Cyanotoxins in the Italian Deep Subalpine Lakes (DSL): distribution and controlling factors

Toxic cyanobacteria blooms represent a serious threat for many aquatic ecosystems worldwide. The most common potentially toxic cyanobacteria in temperate waters belong to the genera Microcystis, Planktothrix, and Dolichospermum, which have the ability of producing microcystins and anatoxins. Toxins can produce severe effects on humans directly (contact or ingestion of contaminated water) or indirectly (consumption of contaminated food). Deep Subalpine lakes Garda, Iseo, Como, Maggiore, and Lugano are important water resources in the Italian Northern district. We have conducted a sampling campaign in these lakes with the aim of compare the cyanotoxin diversity. We have applied advanced analytical techniques based on LC-MS/MS technologies. Two main classes of toxins have been found: microcystins (MCs) and anatoxins. A big variability in MC variants and concentrations has been found among the lakes. In the largest lake (Garda) we have also investigated in detail the temporal dynamics of the toxin production. The concentration of total MCs was strictly linked to the temporal dynamics of Planktothrix rubescens in the lake, irrespective of the season and vertical depth. These findings suggest a constitutive MC production relatively independent from environmental factors. It is stressed how the estimation of models linking MCs and cyanobacteria abundances should provide a greater reliability in the definition of management strategies aimed at minimising the risks due to cyanobacteria development.