A Decade of Macrophyte-Based Ecological Monitoring in Rivers and Streams of Greece – Assessing changes in ecological quality and temporal community shifts

Konstantinos Stefanidis^1*Georgios Dimitrellos^1,2Dionysios Tsoukalas¹EVA SOCRATES PAPASTERGIADOU¹

• ¹Department of Biology, School of Science, University of Patras, Patra, Greece
• ²Panepistemio Patron, Patras, Greece

Aquatic macrophytes are one of the four Biological Quality Elements (BQE) that EU Member States are required to monitor under the Water Framework Directive (WFD 2000/60). In this context, a systematic macrophyte monitoring survey has taken place across more than two hundred lotic ecosystems of Greece for over a decade. This study analyzes long-term ecological assessments using macrophyte species to detect temporal changes in ecological quality and macrophyte communities. Presence–absence data from 137 sites that were sampled at least twice, were used to explore temporal changes in alpha and beta diversity. Ecological quality classifications were analyzed in relation to macrophyte diversity changes to determine whether improvements or deteriorations in ecological quality are reflected in species richness and community composition. Temporal beta diversity and local contribution to beta diversity were calculated to identify shifts in community composition. Our findings indicate that ecological quality has remained largely unchanged, with limited signs of improvement. However, macrophyte assemblages have undergone notable shifts in composition, reflecting the impact of significant anthropogenic interventions. These findings highlight the importance of long-term monitoring for detecting ecological shifts driven by cumulative environmental change that shorter-term assessments may miss and emphasize temporal beta diversity as a useful tool for revealing such dynamics.