Diatom Diversity in the Surface Waters of Oued Beht

Diatoms, known for their rapid response to environmental changes, are widely recognized as reliable bioindicators of water quality. Despite their ecological significance, studies on diatom flora in North Africa, particularly in Morocco, remain scarce. This study evaluates the water quality of Oued Beht in northwestern Morocco by integrating physico-chemical analyses with diatom community assessments.Sampling conducted in March 2024 at a representative site revealed elevated pH (9.63), high conductivity (9690 µS/cm), and increased salinity (5.3 mg/L), indicative of significant anthropogenic pressures from domestic, agricultural, and industrial discharges. In contrast, diatom community composition, dominated by pollution-tolerant taxa such as Navicula radiosa (represented by 15 taxa), yielded a diatom biological index (IBD) of 15.76, suggesting relatively good historical water quality.This apparent discrepancy underscores the resilience and ecological memory of diatom communities, which may reflect past conditions even as current physico-chemical parameters indicate moderate environmental degradation. These findings highlight the importance of adopting a holistic approach to monitoring aquatic ecosystem health in Morocco, combining biological and physico-chemical indicators to better understand and manage anthropogenic impacts.