Molecular characterization of harmful algal species

The main purpose of the research activities carried out in this thesis was to give contributions to ecological studies on potentially harmful algal species (HAS) present in Sardinia’s aquatic environments through the application of biomolecular techniques. In Sardinia, as well as globally in the world, the reports of blooms caused by HAS (Harmful Algal Blooms, HABs) have increased in recent decades, requiring specific studies and investigations.The identification of the species involved is particularly important. Microalgae species identification based on cell morphology with the traditional microscopic methods is not a simple task. A valid support is represented by the recently developed biomolecular tecniques which can help in resolving species identification and detection problems.In this thesis, several cases of study were investigated, regarding different types of environments, algal classes, genera, species within a same class and, therefore, different linked problems. Analyses were carried out on natural samples fresh or fixed and cell cultures obtained from isolated vegetative cells and/or cysts of resistance. The identification of HAS was carried out using molecular techniques, with nucleotide sequences of the LSU (or 28S rDNA) and 5.8S rDNA-ITS (internal transcribed spacer) regions such as genetic markers.The confirm of taxonomic attribution was achieved for new isolates of theAlexandriumHalim genus, analysing cell cultures obtained by the germination of cysts isolated from sediments and the growth of vegetative cells isolated from the water column from different areas of Sardinia (Chapter Ia, Ib).The presence ofChattonella subsalsaBiecheler was assessed in samples collected from the Santa Giusta Lagoon during events of fish kills in the summers of 1994, 1998, 1999 and 2010 by analyzing samples fixed with Lugol and conserved in the Department's collection (Chapter II).It was possible obtain a preliminary framework of the HAS’s presence in beach environments, includingAlexandrium tayloriiBalech,Ostreopsiscf.ovataFukuyo,Barrufeta bravensisSampedro et Fraga andGymnodinium instriatumFreudenthal et Lee (Chapter III).Finally, the first study on dinoflagellates species involved in blooms in reservoirs of Sardinia, was carried out (Chapter IV).