality assessment. As a whole, the concentrations of heavy metals in the sediments are comparatively low and are around the normal values for soils. On the other hand, some sampling sites and sediment types have high or very high metal concentrations which exceed intervention levels. Our study well recognizes mining pollution sources in the Danube tributaries Borska Reka, Timok, Ogosta, Malak Iskar and Iskar from past and/or recent mining activity. This pollution is limited to the Danube tributaries and around their confluences into the Danube River. The concentration of heavy metals is strongly diluted in the Danube River and drops around normal values. The studied sediments reveal low concentrations of PAHs. Only fluoranthene content is higher in most of the sediment types and sampling sites on the Danube River, but exceeds the interventional level only at Pristol and at Hârșova. Our results show that the sediments in the Danube River are more polluted with PAHs than its tributaries. The identified organic compounds are assumed to be generated during incomplete or low temperature combustion processes or during road transportation and/or the navigation on the Danube River.

Characteristics and Driving Mechanism of Water Resources Trend Change in Hanjiang River Basin.

Studying the historical and future trends of water resources in a basin and explaining the causes of water resource changes is very important, which is key to the management of water resources in a basin. The Hanjiang River Basin is an important water supply source for southwestern Fujian and eastern Guangdong, but it has an uneven spatial and temporal distribution of water resources and an outstanding conflict between supply and demand. In this study, the SWAT model was used to simulate the conditions of the Hanjiang River Basin in the last 50 years, using long time series climate data to study the characteristics and driving mechanism of water resources trend change. The results show that the water resources in the basin have not increased significantly in the last 50 years, but evapotranspiration has increased significantly. The forecast results for water resources in the future are reduced. The water resource changes in the basin have been unevenly distributed in the last 50 years. Climate change has been the main factor in total water resource change in the basin, while the difference in water resource change trends within the basin is caused by land use. The key reason for the decrease in water resources in the Hanjiang River Basin is the significant increase in evapotranspiration due to the significant increase in temperature. If this situation continues, the available water resources in the basin will continue to decline. In fact, many basins around the world are currently likely to have such problems, such as the 2022 summer drought in the Danube River Basin in Europe and the Yangtze River Basin in China, so this article is informative and representative of future water resources management in the basin.

Battery of In Vitro Bioassays: A Case Study for the Cost-Effective and Effect-Based Evaluation of Wastewater Effluent Quality

Wastewater treatment plants (WWTPs) represent an important input of contaminants in the environment. Therefore, it is critical to continuously monitor the performance of WWTPs to take appropriate action and avoid an influx of contaminants in the environment. In this study, a battery of seven in vitro bioassays covering a selected spectrum of toxicity effects is proposed for quality control of wastewater effluents. The bioassays address mixture toxicity, which is the combined adverse effect of multiple contaminants and can act as an early warning system. The proposed battery was applied to samples from 11 WWTPs of representative technology from the Danube River Basin (DRB). The order of toxic effects in terms of extent of exceedance of effect-based trigger values (EBTs) was PAH (PAH activity) > PXR (xenobiotic metabolism) > ERα (estrogenic activity) > PPARγ > Nrf2 (oxidative stress) > anti-AR > GR. A mitigation plan for WWTP operators based on EBT exceedance is proposed. This study demonstrates that the proposed effect-based monitoring battery is a complementary tool to the chemical analysis approach. A regular application of such time- and cost-effective bioanalytical tools in the WWTPs of the DRB is proposed to provide a ‘safety net’ for aquatic ecosystems.

Faster evapotranspiration recovery compared to canopy development post clearcutting in a floodplain forest

Actual evapotranspiration (ETa) is a key component of the water balance, and its accurate quantification of spatiotemporal variation is essential to improve the understanding of soil–plant-atmosphere-hydrosphere interactions. While in situ point measurements allow for the determination of the ETa of a particular ecosystem or land cover type, remote sensing methods make it possible to divide and evaluate the rate of ETa of different ecosystems in the landscape and would allow better management of the water resource system, especially if those are partly or permanently limited. The goal of this paper was to analyze the impact of clearcutting during standard forest management practices in floodplain forests and its effect on the water regime of the area. We selected the Lanžhot floodplain forest area (48.681°N 16.950°E, 155 m a.s.l.) that represents a biologically and hydrologically unique area of remnant floodplain forest within the upper Danube River basin. Since clearcutting represents a drastic intervention into the ecosystem including changes in canopy structure and local microclimate, we hypothesized that the impact of the clearcut on the overall water balance is long-term in the order of decades as a result consequence of logging of the mature forest and changes in local microclimatic conditions in disturbed areas. To analyze the impacts of clearcutting on ETa, we applied the METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) remote sensing model. METRIC was validated in the Central European climatic conditions using two ground eddy covariance measurements systems over grassland and floodplain forest. The evaluated model METRIC was then applied to quantify ETa in three areas of interest in the floodplain forest, where in 2015–2021, mature vegetation was targeted for removal, modification of the soil surface, and subsequent planting of a new generation of English oak trees (Quercus robur L.). Immediately after the removal of vegetation cover, METRIC detected an annual decrease in ETa by 35–40%, while leaf area index (LAI) decreased by 70–80%. This was followed by a quick recovery of the ETa/ETo (where ETo represents FAO-56 reference evapotranspiration), reaching similar values as uncut surrounding vegetation during the third year, while LAI recovery was detected in the fifth year after the removal of vegetation cover. The rapid recovery of the ETa/ETo rejected the initial hypothesis, and studies showed that the newly formed stand replaced the ETa/ETo rate of the mature stand in the floodplain forest conditions of Central Europe in the fourth year, suggesting that the impacts of clearcutting on the hydrology may be temporally relatively limited.

Towards the construction of representative regional hydro(geo)logical numerical models: Modelling the upper Danube basin as a starting point

Introduction: Pressure on groundwater resources is increasing rapidly by population growth and climate change effects. Thus, it is urgent to quantify their availability and determine their dynamics at a global scale to assess the impacts of climate change or anthropogenically induced pressure, and to support water management strategies. In this context, regional hydrogeological numerical models become essential to simulate the behavior of groundwater resources. However, the construction of global hydrogeological models faces a lot of challenges that affect their accuracy.Methods: In this work, using the German portion of the Upper Danube Basin (∼43,000 km2) we outline common challenges encountered in parameterizing a regional-scale groundwater model, and provide an innovative approach to efficiently tackle such challenges. The hydrogeological model of the Danube consists of the groundwater finite element code OpenGeoSys forced by the groundwater recharge of the surface hydrological model mHM.Results: The main novelties of the suggested approach are 1) the use of spectral analyses of the river baseflow and a steady state calibration taking as reference the topography to constraint the hydraulic parameters and facilitate the calibration process, and 2) the calibration of the hydraulic parameters for a transient state model by considering parameters derived from the piezometric head evolution.Discussion/conclusion: The results show that the proposed methodology is useful to build a reliable large-scale groundwater model. Finally, the suggested approach is compared with the standard one used by other authors for the construction of global models. The comparison shows that the proposed approach allows for obtaining more reliable results, especially in mountainous areas.

The Ichthyofauna of the Bednja River, Ichthyological ‘Hot Spot’ in the Danube Basin—Exceptional Diversity under Strong Threats

The Bednja River is the longest river flowing with its full course exclusively through Croatia and one of the largest right tributaries of the Drava River, which belongs to the Danube River basin. Due to the variety of habitats present within the course of the Bednja River, as well as older literature reports, it can be expected that this river harbors a high number of freshwater fish species and would likely benefit from conservation and preservation efforts. We compiled and analyzed the existing literature data on the Bednja River fish communities and performed field investigations at various localities on this river in order to describe the current structure of its freshwater fish fauna and monitor changes induced by human activities. Our results corroborate the presence of a rich and diverse fish community. Moreover, with 36 native species, the Bednja River harbors one of the richest fish communities in Croatia as well as in the Danube basin. Unfortunately, modifications of the native fish community were evident in the form of local extinctions, reductions in the population abundance of several native species and the presence of non-native species. Habitat degradation and fragmentation were identified as the most serious threats provoking negative effects on the native fish populations, followed by predatory and competitive effects of invasive species.

Petroleum play types and source rocks in the Pannonian basin, insight from the Slovak part of the Danube Basin

The Danube Basin represents a Miocene depocenter located on the NW margin of the Alpine-Pannonian-Carpathian region and is considered a partial sub-basin of the larger Pannonian Basin System. The gradual opening of the northern Slovak part of the basin during a 4-stage rifting event between the Badenian, Sarmatian (Langhian, Serravallian) to Pannonian (Tortonian) time reflected not only on the sedimentary fill and the development of volcanic fields but also on individual elements of the petroleum system. The presence of effective petroleum systems is supported by several gas and condensate deposits together with abundant hydrocarbon shows. The study offers new insight into the petroleum plays in Danube Basin based on new and vintage reflection seismic lines and organic geochemistry data. The novel findings reveal that within the older sub-basins (Blatné and Želiezovce) the main source rock is the lower Badenian mudstone with mixed Type III/II kerogen. Paleogene shales with Type II kerogen together with Pre-Cenozoic basement Type III/II rocks cannot be excluded. In the younger sub-basins (Komjatice and Gabčíkovo-Győr) the main source rocks are upper Badenian – Sarmatian, and Pannonian mudstones with Type III/II kerogen. Two gas play groups are defined. 1) Plays in older sub-basins characterized by structural traps mostly in the Badenian reservoirs. 2) Plays in younger sub-basins characterized by stratigraphic and structural traps in Sarmatian and Pannonian reservoirs. Non-hydrocarbon gas risk arises from CO2 and N2 contents sourced from buried volcanic fields. The volume of inert gasses trapped in particular sub-basins is dependent on the timing and type of volcanism. It is lower in the older sub-basins and higher in the younger ones, at the same time, the risk is lower in stratigraphically highest reservoir intervals.

Effects of different spatial and precipitation input data on swat-derived catchment features

Computer-based mathematical models are used in water management research to represent ecological problems, simulate different processes, deal with such problems and support their solution. Such studies require an interdisciplinary approach that is both user-friendly and comprehensive to integrate all of the processes that occur in nature. The use of available hydrological models requires a model setup with a reasonable level of data quality and quantity to represent catchment features to emphasize the distinctive local character of ecosystems. One of the models that comply with such requirements is the Soil and Water Assessment Tool (SWAT). This paper aims to address the possible impact of different spatial and precipitation input data on the catchment features by using SWAT for the case study of the floodplain located within the Danube River Basin in Serbia. The objective was to evaluate the impact of digital elevation models, land use, and soil types with different resolutions (1) SRTM and ASTER (30 m), TanDEM-X (12.5 m), (2) CORINE and GlobCover land use databases, and (3) FAO/UNESCO world soil map and digitized soil map of Vojvodina Province on catchment delineation. The research was conducted alongside the analysis of precipitation, using data from the CFSR, CarpatClim, and the national yearbooks. Regarding the spatial data, the results indicate that the high-resolution data need to be adjusted for this area, while the ASTER layer is suitable at an acceptable level for further modeling in SWAT. Interpolated precipitation data are better to use due to their higher resolution (10km) and the heterogeneous distribution of rain gauge stations.

The parasites of a successful invader: monogeneans of the Asian topmouth gudgeon Pseudorasbora parva, with description of a new species of Gyrodactylus.

Monogenean parasites are often co-introduced with their fish hosts into novel areas. This study confirmed co-introduction of two dactylogyrids, Dactylogyrus squameus Gusev, 1955 and Bivaginogyrus obscurus (Gusev, 1955), and a newly described gyrodactylid species, Gyrodactylus pseudorasborae n. sp. into Europe along with their fish host, the invasive topmouth gudgeon Pseudorasbora parva (Temminck & Schlegel) from East Asia. All three species were observed in the lower Dnieper and middle Danube basin regions and had slightly larger haptoral hard parts than the same parasites in their native range. While dactylogyrids occurred sporadically, we recorded regular infection by G. pseudorasborae n. sp. at relatively high prevalence and abundance. This latter species was observed in both the native and non-native range of topmouth gudgeon, and resembles Gyrodactylus parvae You et al., 2008 recently described from P. parva in China. Both species were distinguished based on genetic analysis of their ITS rDNA sequence (6.6% difference), and morphometric differences in the marginal hooks and male copulatory organ. Phylogenetic analysis of dactylogyrid monogeneans showed that B. obscurus clustered with Dactylogyrus species parasitising Gobionidae and Xenocyprididae, including D. squameus, supporting recent suggestions of a paraphyletic origin of the Dactylogyrus genus. In addition to co-introduced parasites, topmouth gudgeon was infected with a local generalist, G. prostae Ergens, 1964, increasing the number of monogeneans acquired in Europe to three species. Nevertheless, monogenean infections were generally lower in non-native host populations, potentially giving an advantage to invading topmouth gudgeon.

Wide-scope target screening characterization of legacy and emerging contaminants in the Danube River Basin by liquid and gas chromatography coupled with high-resolution mass spectrometry

A state-of-the-art wide-scope target screening of 2,362 chemicals and their transformation products (TPs) was performed in samples collected within the Joint Danube Survey 4 (JDS4) performed in 2019. The analysed contaminants of emerging concern (CECs) included three major categories: plant protection products (PPPs), industrial chemicals and pharmaceuticals and personal care products (PPCPs). In total, 586 CECs were detected in the samples including 158 PPPs, 71 industrial chemicals, 348 PPCPs, and 9 other chemicals. A wide-variety of sample matrices were collected including influent and effluent wastewater, groundwater, river water, sediment and biota. Forty-five CECs (19 PPPs, 8 industrial chemicals, 18 PPCPs) were detected at levels above their ecotoxicological thresholds (lowest predicted no-effect concentration (PNEC) values) in one or more of the investigated environmental compartments, indicating potential adverse effects on the impacted ecosystems. Among them 12 are legacy substances; 33 are emerging and qualify as potential Danube River Basin Specific Pollutants (RBSPs). Moreover, the efficiency of the wastewater treatment plants (WWTPs) was evaluated using 20 selected performance indicator chemicals. WWTPs showed effective removal (removal rate ≥80%) and medium removal (removal rate 25–80%) for 6 and 8 of the indicator chemicals, respectively. However, numerous contaminants passed the WWTPs with a lower removal rate. Further investigation on performance of WWTPs is suggested at catchment level to improve their removal efficiency. WWTP effluents are proven to be one of the major sources of contaminants in the Danube River Basin (DRB). Other sources include sewage discharges, industrial and agricultural activities. Continuous monitoring of the detected CECs is suggested to ensure water quality of the studied area.