UNIVERSITY OF SASSARI Dissertation for the Degree of Doctor of Architecture and Environment presented at Sassari University in 2019 XXXI Cycle Ecological surveys for the valorization of spring environments of Sardinia: implications for their fruition and environmental protection. PH.D. CANDIDATE: Giuseppina Grazia Lai DIRECTOR OF THE SCHOOL: Prof. Vincenzo Pascucci TUTOR: Dr. Bachisio Mario Padedda CO-TUTOR: Prof. ssa Antonella Lugliè SUPERVISORS: Prof. Marco Cantonati Prof. Luc Ector Dr. Carlos Eduardo Wetzel My faith is in you, Father almighty, Creator of heaven and earth, of the visible and invisible universe To my parents and to my dear friend Bruno Index Abstract [in English and Italian] 3 1. Introduction 5 2. Diatoms 15 3. Objectives and contents 24 4. Material and methods 26 5. Chapter I Mediterranean karst springs: Diatom biodiversity hotspots under the pressure of climate change and nutrient enrichment 31 6. Chapter II Diversity, ecology and distribution of benthic diatoms in thermo-mineral springs of Auvergne (France) and Sardinia (Italy) 62 7. Chapter III Chamaepinnularia thermophila (Bacillariophyceae): synonymy with Navicula tongatensis Hustedt and update of its geographic distribution and ecology 95 8. Chapter IV Sellaphora gologonica sp. nov. (Bacillariophyta, Sellaphoraceae), a new diatom species from a Mediterranean karst spring (Sardinia, Italy) 117 9. Chapter V Periphytic diatoms of the Mediterranean karst spring Sa Vena (Su Gologone system, Sardinia, Italy): relationships with environmental variables and effects of an extreme flash flood 131 Giuseppina Grazia Lai, Ecological surveys for the valorization of spring environments of Sardinia: implications for their fruition and environmental protection. PhD Thesis in Architecture and Environment, XXXI Cycle, University of Sassari. 1 10. Chapter VI Diatom assemblages from different substrates of the Casteldoria thermo-mineral spring (Northern Sardinia, Italy) 148 11. Chapter VII Epilithic diatom assemblages and environmental quality of the Su Gologone karst spring (central-eastern Sardinia, Italy) 168 12. General Conclusions 184 13. General References 187 Acknowledgements 212 Giuseppina Grazia Lai, Ecological surveys for the valorization of spring environments of Sardinia: implications for their fruition and environmental protection. PhD Thesis in Architecture and Environment, XXXI Cycle, University of Sassari. 2 Abstract Springs are ecosystems with unique features and great ecological value. In the Mediterranean area they are more exposed to the risks of alteration of their structure and natural functioning because of direct and indirect human pressures and climate change. Despite this, springs remain poorly studied and specific approaches of management and protection are still missing. The main purpose of this PhD was to acquire knowledge on ecology of karst and thermo-mineral springs of Sardinia, traditionally neglected. The research activities focused on diatom microflora from different substrates in 17 springs of the Island. The results indicated a high diatom biodiversity, also highlighted by the presence of Sellaphora gologonica sp. nov. and Chamaepinnularia thermophila, the latter observed only in very few sites in the world so far. The analysis of the relationships between species and environmental variables, confirmed that diatoms can reflect the effects of important factors related to the vulnerability of these ecosystems, such as hydrological stability (flow permanence), discharge, climate change (extreme flash floods) and nutrient enrichment. This thesis offer food for thought on the importance of enhancing and preserving these environments so important from an ecological point of view and of so large interests for human uses. The information collected may represent a starting point for the development of strategies aimed at their proper management. KEYWORDS : Mediterranean springs, karst springs, thermo-mineral springs, Bacillariophyceae, diatom biodiversity, species distribution, ecology, climate change. Giuseppina Grazia Lai, Ecological surveys for the valorization of spring environments of Sardinia: implications for their fruition and environmental protection. PhD Thesis in Architecture and Environment, XXXI Cycle, University of Sassari. 3 Riassunto Le sorgenti sono ecosistemi con caratteristiche uniche e grande valore ecologico. Le sorgenti dell’area Mediterranea sono maggiormente esposte a rischi di alterazione della loro struttura e del loro funzionamento naturale a causa di pressioni antropiche dirette e indirette e dei cambiamenti climatici. Nonostante questo, le sorgenti rimangono poco studiate e mancano ancora approcci specifici di gestione e tutela. Lo scopo principale di questo dottorato è stato quello di acquisire prime conoscenze sull’ecologia di sorgenti carsiche e termo-minerali della Sardegna. Le attività di ricerca hanno riguardato 17 sorgenti dell’Isola e lo studio è stato focalizzato sulla microflora delle diatomee di diversi substrati. I risultati ottenuti hanno indicato un’elevata biodiversità, evidenziata anche dalla presenza di Sellaphora gologonica sp. nov. e Chamaepinnularia thermophila, finora osservata solo in pochissimi altri siti del Pianeta. L’analisi delle relazioni tra specie e variabili ambientali ha confermato che le diatomee possono riflettere importanti fattori legati alla vulnerabilità di questi ecosistemi, come stabilità idrologica (permanenza del flusso), portata, cambiamenti climatici (eventi alluvionali estremi) e arricchimento di nutrienti. Questa tesi offre spunti di riflessione sull’importanza di valorizzare e preservare questi ambienti così importanti da un punto di vista ecologico e di vasto interesse per gli usi umani. Le informazioni raccolte possono rappresentare un punto di partenza per lo sviluppo di strategie finalizzate a una loro corretta gestione. PAROLE CHIAVE: sorgenti Mediterranee, sorgenti carsiche, sorgenti termo-minerali, Bacillariophyceae, biodiversità delle diatomee, distribuzione delle specie, ecologia, cambiamenti climatici. Giuseppina Grazia Lai, Ecological surveys for the valorization of spring environments of Sardinia: implications for their fruition and environmental protection. PhD Thesis in Architecture and Environment, XXXI Cycle, University of Sassari. 4 1. Introduction 1.1. Springs: definition and general characteristics Springs are freshwater ecosystems formed by the natural emergence of groundwater (Bohle 1995, Reiss & Chifflard 2015). They occur where the water table intersects with the earth’s surface or groundwater reach the surface through rock faults, fractures or depressions (Death et al. 2004, Scarsbrook et al. 2007). From the hydrogeological/bio- speleological point of view, springs are a main drainage point of a subterranean hydrographic system. Their physical and chemical characteristics (e.g., discharge, flow permanence, temperature and water chemistry) as well as the presence of some organisms linked to the groundwater, are relatively stable compared to other superficial water ecosystems (Gooch & Glazier 1991, van der Kamp 1995) and are mainly determined by the hydrogeological properties of the parent aquifer (van der Kamp 1995, Cantonati et al. 2006). For this reason, springs have been included among the “Groundwater Dependent Ecosystems” (GDEs) (Eamus & Froend 2006) in the category “obligately dependent” (Naiman et al. 2006, Kløve et al. 2011). From the hydrobiological point of view, springs are mainly the origin of running surface waters and can be integrated into the upper part of a stream system (headwater). In the longitudinal zonation of running waters, they occupy a specific zone namely crenal divided into two subzones: springhead (eucrenal) and springbrook (hypocrenal), characterized by differences in structural and environmental parameters and in species composition (Reiss & Chifflard 2015). The boundaries of these subzones are not easily definable because the changes occur gradually and vary depending on the variables (Scarsbrook et al. 2007). Springs are heterogeneous and very numerous environments on a global scale (Cantonati et al. 2012b, Glazier 2014). They have disjunct distributions and highly site-specific characteristics (Cantonati & Lange-Berlatot 2010, Cantonati et al. 2012b) and can be considered “island biotopes” o “water islands” (Werum 2001, Whittaker et al. 2001), capable of hosting specific and well differentiated biocoenoses (Cantonati et al. 2012b). From the ecological point of view, springs are 3-way ecotones that link ground and surface waters, spring and headwater stream, terrestrial and aquatic ecosystems in 4-dimensional framework: longitudinal, lateral, vertical, and temporal (Ward 1989, Scarsbrook et al. 2007, Cantonati et al. 2012b). Giuseppina Grazia Lai, Ecological surveys for the valorization of spring environments of Sardinia: implications for their fruition and environmental protection. PhD Thesis in Architecture and Environment, XXXI Cycle, University of Sassari. 5 As ecotones, they have specific abiotic and biotic properties and processes (energy and material flow) and ensure interactions and exchanges important for the structural (e.g. community structure, biodiversity) and functional attributes (e.g. nutrient dynamics) of adjacent ecosystems (Naiman & Decamps 1997, Ward & Tockner 2001, Ward & Wiens 2001). Despite their usually limited dimension, springs are complex ecosystems characterized by different aquatic, semi- aquatic and semi-terrestrial microhabitats (e.g. mosses and debris layers) that build mosaic-like