At the request of the Tamagor Association, Fyto conducted a survey of aquatic plants in Lac Noir in July 2026. The study identified 63 aquatic plant beds covering 12% of the lake’s surface area, as well as 21 species or groups of aquatic plants. Overall, the lake supports diverse and relatively balanced aquatic vegetation, reflecting a healthy ecosystem. However, two invasive alien species were identified: Eurasian watermilfoil, found in 31 plant beds covering 6,588 m² (3.9% of the lake), and European frog-bit, observed in a single small colony. Although Eurasian watermilfoil is already distributed around the lake, its density remains generally low, providing a valuable opportunity to intervene before it spreads further.
The report recommends prompt and targeted action to limit the spread of these two invasive species and preserve the lake’s biodiversity. For Eurasian watermilfoil, approximately 2,892 m² of plant beds may require treatment, combining the installation of benthic barriers over the densest colonies with manual removal of isolated plants and less dense patches. As for European frog-bit, manual removal is recommended as early as 2027, while its presence remains very limited. Regular monitoring in subsequent years will be essential to prevent further spread.
The study emphasizes that taking action now could help protect the ecological balance of Lac Noir while reducing the costs and scope of future interventions.
The detailed results of the study are available here (French).