The clogging of stream beds:: A review of mechanisms and consequences on habitats and macroinvertebrate communities.

The clogging refers to deposition and infiltration of fine organic and inorganic sediments downward within the hyporheic zone. In this review, we presented clogging mechanisms and their spatio-temporal variability in the context of a global stream functioning. Clogging modifies stream bottom and interstitial habitats characteristics and reduces the exchange of water and dissolved substances between the stream surface and the hyporheic zone. Modifications of substrate structure, substrate stability, oxygen and trophic resources and predator influence lead to changes in community structure. In a first step, drift increases whereas the invertebrate abundance drops. In a second step, likelihood to survive, growing, standing crop and productivity are affected. Coarse substrate adapted assemblages are progressively replaced by invertebrates adapted to fine sediments. The studies about consequences of clogging on the hyporheos are scarce, but the major role of the hyporheos on the dynamic of streams suggests that its alteration would strongly decrease the stream resilience capacity after disturbances.