Cyanobacteria, B-N-methylamino-L-alanine and microcystins in eutrophic Mediterranean reservoirs: the case study of Lake Bidighinzu (Sardinia, Italy).

In Sardinia, water for drinking derives primarily from reservoirs, the majority of which is eutrophic. Cyanobacteria are the dominant group in the phytoplankton, especially in the summer-autumn period, the most critical seasons for the quality and the uses of water. Recently, a relationship between the trophic state, cyanobacteria abundance and microcystins (MCs), the most frequent cyanotoxins recognised worldwide, was assessed for Sardinian reservoirs. Sardinia represents also a genetic isolate, characterized by a higher frequency than expected of the rate of Amyotrophic Lateral Sclerosis and of genetic mutations involved in different neuropathological conditions. β-N-methylamino-L-alanine (BMAA) production is a potent not yet well investigated neurotoxin, produced by Cyanobacteria, involved in the Amyotrophic Lateral Sclerosis/Parkinsonism dementia complex. This study investigated on the relationships among environmental variables (14), Cyanobacteria, and BMAA and MCs in a hypereutrophic reservoir, Lake Bidighinzu (North-Western Sardinia, Italy) whose waters are mainly used for drinking. Enzyme Linked Immunosorbent Assay (ELISA) for determination of BMAA and MCs were used in surface and subsurface water, collected weekly from March to October 2014. BMAA and MCs positives were found in almost all the samples (n = 22). MCs > 1 μg l–1, the World Health Organization limit for MCs in drinking water, was registered in correspondence of Cyanocatena sp. bloom (about 5 * 108 cells l-1) in September and in October. BMAA maximum was found in correspondence of Dolichospermum flos-aquae bloom (> 6 * 107 cells l-1) in June. A redundancy analysis separated the cyanotoxins and relative toxic species of Cyanobacteria into two main groups: Dolichospermum species (related to BMAA and most important nutrients), and Microcystis species (related to MCs and DO). Our results offer a first estimation of concentrations of BMAA and a further report on MCs and relationship with Cyanobacteria assemblages and trophic state of Bidighinzu Lake.