Diversity, ecology and distribution of benthic diatoms in thermo-mineral springs in Auvergne (France) and Sardinia (Italy).

Giuseppina G Lai,Luc Ector,Carlos E Wetzel,Antonella Lugliè,Bachisio M Padedda,Aude Beauger,Olivier Voldoire,Elisabeth Allain

doi:10.7717/peerj.7238

Abstract

This study investigated and compared the diatom flora from thermo-mineral springs in Auvergne (France) and Sardinia (Italy). Samples were collected from rock/cobbles and fine sediments in 16 springs between January 2015 and March 2017. A total of 207 taxa (59 genera) were found. Multivariate analyses revealed significant differences in species composition and abundance among diatom assemblages both within each geographic region and between Auvergne and Sardinia (global R = 0.516; p = 0.002), suggesting the importance of local and climatic factors in species distribution. Based on abundance and common occurrence in multiple sites, some taxa can be considered more representative of springs in each region: Crenotia thermalis for Auvergne and Lemnicola exigua, Nitzschia amphibia, N. inconspicua and Rhopalodia operculata for Sardinia. pH, conductivity and HCO3− were the most significant environmental variables for diatom assemblages. Our results highlight the high heterogeneity of these spring systems. Future taxonomic insights can be useful to define the identity of some abundant and dominant taxa not identified at the species level in this study. Their identification is a crucial step for a more precise ecological characterization and comparison of these peculiar spring systems.

Highlights

Thermo-mineral springs are a diverse group of aquatic environments with characteristics that make them very good prospects for different uses including industrial processing, bottled water, power generation, and in the health and well-being sector
The highest temperature values were observed at LEFO (32.6 ◦C) and CHAT (27.3 ◦C) in Auvergne, and at CAD1 (49.3 ◦C), CAD2 (53 ◦C) and CAS (71.5 ◦C) in Sardinia. pH ranged from slightly acid to alkaline with the minimum and maximum values at FDBL (6.42) and POIX1 (8.25) in Auvergne, and at ABB (6.32) and SBM (9.33) in Sardinia, respectively
Significant differences were found among diatom assemblages both within each geographic region and between Auvergne and Sardinia, according to our initial hypothesis

Summary

Introduction

Thermo-mineral springs are a diverse group of aquatic environments with characteristics that make them very good prospects for different uses including industrial processing, bottled water, power generation, and in the health and well-being sector. In Europe, investigations on diatom flora in thermo-mineral springs have been carried out in the Czech Republic (Bílý, 1934; Lederer et al, 1998; Kaštovský & Komárek, 2001), France (Beauger et al, 2015; Beauger et al, 2016; Beauger et al, 2017), Iceland (Schwabe, 1933; Schwabe, 1936; Krasske, 1938; Van der Werff, 1941; Biebl & Kusel-Fetzmann, 1966; Owen, Renaut & Jones, 2008), Italy (Dell’Uomo, 1986; Mannino, 2007; Lai et al, 2019), the Republic of Macedonia (Stavreva-Veselinovska & Todorovska, 2010), Slovakia (Hindák & Hindáková, 2006; Hindák & Hindáková, 2007), and Spain (Leira, Meijide-Failde & Torres, 2017) Overall, these studies were limited and focused on individual or multiple springs in specific geological settings and the comparison between different geographic areas is rare (e.g., Petersen, 1946; Owen, Renaut & Jones, 2008)

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