Cyanotoxins in Lake Garda? The critical evaluation of chemodiversity

Anthropic pressure and climate changes are the major stressors in lakes. Both factors play an important role in the development of cyanobacteria with the capability of producing toxic metabolites (cyanotoxins). Cyanotoxins have negative effects on aquatic flora and fauna, and can be cause of serious intoxications episodes in animals and humans. Some cyanotoxins moreover can undergo bioaccumulation. Lake Garda hosts some potentially toxic cyanobacteria (Planktothrix rubescens and Dolichospermum lemmermannii) which are known to produce microcystins (hepatotoxins) and anatoxins (neurotoxins). The European Community funded the EULAKES project, which supported a monitoring campaign in 2010-2012 aimed at assessing the presence of cyanotoxins in Lake Garda. In that period the chemical diversity and the abundance of cyanotoxins were investigated by advanced analytical techniques (LC-MS) with a monthly frequency. The survey showed that some cyanotoxins (in particular microcystin RRdm) were present in the lake water with concentrations, however, which did not represent a sanitary risk. The most abundant toxins were microcystins, which five variants have been identified, and anatoxin-a. The highest content of toxins has been registered in spring-summer periods. The data collected, in combination with biological and environmental parameters, provide useful indications for a rational management of possible toxic bloom