Articles
Mitigating the impact of artificial water level fluctuations on reservoir biodiversity: the example of the UROS project and its floating islands
Received : 20 February 2026;
Published : 28 May 2026
References
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Abstract
Littoral zones of many water bodies, which are naturally very biogenic, are degraded by high water level fluctuations. The use of floating islands that provide diverse habitats on a permanent basis appears to be a potential compensation solution. In the UROS project, three islands have been designed and tested on the Serre-Ponçon reservoir. Their colonization by aquatic macrofauna was evaluated over four years.
A diverse and abundant community of macroinvertebrates was quickly observed on the islands compared to the control littoral zones and remained stable throughout the years. The taxa observed on the islands, typically less mobile and more sensitive to pollution, were different from those in the control areas subject to water level fluctuations. The fish community on the islands was less abundant, although overall not very different. In particular, juvenile stages were less numerous on the islands at night. However, a wide range of juvenile pike stages (target species of the project) was observed on the islands and not in the control areas, probably due to the complexity of the habitats offered by the islands. These encouraging results show that the floating islands partially restore the functionality of a littoral zone not impacted by high water level fluctuations. However, assessments need to be continued to confirm these trends over the longer term.
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