Knowledge, possibility of prediction and management of potentially 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 (H ABs) in freshwater environments, with serious consequences also for human health. For this, the development of useful tools in the early prediction of toxic Cyanobacteria blooms is considered very important. With this main objective, a research project, financed by Regione Autonoma della Sardegna (L.R. 7/2007), is carried out on four reservoirs in northern Sardinia since 2010: Bidighinzu, Monte Lerno, Sos Canales and Torrei, already investigated for many years, characterized by different trophic status and whose waters are used for drinking. The study includes the assessment of trends on an annual cycle of chemical and physical variables, nutrients and phytoplankton. Microcystin and nodularin concentrations are detected with the use of the Immunosorbent method ISS.BGA.044.REV00 (Reports ISTISAN 07/31). Preliminary results confirm the presence of potentially toxic species already found in these lakes, such as species of Planktothrix agardhii-rubescens group in the Monte Lerno Lake, and the new notification of species not yet reported in Sardinia, such as Anabaena macrospora (Klebahn), Anabena Viguieri (Denis & Fremy) and Aphanizomenon klebahnii (Elenkin) Pechar et Kalina in Bidighinzu Lake. Anabaena macrospora is not reported in the literature as potentially toxic, Anabaena Viguieri and Aphanizomenon klebahnii are listed as potentially harmful due to the production of microcystins. The highest cellular densities in Monte Lerno Lake in October (120 x 10^6 cell. l^-1) and in Bidighinzu Lake in September (293 x 10^6 cell. l^-1) corresponded to the major toxin peaks, respectively 3.92 ppb and 1.36 ppb. It is confirmed the relationship between trophic status (Bidighinzu and Monte Lerno are the most eutrophic among the four investigated reservoirs) and presence of toxic Cyanobacteria. Moreover the toxicity of Aphanizomenon klebahnii blooms represents a new information in the Sardinian and Mediterranean scenario.