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Charting a course for freshwater biomonitoring: The grand challenges identified by the global scientific community
Urban Aquatic Nature-Based Solutions in the Context of Global Change: Uncovering the Social-ecological-technological Framework
Different intensities and directions of hyporheic water exchange in habitats of aquatic Ranunculus species in rivers—a case study in Poland
Response of Aquatic Plants to Extreme Alterations in River Morphology
In this study, we aimed to identify the macrophyte pattern and diversity under exposure to substantial hydromorphological degradation in rivers, taking into account the water quality factor. The study was based on 190 small and medium lowland rivers in Poland that had experienced channel alterations. The number of taxa identified (153 species) was consistent with natural/seminatural rivers, and the average species richness for the survey site was 16. Nevertheless, nearly 25% of the survey sites were poor in species for which ten or fewer taxa were noted. The most common species were emergent Phalaris arundinacea; free-floating Lemna minor; heterophyllous Sparganium emersum; filamentous algae Cladophora sp.; and some amphibious species, including Agrostis stolonifera. The surveyed sites represented a wide diversity gradient, from sites poor in species and with low diversity based on relative abundance to highly diverse river sites in less transformed rivers. Our results revealed that macrophyte species were mostly determined by hydromorphological degradation, as well as other distinguished environmental factors, such as water trophy (e.g., Lemna gibba, Bidens tripartita, and Ceratophylum demersum) and channel dimensions (e.g., Nuphar lutea, Sagittaria sagittifolia, and Typha latiflolia).
Take a photo of the river! Assessing the feasibility of using Google Street View images as source materials for assessing river hydromorphology
Origin, genetic structure and evolutionary potential of the natural hybrid Ranunculus circinatus × R. fluitans
AbstractUnderstanding the genetic variability of hybrids provides information on their current and future evolutionary role. In this paper, we focus on the interspecific hybridRanunculus circinatus × R. fluitansthat forms spontaneously within the groupRanuculusL. sect.BatrachiumDC. (Ranunculaceae Juss.). Genome-wide DNA fingerprinting using amplified fragment length polymorphisms (AFLP) was employed to determine the genetic variation among 36 riverine populations of the hybrid and their parental species. The results demonstrate a strong genetic structure ofR. circinatus × R. fluitanswithin Poland (Central Europe), which is attributed to independent hybridization events, sterility of hybrid individuals, vegetative propagation, and isolation through geographical distance within populations. The hybridR. circinatus × R. fluitansis a sterile triploid, but, as we have shown in this study, it may participate in subsequent hybridization events, resulting in a ploidy change that can lead to spontaneous fertility recovery. The ability to produce unreduced female gametes of the hybridR. circinatus × R. fluitansand the parental speciesR. fluitansis an important evolutionary mechanism inRanunculussect.Batrachiumthat could give rise to new taxa.
Assessing the sensitivity of urban aquatic nature-based solutions to hydroclimate variability using stable water isotopes
Abstract Natural and engineered water features, or blue infrastructure are increasingly implemented in cities as a form of water-related nature-based solutions (aquaNBS), to address ecological and hydrological challenges that threaten urban biodiversity and water security. Nevertheless, the combination of impacts from climate change, multi-faceted consequences of past management, current urban expansion, population growth, and overall urban ecosystem complexity makes it challenging to evaluate the hydrological function of these aquaNBS, and their sensitivity to hydroclimatic and other environmental changes. To enhance adaptation capacity of aquaNBS towards multiple urban and climatic stressors, it is crucial to understand the main hydrologic processes, as well as hydroclimate influences, that determine the functioning of aquaNBS. Stable water isotopes have proven to be a valuable tool in providing integrated understanding of hydrologic functioning over extended spatial scales. While higher frequency isotope data is usually most informative, even limited isotopic data can aid hydrological characterization. We conducted seasonal sampling over the period of one year in 2023/2024, across a major hydroclimate gradient across four European cities (Poznań, Berlin, Antwerp, Lisbon). The goal was to identify the dominant physical processes (in terms of water sources, dominant flow paths, and age proxies) linked to the main hydroclimate factors along a continental climate gradient. Comparative analyses of local stable water isotope signatures from different aquaNBS types (i.e., streams, ponds) revealed the strong influence of local hydroclimate, as well as varying water source contributions and mixing processes. The application of transit time proxies, such as tracer damping and young water fraction estimations, suggests ponds to be more sensitive to hydroclimate changes, as evidenced by the strong seasonality in evaporative enrichment and high fractions of young water contributions. In contrast, most streams indicated greater mixing of water sources and longer transit times, suggesting greater resilience to hydroclimate variability. In addition, a comparison between seasonally sampled data and monthly sampling for selected locations in Berlin showed that even relatively coarse temporal data collection, but with more extensive spatial coverage, can be sufficient and still insightful for broader hydrologic characterizations of aquaNBS at larger scales.
Predicting freshwater biological quality using macrophytes: A comparison of empirical modelling approaches
AbstractDifficulties have hampered bioassessment in southern European rivers due to limited reference data and the unclear impact of multiple interacting stressors on plant communities. Predictive modelling may help overcome this limitation by aggregating different pressures affecting aquatic organisms and showing the most influential factors. We assembled a dataset of 292 Mediterranean sampling locations on perennial rivers and streams (mainland Portugal) with macrophyte and environmental data. We compared models based on multiple linear regression (MLR), boosted regression trees (BRT) and artificial neural networks (ANNs). Secondarily, we investigated the relationship between two macrophyte indices grounded in distinct conceptual premises (the Riparian Vegetation Index — RVI, and the Macrophyte Biological Index for Rivers — IBMR) and a set of environmental variables, including climatic conditions, geographical characteristics, land use, water chemistry and habitat quality of rivers. The quality of models for the IBMR was superior to those for the RVI in all cases, which indicates a better ecological linkage of IBMR with the stressor and abiotic variables. The IBMR using ANN outperformed the BRT models, for which the r-Pearson correlation coefficients were 0.877 and 0.801, and the normalised root mean square errors were 10.0 and 11.3, respectively. Variable importance analysis revealed that longitude and geology, hydrological/climatic conditions, water body size and land use had the highest impact on the IBMR model predictions. Despite the differences in the quality of the models, all showed similar importance to individual input variables, although in a different order. Despite some difficulties in model training for ANNs, our findings suggest that BRT and ANNs can be used to assess ecological quality, and for decision-making on the environmental management of rivers.
Diversification of macrophytes within aquatic nature-based solutions (NBS) developing under urban environmental conditions across European cities
Understanding ecohydrology and biodiversity in aquatic nature-based solutions in urban streams and ponds through an integrative multi-tracer approach
Abstract. Rapid urbanization and climate change affect ecohydrology, biodiversity, and water quality in urban freshwaters. Aquatic nature-based solutions (aquaNBSs) are being widely implemented to address some of the ecological and hydrological challenges that threaten urban biodiversity and water security. However, there is still a lack of process-based evidence of ecohydrological interactions in urban aquaNBSs and their relationship to water quality and quantity issues at the ecosystem level. Through a novel, integrative multi-tracer approach using stable water isotopes, hydrochemistry, and environmental DNA we sought to disentangle the effects of urbanization and hydroclimate on ecohydrological dynamics in urban aquaNBSs and understand ecohydrological functioning and the future resilience of urban freshwaters. Stable isotopes and microbial data reflected a strong influence of urban water sources (i.e., treated effluent, urban surface runoff) across stream NBSs. The results show potential limitations of aquaNBS impacts on water quality and biodiversity in effluent-impacted streams, as microbial signatures are biased towards potentially pathogenic bacteria. Urban ponds appear to be more sensitive to hydroclimate perturbations, resulting in increased microbial turnover and lower microbial diversity than expected. Furthermore, assessment of macrophytes revealed low diversity and richness of aquatic plants in both urban streams and ponds, further challenging the effectiveness of NBSs in contributing to aquatic diversity. This also demonstrates the need to adequately consider aquatic organisms in planned restoration projects, particularly those implemented in urban ecosystems, in terms of habitat requirements. Our findings emphasize the utility of integrated tracer approaches to explore the interface between ecology and hydrology and provide insights into the ecohydrologic functioning of aquaNBSs and their potential limitations. We illustrate the benefit of coupling ecological and hydrological perspectives to support future NBS design and applications that consider the interactions between water and the ecosystem more effectively.
Molecular identification and habitat requirements of the hybrid Ranunculus circinatus × R. fluitans and its parental taxa R. circinatus and R. fluitans in running waters
AbstractRanunculus species grouped in the section Batrachium (water crowfoots) indicate the most valuable fluvial habitat in Europe under the EU Habitats Directive, and recognition of their environmental preferences plays a crucial role in efficient conservation. Moreover, water crowfoots are used in various monitoring systems throughout Europe. The aim of this study was to identify the distribution patterns of two common water crowfoot species (Ranunculus fluitans, R. circinatus) and their hybrid (R. circinatus × R. fluitans) in relation to environmental variables in rivers. Various chemical and hydromorphological parameters were estimated for 54 river sites where 58 different Batrachium populations were recorded. Our study revealed the most distinct positive reaction of R. fluitans to rhithral conditions characterized by rapid currents and coarse substrate. R. circinatus × R. fluitans preferred larger channels, although this taxon also flourished in rhithral rivers. The preferences of R. circinatus were not so evident confirming its occurrence under a wide range of habitat conditions. The ecological reaction of the hybrid was compared with its parental species, revealing their ecological specificity, which is useful in designing appropriate conservation programmes.