Freshwater ecosystems are vital for biodiversity and human well-being, but remain amongst the most degraded globally. Nature-based Solutions (NbS) offer a promising pathway to restoration, yet implementation remains fragmented and often limited in scale. This paper synthesises insights from 18 demonstration cases across Europe, carried out under the EU Horizon 2020 MERLIN project, to identify key factors enabling the systemic upscaling of freshwater restoration through NbS. Drawing on practical experiences, five interdependent “building blocks” are proposed: (1) comprehensive status review; (2) narratives of the future; (3) evidence-informed approach; (4) resource management and (5) stakeholder engagement. These dimensions reflect cross-cutting challenges and capacities — such as context-sensitive planning, adaptive learning, financing strategies and inclusive governance. While grounded in diverse local contexts, the framework offers a strategic orientation for scientists, practitioners and policy-makers working to align restoration efforts with the ambitions of the European Green Deal and Nature Restoration Regulation. Rather than prescribing uniform solutions, the paper provides practice-informed guidance for embedding restoration in complex social–ecological systems. Highlights Synthesises lessons from 18 diverse freshwater restoration cases across Europe under the MERLIN project;Proposes five strategic building blocks for scaling Nature-based Solutions: system understanding, shared vision, evidence use, resource management and stakeholder engagement;Emphasises the interdependence of ecological, institutional and societal dimensions in upscaling restoration;Demonstrates the value of transdisciplinary collaboration, adaptive planning and embedded implementation;Offers practice-orientated insights aligned with the European Green Deal and Nature Restoration Regulation.
Floodplain habitat area and quality have decreased significantly over the last decades, mainly due to anthropogenic changes. Conservation efforts targeting floodplain species must consider changing climate when choosing suitable areas for restoration, especially for sessile organisms. Species distribution models, based on data from national and international databases on species’ occurrences and various environmental predictors, allow forecasting changes in species’ spatial distributions and facilitate planning at the catchment scale. Modelled predictions for floodplain organisms and communities suggest that current protected floodplains in Switzerland do not provide sufficient habitat and refugia for typical floodplain species and that climate-adapted conservation planning is needed which includes new areas. Similarly, visualisations of habitat which might potentially be occupied in the future can help to distinguish refugia from short-term sanctuaries. Temporal changes in water availability, for example, during periods of droughts, are likely to further lead to local habitat decrease of floodplain plant communities, as can be shown in hydrological models at reach scale for the Rhine in Germany. In fragmented landscapes along rivers, protected areas can provide refuge for specialised terrestrial species and promote species conservation, as we report for a floodplain which was protected for 30 years. Future restoration projects at the reach scale should, therefore, include planning at the catchment level, as well as consider hydrological regimes at the reach scale, especially for sessile floodplain species’ conservation under changing climate. Highlights Floodplain communities are threatened, especially sessile species; Climate-driven species distribution models distinguish refugia and sanctuaries; Hydrological predictions under changing climate show shifts of habitat for riverine plants at the local scale; A case study from a protected area shows that it promotes floodplain biodiversity; Prioritisation of local restoration projects should be based on planning at the catchment scale.
Comparative proteomic analyses including ecologically distinct sulfate-reducing strains and different cellular fractions are scarce, limiting our understanding of corrosion-related mechanisms under anoxic conditions and the identification of protein signatures relevant to microbiologically influenced corrosion (MIC). To capture both freshwater and marine adaptations, we investigated the well-established SRB model strains Desulfovibrio vulgaris and Desulfovibrio ferrophilus. We compared energy metabolism, electron transport pathways, and growth patterns in both strains cultivated with lactate, H2, or steel as electron donor. Time-dependent biophysicochemical measurements, SEM/EDX, and shotgun proteomics were performed. We explored cellular proteins in planktonic and biofilm fractions, as well as potential extracellular enzymes in the supernatant. In both the strains, growth with steel revealed energy metabolisms more similar to H2-dependent metabolism instead of direct iron-to-microbe electron transfer (DIMET). Increased abundances of periplasmic hydrogenases and c-type cytochromes served as proteomic signatures supporting H2-mediated iron-to-microbe electron transfer (HIMET). Concomitant to bacterial growth and biofilm formation, mineral deposits of carbonates, phosphates and FeS were formed, the latter especially in saltwater treatments. The close association of D. ferrophilus cells with FeS particles supports the possibility of the role of FeS in electron transfer in addition to H2 as well as formate mediated electron transfer which may have contributed to the high corrosion levels with D. ferrophilus. Neither strain exhibited increased abundances of redox proteins known to be involved in extracellular electron transfer, supporting that DIMET may have not been a dominant mechanism under the given conditions. This interpretation is also in line with the observation that only a small proportion of the total cells were associated with the steel surface, and that direct cell-to-steel contact was not observed. These findings show that SRB can be metabolically flexible and that hydrogenase-based systems are sufficient for steel-dependent growth leading to corrosion. This is especially relevant in natural environments, where more than one type of electron donor is available and different modes of extracellular electron transfer exist.
Water-filled rubber gates are increasingly being installed in rivers and canals as variable barriers for the regulation of water levels. The synthetic cylindrical membranes are in direct and continuous contact with the water body and especially after prolonged water retention inside the enclosed membrane, leached rubber additives may accumulate and enter the river in increased quantities. This study provides the first comprehensive and systematic investigation of material emissions from membranes used for inflatable rubber gates. For this purpose, materials of three different authentic rubber gate membranes were characterized and subjected to leaching in deionized water for subsequent ecotoxicological and chemical analyses. Leachates from all three materials caused significant acute toxic effects on algae, daphnia and luminescent bacteria. Furthermore, two membranes released chemicals causing estrogenic and anti-androgenic effects, one of which also induced aryl hydrocarbon receptor-mediated effects. In parallel, phenanthrene, pyrene, naphthalene, bisphenol A and 4-hydroxydiphenylamine (4HDPA) were detected in several samples by chemical analyses. Zinc was also released in elevated quantities from all tested materials. While 4HDPA and zinc significantly contributed to the estrogenic and acute toxic effects, respectively, the overall ecotoxicological effects could not be fully explained by the selected target compounds. The results of the laboratory experiments and the environmental relevance of materials were confirmed by the field sampling conducted. In total, the comparative assessment presented in this study can support the selection of environmentally compatible membrane materials and provides a basis for improving formulations of rubber materials.
Der Wasserkörper des Nord-Ostsee-Kanals (NOK) verbindet die Kieler Förde mit der Unterelbe und durchquert dabei drei hydrogeologische Räume: das östliche Hügelland, die Geest und die Marsch. In der Geest besteht zumeist unmittelbarer hydraulischer Kontakt zwischen dem NOK und dem Grundwasser in der Umgebung, in den anderen beiden Räumen nicht, das ergab eine bohrungsbezogene Analyse der hydrogeologischen Lagerungsbedingungen. Die hohen und über den Konzentrationen im Grundwasser liegenden Salzgehalte im Osten (> 10 PSU) nehmen mit zunehmender Fließstrecke des NOK nach Westen ab und sind in der Marsch bereits nahezu ausgeglichen bzw. unterschreiten (< 5 PSU) oftmals sogar die dortigen Konzentrationen im oberflächennahen, durch Nordseeeinfluss versalzenen Grundwasser. Es konnten Daten zu über 1000 behördlichen und von Dritten betriebenen Grundwassermessstellen analysiert werden, für die ein mehrstufiger Selektionsalgorithmus zur Identifizierung einer wahrscheinlichen salinaren Beeinflussung durch den NOK entwickelt wurde. Bei 40 kanalnahen Messstellen im Einzugsgebiet des NOK mit einer Entfernung von weniger als 3 km zum Kanal können – im Hügelland und der Geest temporär, in der Marsch lokal auch dauerhaft – influente Verhältnisse bestehen. Hier erfolgt ein Stoffeintrag in das Grundwasser, da die hydraulischen Potenziale des Grundwassers zeitweise oder dauerhaft tiefer als diejenigen des NOK liegen. Im Hügelland wurde nur bei zwei Messstellen ein durch den baulichen Ausbau der Oststrecke verursachter salinarer Stoffeintrag identifiziert; dieser zeigt jedoch klar das Gefährdungspotenzial, das vom NOK für das Grundwasser ausgehen kann. In der Marsch zeigen Landesmessstellen des Landesamtes für Umwelt Schleswig-Holstein (LfU SH) geogen erhöhte Salzkonzentrationen im Grundwasser, die nicht durch den NOK bedingt sind und auch über den Konzentrationen im Kanal liegen.
