ALGAL CYANOTOXIN PRESENCE IN LAKE USED FOR DRINKING WATER PRODUCTION AND IRRIGATION IN THE SOUTH OF ITALY

The problem of the growth of cyanobacteria in the water resources used for drinking water production or for irrigation is an emerging problem for the management of these resources. In lakes around the world and even in fresh water reservoirs, the number of cases of algal blooms due to cyanobacteria has increased in recent years. The development of these abundant blooms has become a serious environmental problem, since many species are able to produce cyanotoxins, as secondary metabolites, that are highly toxic to humans and aquatic organisms. Microcystins, highly toxic cyclic peptides, are a group of hepatotoxins produced by a large number of aquatic species of cyanobacteria, such as Microcystis, Anabaena and Planktothrix. A massive development of Planktothrix rubescens was observed in 2009 in a reservoir (Lake Occhito) used for crop irrigation and drinking water production in Southern Italy (Apulia Region). A one-year sampling campaign on the lake assessed the dynamics of phytoplankton cyanobacteria and the temporal evolution of toxin production. The endo-cellular microcystins were separated from extracellular content by filtration and extraction. The values of endo-cellular microcystins were compared to those of algal density and chlorophyll-a content. The microcystin detected was [D-Asp3] microcystin-RR, identified by retention time and spectrum comparing with a certified standard. Microcystin extra-cellular concentration were never above the WHO limits for drinking water use (1 µg/L) and the maximum level of dissolved microcystin was 0.7 µg/L on April 2009 sample while highest endo-cellular concentration (30.8 µg/L) of [D-Asp3] microcystin-RR was measured. As predictable, endo-cellular toxin was 92-97% of the total microcystin content; the endo-cellular content ranged from 10 to 40 times greater that the dissolved content.