Cyanobacteria and Cyanotoxins in Sicilian Freshwater Basins (Italy): A Risk Assessment for Drinking Water

Abstract

The eutrophication of surface waterways led to a rise in harmful cyanobacterial blooms worldwide. Sicily, the biggest Italian region, suffers from a strong drought and a growing scarcity of clean water. Toxin producing Cyanobacteria (CB) in Sicilian dams have been often reported, but they have not been regularly monitored until today. Therefore, health risk associated with cyanotoxins (CTX) in drinking waters remains largely unknown. To prevent urban water crisis in next future, we need to manage all water resources effectively, especially the more dynamic surface freshwater sources. Aim of this study was to monitor the major dams of Sicily used as drinking water supplies to carry out a risk assessment relative to the presence of CB and CTX in raw waters.Seven out of thirty-three Sicilian dams, used as drinking water supply, were monitored seasonally for one year. We collected samples of surface and deep waters. ELISA test was performed to detect sum of CTX microcystins (MCs) and nodularins (NOD). Also, for each sample, CB species were identified.Planktothrix rubescens, Pseudoanabaena sp., Limnothrix redekei, Borzia sp., Merismopedia sp., Oscillatoria sp., Dolichospermum sp. Picocyanobacteria were found in the studied basins. Sums of MCs and NOD were detected in each sample and their concentrations ranged between 2 ng/L and 669 ng/L.Presence of toxic CB (especially P. rubescens) in Sicilian lakes, whose waters are used for drinking purposes, could represent an important risk for human health. Variability of species in a same basin could lead to the selection of the most harmful one and to increase of MCs in drinking waters. In one year of monitoring we usually detected low concentrations of CTX, but in some cases they were close to the reference value that WHO assessed for drinking water (1 µg/L). Even if LC-MS and molecular confirmation are needed, our results suggest that a more regular and frequent surveillance is necessary to minimize risk for human health.