Knowledge, prediction and management of toxic Cyanobacteria blooms in the Sardinian man-made lakes (western Mediterranean).

The affirmation of toxic Cyanobacteria is considered the worst and most frequent typology of Harmful Algal Blooms (HABs) in freshwater environments, with serious consequences also for human health. In this scenario the development of useful tools in the early prediction of toxic Cyanobacteria blooms is considered very important, as well any indication to better manage these events. With this main objective, since 2010, a research project, financed by Autonomous Region of Sardinia (L.R. 7/2007), has been carried out on four man-made lakes (lakes Bidighinzu, Monte Lerno, Sos Canales and Torrei) of Sardinia (Italy) whose waters are used for drinking and characterized by different trophic state. The presence of potentially toxic species was observed: for some of them it was a confirm (i.e., Planktothrix agardhii-rubescens group), whereas for others, this was the first report (i.e., Anabaena Viguieri (Denis & Fremy) and Aphanizomenon klebahnii (Elenkin) Pechar et Kalina) also for the Mediterranean area. A. Viguieri and Aph. klebahnii are listed as toxic (microcystins). The highest cellular densities of Cyanobacteria were observed in Monte Lerno Lake in October 2010 (278 x 106 cell. l-1) and in Bidighinzu Lake in August 2010 (896 x 106 cell. l-1). Also the major toxin peaks, were relieved in these two lakes and were, respectively, of 4.49 ppb in Monte Lerno Lake in April 2011 and 2.30 ppb in Bidighinzu Lake in October 2011. nMDS highlighted significant differences among the lakes as regards the abundances of toxic Cyanobacteria and no-toxic Cyanobacteria. Further, Pearsons correlation indicated a strong relationship between trophic status (Bidighinzu and Monte Lerno are the most eutrophic among the four investigated reservoirs) and presence of toxic Cyanobacteria.