Cyanotoxin detection in freshwater systems from the North and Center of Portugal

In recent years, freshwater ecosystems have undergone changes in their physical, chemical and biological properties due to eutrophication processes. The increase of nutritive compounds in the water leads to an accelerated growth of all aquatic productivity, especially in the cyanobacteria communities. The densification of the cyanobacteria community in the water surface leads to the production of cyanotoxins, secondary metabolites that contribute to the degradation of the water quality and has serious consequences for both the environment, animal and human health. With a high variety of chemical variants and several degrees of toxicity, cyanotoxins can be grouped according to their mode of action in hepatotoxins (microcystins, nodularins), cytotoxins (cylindrospermopsin), neurotoxins (anatoxin-a, saxitoxin) and dermatotoxins (lyngbyatoxin, aplysiatoxin). The aim of this study is to detect the presence of microcystins, cylindrospermopsin, anatoxin-a and saxitoxin in freshwater systems from the North and Center of Portugal, through chemical, biochemical and molecular methods. To achieve such goal, environmental samples from seven freshwater systems from the North and Center of Portugal were analyzed for the presence of amplified fragments of genes involved in cyanotoxin biosynthesis (molecular methods) and, when those fragments were present, samples were quantified in order to detect and quantify toxins, through chemical and biochemical methods. The results showed the presence of microcystins, cylindrospermopsin, anatoxin-a and saxitoxin in the studied freshwater systems and the potential for their production by the cyanobacteria genera present in the water environment. Also the efficiency of the molecular methods in monitoring programs to detect the presence of cyanotoxins and their producing cyanobacteria genera revealed to be an effective and valuable tool. In the absence of other information about the presence of anatoxin-a, cylindrospermopsin and saxitoxin in Portuguese freshwater systems, this study constitutes the first report of the presence of these cyanotoxins in Portuguese freshwater systems.