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).