Cyanotoxins and their impact on water quality in Central Europe lakes

Cyanobacteria have a fundamental role in aquatic ecosystems. However, the presence of toxic species can pose serious health risks for humans and animals, besides having negative impact on all water uses. Some cyanobacteria genera have the potential of producing toxic secondary metabolites: hepatotoxins (microcystins, nodularins), neurotoxins (saxitoxins, anatoxins, BMAA), cytotoxins (cylindrospermopsins). Many countries have introduced legislative measures for controlling and limiting human exposure to these toxic compounds. The EULAKES project is a cooperation project involving four countries (Italy, Austria, Hungary and Poland) which has, among others, the ultimate goal of develop a common approach to tackle cyanobacterial threats based on scientific basis. We have chosen Lake Garda as model system in which we carry on scientific work aimed at analyzing the ecology of toxic cyanobacteria with special focus on the temporal dynamics of toxins production. Planktrothrix rubescens and Anabaena lemmermannii are the most frequent potential toxic species in this water basin. Since April 2010, Lake Garda was regularly investigated by monthly sampling. Cyanobacteria were identified and quantified; parallel to that, molecular diversity of toxins were also analyzed by using state of the art Liquid Chromatography/Mass spectrometry techniques. Mycrocystins (MCs) were mostly represented by desmethylated microcystin-RR (more than 90% of the total), which have a toxicity level of ca. 4 times lower than the most toxic microcystin (MC-LR, 50 µg kg-1 b.w.). Anyway, total microcystin concentrations never exceeded the WHO proposed limit of 1 µg/liter. In the considered period, the highest concentrations of MCs were found in the summer months, coinciding with the metalimetic development of Planktothrix populations. The results obtained in this project will give the opportunity to contribute to homogenise the procedures for risk evaluation and implementation of management strategies in the participating countries.