Arsenic (As) is one of the most toxic pollutants commonly associated with mine tailings and Acid MineDrainage (AMD), with concentration ranging from < 1 µg.L-1 to hundred mg.L-1 in mine water [1].Considering the toxicological effects of Arsenic on organisms, it is essential to develop remediationstrategies specifically dedicated to the treatment of As-rich AMD. In the former mine of Carnoules(Gard, France), AMD formation coincides with the creek of the Reigous stream. Natural attenuation ofAs occurs at this site via a coprecipitation with iron (III) [2,3]. This natural process, based on bacterialoxidation of iron and arsenic, represents a promising strategy for the development of biologicaltreatment of AMD. In this context, it is necessary to better understand the influence of biological andenvironmental parameters on the diversity and activity of iron and arsenic oxidizing bacterialpopulations involved in As and Fe removal.In the present work, we have hypothesized that the influence of environmental parameters (temperatureincrease and nutrient supply) will have a significant impact on the composition or activity of bacterialcommunities and consequently on the processes of iron and arsenic oxidation. To test this hypothesis,we conducted a batch experiment with AMD water collected at the Reigous spring. We have tested threebiotic conditions: (i) incubation at 35°C corresponding to optimal temperature for arsenic oxidizingbacteria, (ii) nutrient supply (0.2 g.L-1 of yeast extract) used for heterotrophic growth and (ii) controlconditions (20°C, which corresponded to summer field water temperature, without nutrient supplement).For each conditions tested, abiotic controls have been performed in parallel with filtered-sterilized DMAwater. Dissolved As and Fe concentrations in batchs were monitored during eight days. At the end ofthe experiment, the speciation of As (As(III)/As(V) ratio) was determined in the precipitates that formedin the batchs and the composition of bacterial community in water was characterized by high throughputsequencing of 16S rRNA ribosomal gene.No changes in soluble Fe and As concentrations were observed in the abiotic controls, confirming thekey role of microorganisms in arsenic and iron removal. At the end of the experiment, 100% of arsenicwas precipitated in the batchs heated at 35°C and in the batchs supplied with nutrients, whereas only68% of arsenic was precipitated in the control batchs. In contrast, iron precipitation was higher in thecontrol (96%) than in the 35°C and nutrient conditions (73% and 23%, respectively). Arsenic speciationin the precipitates also revealed differences, with higher proportion of As(V) when nutrients were added.These findings suggest that nutrient addition stimulated arsenic oxidation by heterotrophic bacteriawhereas iron oxidation, mainly due to autotrophic bacteria, was inhibited. To characterize themodifications induced in the bacterial community composition by the treatments (temperature andnutrients), 16S rRNA genes were sequenced using high throupthut approach and aioA gene wasquantified. In conclusion, our study opened new research perspectives for the development of abiological treatment process taking into account the influence of key parameters (temperature, nutrients)on the composition and activity of bacterial communities involved in iron and arsenic removal in AMD.