Improvement of the knowledge of diatom ecology by coupling geochemistry, radioactivity and taxa inventory in thermo-mineral springs of a volcanic and upland area in south-central France, the Massif Central

Abstract

ABSTRACT In connection with its geological history, many thermo-mineral springs are present in the Massif Central (France). The physicochemical characteristics of these springs (temperature, mineralization, gas content) result both from their deep circulation and from the geological formations or surface waters with which they interact during their ascent. In mineral springs, diatoms are well represented. To date, no study has focused on coupling the origin of water with diatom communities, whether in the Massif Central or in other parts of the world. The purpose of this study is to cross the information obtained on the water and the diatoms in order to analyse the biodiversity and improve knowledge of the species autecology. Twelve mineral springs with some of which have high levels of radioactivity were studied in the Massif Central. As results, the geochemical facies, the origin of the water and the Total Dissolved Solids influence the taxonomic composition but not the specific richness, Shannon index and Evenness. Furthermore, 222Rn influences diatom richness and community structure. Planothidium frequentissimum, Crenotia angustior and Sellaphora labernardierei were associated with high values of 222Rn activity. The water temperature was a factor that influences diatom species distribution. Some species appears to be more sensitive to the composition of water, such as Planothidium frequentissimum which attests to a mixing between deep and surface waters.