Sampling protocol to study benthic invertebrate community in a restored braided river

Braided rivers are characterised by a multichannel pattern maintained by a dynamic hydrologic regime with alternance of floods and low water periods. In this context, the aquatic habitat mosaic displays high turnover rates. Nevertheless, benthic invertebrate communities present in these systems are adapted to these dynamic conditions and have recently shown a high diversity due to the spatial pattern of habitats mosaic. In Europe, benthic invertebrates are used to evaluate and monitor the effects of hydromorphological restoration on the ecological status (sensu WFD), but to date, there is not any protocol adapted to the specificities of braided rivers. The question is then : does hydromophological restoration allow to recover a diverse spatial pattern in the benthic invertebrate community ? This work is based on the study of two reaches located on the Drac river (France), where one was restored in 2014 and the other displays a functional braided morphology. A new sampling methodology based on the national protocol (IBG-DCE) has been tested and relies on the identification of different types of channels and hydromorphological units. Three samples are taken from each identified unit, selected to represent the diversity of the braided reach, in the limit of 10 units. First results show a spatial pattern in the repartition of the community, especially between channel types. These results show the importance to consider the spatial morphological pattern of braided rivers in the sampling distribution. This study allowed us to better understand the structure and functioning of benthic invertebrate community within braided rivers