Danube Research Articles

Presence and Distribution of Sun-Blocking Agents in the Danube River: Implications for Aquatic Ecosystem Health

Organic sun-blocking agents are recognized as emerging pollutants of the aquatic environment. The consequences and effects of these harmful substances on aquatic organisms are not fully understood, particularly in the context of Romania. This study examines the presence and environmental hazards posed by ten UV filters found in the Danube River. Six of the ten targeted contaminants were detected in surface water samples: 2-hydroxy-4-methoxy-benzophenone (BP-3), 2,4-dihydroxy benzophenone (BP-1), 2,3,4-trihydroxy benzophenone (234HBP), 2,2′-dihydroxy-4-methoxy-benzophenone (BP-8), 2-hydroxy-4-methoxy-4′-methyl-benzophenone (BP-10), and benzyl salicylate (BS). In sediment samples, seven of the ten compounds were identified: BS, BP-3, 4-hydroxybenzophenone (4HBP), BP-1, 234HBP, 2,2′,4,4′-tetrahydroxybenzophenone (BP-2), and BP-10, with different frequencies. The correlation coefficients showed strong relationships between benzophenone derivatives in surface water samples and a common contamination source for BP-3 and BS in sediment samples. In the assessment, the risk quotient (RQ) for BP-1 in fish was determined to be 1.81. Similarly, RQ values for BP-3 were calculated as 1.24 for Daphnia magna and 57 for fish, suggesting that these UV filters could potentially present substantial hazards to the aquatic ecosystem. The study findings indicate that additional research is needed to investigate the presence and potential risks of organic sun-blocking agents in surface waters, with a particular emphasis on densely populated areas in Romania.

Distribution of selenium: A case study of the Drava, Danube and associated aquatic biotopes

This paper presents the results of the research on the overall distribution of selenium (Se) in various aquatic compartments (water, sediment, plankton and macrophytes) at six selected sites of the Croatian part of the Drava and Danube rivers, the connected floodplain lake and the melioration channel system carried out in two sampling periods (flooding in June and the drought period in September). In addition, the physicochemical water properties, plankton composition and biomass were analysed. Our study revealed low mean Se contents in sediments and water, indicating Se deficiency in the studied freshwater systems. The physicochemical environment, including Se distribution, was primarily influenced by hydrology rather than site-specific biogeochemical and morphological characteristics. The flooding period was characterised by higher Se content in water and higher transparency, nitrate and total nitrogen concentrations than drought conditions. At the river sites, sediment Se content was the highest during the flood period, while at all other sites, higher concentrations were found during the drought, reaching the maximum in the lake. Although Se concentrations were below the threshold for aquatic ecotoxicity, they increased in the following order: water (0.021–0.187 μg Se L−1) < sediments (0.005–0.352 mg Se kg−1) < macrophytes (0.010–0.413 mg Se kg−1) < plankton (0.044–0.518 mg Se kg−1) indicating its possible biomagnification at the bottom of the food chain. Species known for high Se accumulation potential dominated the biomass of the main plankton groups and the composition of the macrophyte community, which may provide a more sensitive and accurate steady-state compartment monitor for Se assessment in freshwater biotopes.

A harmonized Danube basin-wide multi-compartment concentration database to support inventories of micropollutant emissions to surface waters

BackgroundThe European Water Framework Directive foresees the establishment of emission inventories for micropollutants (MP) to facilitate an evidence-based development of mitigation measures. Regionalized pathway analysis constitutes a moderately data-intensive approach to quantify the contribution of different pathways to the total pollution of surface waters. So far, only few European member states have created an inventory that includes diffuse pathways. The fundamental basis to enable it is an accessible, well-structured and harmonized database with data on the concentration of MPs in multiple compartments, such as soils, groundwater, atmospheric deposition and urban systems. Combined with the water and suspended substance balance in river basins, such data enables the estimation of emission loads via specific pathways. In the Danube River Basin, but in general in Europe, a public data management platform with such scope and criteria is still lacking.ResultsWe collected and harmonized MP measurements across multiple compartments and countries together with key metadata, harmonized and combined them into a new database. The resulting tool, available for download, facilitates the assessment of current data availability, in terms of quantity and quality. For example, while the majority of available data stems from groundwater and surface water, other highly relevant compartments are scarcely represented. By examining differences in MP concentration level across compartments, the database can lead to understand the relevance of specific emission pathways and thus to prioritize data-retrieval and calculation efforts in modelling applications. Selected examples show how to exploit the metadata associated to the measurements to extrapolate the results to regions not covered by specific monitoring programmes. For example, PFAS concentrations in treated wastewater show significant dependence on the design capacity of the treatment plant.ConclusionsThis study showcases how such database can support the setup of emission inventories, guide data providers and national authorities in prioritizing the allocation of resources for new surveys and in optimizing their national data collection and management systems. The process tested showed a great need for enhanced data literacy across countries and institutions to increase data availability and quality to secure the exploitation of the full information potential generated via monitoring programmes.

History, Life History, and Fate of a Salmonid Flagship Species: The Danube Salmon

The Danube Salmon Hucho hucho, endemic to the Danube River basin, is one of the largest members of the salmonid family. Here, we describe the distribution, ecology, and status of this flagship species in the upper Danube River basin. We model the historical distribution of Danube Salmon in the Austrian Danube River basin based on a review of the literature and species records. Fish sampling data over the past few decades illustrate the dramatic decline of the species and the population characteristics within the ecological niche that the species occupies. In conclusion, measures for the long‐term conservation of Danube Salmon in the upper Danube River, as well as possibilities for sustainable management, are addressed and discussed.

Morphologic Adjustment of a River Reach with Groynes to Channel Bypassing

AbstractThis article is focused on the investigation of the spatio-temporal variability of the Danube River reach’s vertical accretion thickness due to the response of the Danube River reach to bypassing. Five groyne-induced benches (GIBs) of the bypassed channel developed after water diversion in 1992 was studied by changes in topography for three-time spans (for the original gravel surface, for the surface before the 2013 flood and for the surface after the 2013 flood). The allostratigraphic approach was applied to 548 drilling probes at all GIBs and toptop, supra-platform, tail and backchannel geomorphic units have been identified at each GIB. The main to side-channel system connectivity increase sedimentation rates and the accretion was controlled by large flood events. The 100-year flood in 2013 contributed to the total volume by almost 26%. During study period 1992–2017, totally 1,146,589 m3 was accreted on five GIBs, of this 209,752 m3 during flood event in 2013 and 267,700 m3 in post flood period 2014–2017. The top geomorphic unit exhibits the highest median values of vertical accretion and for all GIBs accretion thickness are not related to the height above the mean channel water level. The thickness of accretion varied, likely because the variability of the vegetation cover caused variable hydraulic conditions and accretion rate span from 3.8 cm.year−1 to 5.3 cm.year−1. The investigation of the sediment thickness over long time spans 24 years and a large flood event) allowed us to conclude that the thickness is spatially variable for individual GIBs; however, its trend over time remains constants depending on the intake of sediments during large floodsd events. This article also provides a methodological template for the detailed investigation of river channel adjustment due to bypassing.

Electrochemical Sensing of Cadmium and Lead Ions in Water by MOF-5/PANI Composites.

For the first time, composites of metal-organic framework MOF-5 and conjugated polymer polyaniline (PANI), (MOF-5/PANI), prepared using PANI in its conducting (emeraldine salt, ES) or nonconducting form (emeraldine base, EB) at various MOF-5 and PANI mass ratios, were evaluated as electrode materials for the electrochemical detection of cadmium (Cd2+) and lead (Pb2+) ions in aqueous solutions. Testing of individual components of composites, PANI-ES, PANI-EB, and MOF-5, was also performed for comparison. Materials are characterized by Raman spectroscopy, scanning electron microscopy (SEM) and dynamic light scattering (DLS), and their electrochemical behavior was discussed in terms of their zeta potential, structural, morphology, and textural properties. All examined composites showed high electrocatalytic activity for the oxidation of Cd and Pb to Cd2+ and Pb2+, respectively. The MOF/EB-1 composite (71.0 wt.% MOF-5) gave the highest oxidation currents during both individual and simultaneous detection of two heavy metal ions. Current densities recorded with MOF/EB-1 were also higher than those of its individual components, reflecting the synergistic effect where MOF-5 offers high surface area for two heavy metals adsorption and PANI offers a network for electron transfer during metals' subsequent oxidation. Limits of detection using MOF/EB-1 electrode for Cd2+ and Pb2+ sensing were found to be as low as 0.077 ppm and 0.033 ppm, respectively. Moreover, the well-defined and intense peaks of Cd oxidation to Cd2+ and somewhat lower peaks of Pb oxidation to Pb2+ were observed at voltammograms obtained for the Danube River as a real sample with no pretreatment, which implies that herein tested MOF-5/PANI electrodes could be used as electrochemical sensors for the detection of heavy metal ions in the real water samples.

Plant Remains and What Else? Environmental Archaeology of the Late Hellenistic Pit Fills of Sexaginta Prista, Northern Bulgaria

ABSTRACT This study combines several categories of environmental remains retrieved from machine-assisted water flotation samples, originating from the pit field of the Late Hellenistic archaeological site of Sexaginta Prista (2c. BC – 1c. AD), located on the River Danube in North Bulgaria. The analysis of the different organic remains, such as archaeobotanical macro-remains (seeds, wood charcoal and ‘food crusts’), fish scales, molluscs and animal bones, aims at exploring the possible utilisation scenarios of the pits, including crop/food storage and preparation, disposal activities and ritual practices and also allowed for a preliminary past-environmental reconstruction of the site during the study of interest.

Dipsacus gmelinii (Caprifoliaceae), a wetland species new to the Bulgarian flora

Abstract Dipsacus gmelinii is here reported as a new addition to the vascular flora of Bulgaria. It was recorded on Belene Island, in the Danube River. In the present paper, the species is described morphologically with an emphasis on carpomorphological characters. The distinctive differences from related species of the genus are also highlighted. Additionally, ecological conditions and floristic composition at the localities of the species, and phytosociological relationships of the communities in which it participates are discussed.

Are extreme floods on the Danube River becoming more frequent? A case study of Bratislava station

Abstract In this study, strong and extreme flood events were analysed on the basis of long-term daily runoff records of winter and summer floods in the Danube River between 1876 and 2020, using the peaks-over-threshold method. Based on the results, the following conclusions can be made: (1) There is a downward trend in strong winter floods, but it is not statistically significant. Additionally, there is an upward trend in summer floods, but this is not statistically significant. (2) There are statistically significant upward trends in extreme events for both the winter and summer seasons. The results have implications for flood protection and disaster management on the Danube River. Regulation of assets in flood-prone areas is essential for minimising economic damage. Public awareness of increasing extreme summer floods is vital for prevention. This study suggests that effective flood risk analysis requires (i) a local- to regional-scale approach to account for spatial variability and (ii) advanced statistical tools for robust detection of climate extremes and estimation of their occurrence rates.

Accumulation of microplastics in Zebra mussel (Dreissena polymorpha, Pallas, 1771) in the sand pit lake Kazichene, Bulgaria

In recent years, microplastic contamination has received worldwide distribution and specific attention. As a result, detecting sensitive bioindicators is crucial to establish the pollution. The aim of the present study is to investigate the accumulation of microplastics in zebra mussels (Dreissena polymorpha, Pallas, 1771) from the sand pit lake Kazichene. The natural range of the zebra mussel in Bulgaria includes the Danube River delta, the Black Sea rivers and coastal lakes. However, it is considered a wide spread invasive species to inland freshwaters. The use of invasive species as bioindicators over native species is advisable in order to protect the local biodiversity. In total 20 mussels of D. polymorpha were used for the analysis. The biological tissues of the mussels were digested with the aid of 30% H2O2 at 65°C for 24 - 48 hours. Microplastics (772 pcs. in total) were detected in all zebra mussel samples, indicating microplastic contamination in Lake Kazichene. Three main shapes have been identified: fragments, fibres and pellets, with the highest proportion of the fragments. The colours of the microplastic particles found were black, red, yellow and transparent, dominated by those of black colour, followed by red. The length of the fibres found in the zebra mussels ranged from 0.25 to 5 mm. There was no strong correlation between the body length/meat weight of zebra mussels with the degree of microplastic accumulation in the mussels.

Linking antibiotic resistance gene patterns with advanced faecal pollution assessment and environmental key parameters along 2300 km of the Danube River

The global spread of antimicrobial resistance (AMR) in the environment is a growing health threat. Large rivers are of particular concern as they are highly impacted by wastewater discharge while being vital lifelines serving various human needs. A comprehensive understanding of occurrence, spread and key drivers of AMR along whole river courses is largely lacking. We provide a holistic approach by studying spatiotemporal patterns and hotspots of antibiotic resistance genes (ARGs) along 2311 km of the navigable Danube River, combining a longitudinal and temporal monitoring campaign. The integration of advanced faecal pollution diagnostics and environmental and chemical key parameters allowed linking ARG concentrations to the major pollution sources and explaining the observed patterns. Nine AMR markers, including genes conferring resistance to five different antibiotic classes of clinical and environmental relevance, and one integrase gene were determined by probe-based qPCR. All AMR targets could be quantified in Danube River water, with intI1 and sul1 being ubiquitously abundant, qnrS, tetM, blaTEM with intermediate abundance and blaOXA-48like, blaCTX−M-1 group, blaCTX−M-9 group and blaKPC genes with rare occurrence. Human faecal pollution from municipal wastewater discharges was the dominant factor shaping ARG patterns along the Danube River. Other significant correlations of specific ARGs were observed with discharge, certain metals and pesticides. In contrast, intI1 was not associated with wastewater but was already established in the water microbiome. Animal contamination was detected only sporadically and was correlated with ARGs only in the temporal sampling set. During temporal monitoring, an extraordinary hotspot was identified emphasizing the variability within natural waters. This study provides the first comprehensive baseline concentrations of ARGs in the Danube River and lays the foundation for monitoring future trends and evaluating potential reduction measures. The applided holistic approach proved to be a valuable methodological contribution towards a better understanding of the environmental occurrence of AMR.

Connectivity of Geochemical Composition of Sediments and Soils in the Large Urban River Catchment

ABSTRACT This article aimed to identify sources and transport pathways of macro- and microelements in large urbanized rivers under significant anthropogenic pressure. To achieve the objective of this study, the geochemical characteristics of the sediments of the Sava and Danube Rivers and the soils flooded by the Kolubara River were determined. The high content of Mg indicates the dominant origin of the material from loess deposits. The significantly higher contents of Cr and Ni in sediment and soil samples from the Obrenovački Zabran (OZ) than in the samples from the Veliko Ratno Ostrvo (VRO) are the result of increased anthropogenic pressure. Sediments from the VRO show increased Sn and Sb contents. The increase in the content of chalcophile elements is the highest in the sediments from the OZ and ranges from 1.8 to 2.7 times, compared to their concentrations in the Earth’s crust. The soils from OZ and the sediments from the VRO show a decrease in the content of chalcophile elements compared to the sediments from the OZ so the increase is 1.2–1.5, and 0.9–2.3 times, respectively compared to the Earth’s crust. The obtained results revealed that the yield of sedimentary material that has higher concentrations of microelements decreases already at a distance of several km.

Three hundred years of past and future changes for native fish species in the upper Danube River Basin—Historical flow alterations versus future climate change

AbstractAimRivers belong to the most threatened ecosystems on Earth. Historical anthropogenic alterations have, and future climate change will further affect rivers and the species therein. While many studies have projected climate change effects on species, little is known about the severity of these changes compared to historical alterations. Here, we used a unique 300‐year time series of hydrological and climate data to explore the vulnerability of 48 native fish species in the upper Danube River Basin to past and potential future environmental changes.LocationUpper Danube River Basins (Germany and Austria).MethodsWe applied a climate niche factor analysis and calculated species‐specific vulnerability estimates based on modelled and observed hydrological and climate data from 1800 to 2100. We compared the estimated species vulnerabilities between two historical time intervals (1800–1830 and 1900–1930) and a future time interval (2070–2100, including the two representative concentration pathways 4.5 and 8.5) to an observed reference time interval (1970–2000). In addition, we identified the main environmental drivers of species vulnerability and their change over the past 200 years and for the predicted 100 years in the future.ResultsOur results showed that (i) in the past, species vulnerability was mainly driven by changes in discharge, while (ii) future potential vulnerabilities would be due to temperature. Moreover, we found that (iii) future environmental conditions for riverine fish species driven by temperature would change at a similar magnitude as past hydrological changes, driven by anthropogenic river alterations. Future changes, projected for the RCP 4.5, would result in moderate species vulnerability, whereas for the RCP 8.5, the vulnerability for all species would substantially increase compared to the historical conditions.Main ConclusionAccounting for an extended timeline uncovers the extent of historical pressures and provides unprecedented opportunities to proactively plan conservation strategies that are necessary to address future challenges.

EDNA metabarcoding reveals the role of habitat specialization and spatial and environmental variability in shaping diversity patterns of fish metacommunities.

Information is scarce on how environmental and dispersal processes interact with biological features of the organisms, such as their habitat affinity, to influence patterns in biodiversity. We examined the role of habitat specialist vs. generalist species, and the spatial configuration, connectivity, and different environmental characteristics of river-floodplain habitats to get a more mechanistic understanding of alpha and beta diversity of fish metacommunities. We used environmental DNA metabarcoding to characterize species (taxa) richness and composition in two separate floodplains of the river Danube (Austria and Hungary) during two different hydrological conditions. Results showed that differences in the number of generalist and specialist species and their responses to connectivity and environmental gradients influenced patterns in alpha and beta diversity. Of the components of beta diversity, richness difference (nestedness) showed consistently higher values than replacement (turnover), mainly due to the decrease of specialist species along the connectivity gradient (i.e., from the mainstem to the most isolated oxbows). Variance in both alpha and beta diversity could be well predicted by a set of local and regional variables, despite high environmental variability, which characterizes river-floodplain ecosystems. Of these, the joint or shared variance fractions proved to be the most important, which indicates that the effects of local and regional processes cannot be unambiguously separated in these river-floodplain systems. Local scale environmental variables were more important determinants of both alpha and beta diversity in the low water period than in the high water period. These results indicate the differential role of local and regional processes in community organization during different hydrological conditions. Maintenance of both local and regional scale processes are thus important in the preservation of alpha and beta diversity of floodplain fish metacommunities, which should be considered by environmental management.

EVALUATION OF CHEMICAL INDICATORS OF ANTHROPOGENIC INFLUENCE IN THE LOWER DANUBE BASIN

The article explores the nature and trends of hydrochemical parameter connection and changes in the Lower Danube basin. The research examines nitrogen and phosphorus compounds, dissolved oxygen, and biochemical oxygen demand as indicators of anthropogenic influence and surface water quality alterations. The study was conducted between 2015 and 2023 at three sampling points: the Reni and Vilkovo water intakes on the Danube River and the Yalpuh Reservoir, which is connected to the Danube. The study employed mathematical statistics approaches. The research established changes in annual median values, investigated correlation links between chemical components by Spearman correlation, and implemented factor analysis by minimizing residuals. A spatiotemporal analysis of chemical components indicative of anthropogenic impact on the Lower Danube surface water revealed notable changes in the basin during 2019-2021. These changes were manifested as a sharp increase in ammonium concentrations and phosphate growth since 2020-2021, an abnormal decrease in dissolved oxygen concentration in 2019, a decrease in BOD within Yalpuh to the Danube BOD level, and a shift in trends from decreasing to increasing for nitrites. The water quality class also changed. Currently, the Danube River water is of the third quality class for nitrates, phosphates, and ammonium. In the Yalpuh Reservoir, it is of the 2nd class for nitrogen compounds and the 3rd class for phosphates. Two principal groups of chemical components are identified based on their underlying causes and sources, as revealed by correlation and factor analysis. A consistent relationship is observed between ammonium and phosphates across all monitoring sites, suggesting their role as pollutants entering surface waters via wastewater discharge and agricultural runoff and representing the main anthropogenic impact factor. The Danube River displays a specific relationship between nitrates and dissolved oxygen, reflecting the seasonal fluctuations in their concentrations and their underlying causes of changes, which stem from both anthropogenic and natural processes.

Morphometric characteristics of spiny-cheek crayfish Faxonius limosus (Rafinesque, 1817) from the Danube River on the territory of Serbia

Twenty-three morphometric characteristics of spiny-cheek crayfish Faxonus limosus from Danube, Serbia, were analyzed to describe the general body shape. Forty-eight specimens were caught in May 2022 and January 2023 and measured for morphometric variation. Also, the values of two crayfish condition indices, Fulton?s condition factor (FCF) and crayfish constant (CC), were determined. Most of the analyzed characteristics were moderately variable (CV 10-30%). Principal component analysis (PCA) was applied to the morphological measurements. All the variables make similar contributions to the variance of the first principal component. The highest contributions are from variables CEF and ARL. ARW, CPH, ABH, CPW, and ROW significantly contributed to the second principal component variance. The population of spiny-cheek crayfish at the investigated site has a relatively stable age structure.

Analysis of dynamic features on local fatigue cracks in steel bridges

In steel bridges with orthotropic decks, a common and important engineering structure, fatigue cracks can appear under long-term operation. Existing artificial detection is the main approach to detecting fatigue cracks in steel bridges, in addition to some non-destructive testing or image processing methods, and unmanned aerial vehicle are applied to improve accuracy and efficiency. However, the detection of fatigue cracks in steel bridges based on the variation of dynamic responses or dynamic parameters is another attractive idea, which is still rarely mentioned and investigated in the international literature. The reason is that local cracks usually have negligible effect on the global dynamic characteristics of steel bridges, resulting in the insensitivity to dynamic indexes to fatigue cracks. On this occasion, this study numerically explores and establishes two sensitive damage features to local damage, i.e., the crack in the vertical rib, based on the fatigue cracks found on the Türr Istvan bridge over the Danube River in Hungary. The local vibrations of the bridge are excited through the local impact on the structural details, i.e., the vertical rib, and then the high-order frequencies of the entire bridge are examined. The obtained high-order frequencies are proved to be more sensitive to the fatigue cracks on vertical ribs and increased with the crack depths. On the other hand, the correlation of the stress curves on opposite sides of the crack is sensitive to the depth of the crack. If fatigue cracks are found, the development degree of the fatigue cracks can be monitored more accurately by focusing on the correlation of local stresses near the crack. These two damage features are numerically proven to have feasibility and are expected to break through the insensitivity of the existing dynamic detection methods.

Heavy mineral catalogue for the characterization and provenance of red sandstone macrolithic tools from Hódmezővásárhely-Gorzsa

Although ground stone tools (GSTs) are among the most abundant stone tools in archaeological sites, they are rarely investigated both from the archaeological and the geological point of view. There are many pieces made of siliciclastic sedimentary raw material. Their fragmentary condition makes it possible to examine them by slightly destructive methods, such HMA (heavy mineral analysis), which was developed primarily for siliciclastic rocks. Until now, ‘sensu stricto’ (s.str) heavy mineral analysis has not yet been carried out for ground stone tools, neither at the national nor at the international level. By comparing the heavy mineral compositions of the stone tools and their potential raw materials with the help of a newly developed HM descriptive system (including rutile, zircon, tourmaline, apatite and titanite), it is possible to determine the provenance of these archaeological materials. From the Neolithic tell of Gorzsa, 109 red sandstone macrolithic stone tools are known. These were separated into four, different types (‘Red–1’ – ‘Red–4’), based on the macroscopic and microscopic analysis. 11 fragments were chosen for HMA analysis. In addition, red-coloured sandstones from different geological occurrences of the Carpathian-Pannonian Basin (22 pieces) were also investigated. Based on the heavy mineral analysis, all raw material types of the stone tools could be originated from the Maros River and the Apuseni Mountains (Transylvania). However, the previously determined potential sources (Permotriassic and Miocene sequences from the Mecsek Mountains, Balaton Highlands, pebbles from the Danube River, and Papuk Mountains) cannot be excluded with absolute certainty from the possible raw materials.

Water quality evaluation of the Danube River basin in Bačka (northern Serbia) using multivariate statistical techniques

The study aimed to analyze changes in water quality based on ten physicochemical parameters for the Danube River in Bačka. Data from three profiles over a twenty-year interval were used and processed using multivariate statistics. An ANOVA indicated that the quality of surface water is mostly at a satisfactory level. Sufficient amounts of dissolved oxygen indicate a favorable aeration regime. The surpassing of the annual and monthly values of suspended solids was recorded for all profiles (especially in summer). The summary results show that most parameters, except for suspended solids, are within the allowed values for water quality Class II. A Pearson’s correlation test indicates a moderate to weak correlation of the analyzed parameters. A PCA analysis determined the influence of (a) eutrophication processes; (b) ecological factors; and (c) concentrated sources of pollution. Changes in the Danube’s water quality, primarily increased concentrations of suspended solids, can exert a limiting influence on some economic activities and their planning.

Danube anadromous sturgeons male to female ratio research in the context of solutions development that address the discontinuity of their historical migration routes due to hydrotechnical constructions

Historical migration routes for anadromous sturgeons in the Danube River have been interrupted by transversal structures for hydropower use, from which the Iron Gates hydropower system represents the first significant barrier upstream Danube from the Black Sea. For the implementation of DALIA project, funded by Horizon Europe, the National Institute for Research and Development in Environmental Protection Bucharest (INCDPM) carries out research and innovation activities that aim to provide a sustainable solution for ultrasonic tagged sturgeons to by-pass upstream and downstream the hydropower dams. The spatial and temporal parameters recorded during April 2024 for the behavior of 7 male and 2 female ultrasonic tagged sturgeon specimens was analyzed and incorporated in a decisional matrix that provided the value 4 to 1 for the male to female ratio. This result is taken into account in the design for the by-pass solutions to be implemented for the dams that will provide the restoration of the historical multisecular migration route for ultrasonic tagged sturgeon species.