Diversification of macrophytes within aquatic nature-based solutions (NBS) developing under urban environmental conditions across European cities

Abstract

This article explores the diversification of macrophytes in aquatic nature-based solutions (NBS) under urban conditions across European cities, highlighting their role in enhancing climate resilience, biodiversity, and ecosystem quality. While aquatic NBS have been studied for engineering and social aspects, comprehensive biological analyses, particularly across geographical gradients, have been lacking. This research, part of the BiNatUr project, investigates macrophyte richness in aquatic NBS in five European cities: Belgium, Finland, Germany, Poland, and Portugal. The study involved 120 sites, with each city contributing 12 sites representing restored or constructed ponds and streams in both altered and natural states. Surveys conducted used 10-meter quadrats to assess the abundance of macrophytes, which were identified to species level. The analysis included emergent, submerged, and floating plants, using Ellenberg indicator values (EIV) for ecological preferences related to light, temperature, continentality, moisture, pH, and nutrient levels. A total of 103 aquatic plant species were identified, with significant variability in species richness and abundance among the cities. Helsinki had the highest species richness, averaging 7.25 species per site, while Berlin had the lowest at 3.54 species per site. Macrophyte abundance was highest in Finland and Poland, with 44.8% and 35.7% coverage, respectively, and lowest in Germany at 12.2%. Detrended Correspondence Analysis (DCA) highlighted significant differences in macrophyte community structures, with Lisbon showing a unique species composition. The study underscores the diversity of macrophytes in urban aquatic NBS across Europe, emphasizing their value as biodiversity hotspots in urban settings. These findings provide crucial insights into macrophyte abundance, species richness, and ecological characteristics, contributing to the understanding of aquatic ecosystems under high stress in cities and informing conservation and urban planning initiatives.