CYANOBACTERIA BLOOM IN THE OCCHITO ARTIFICIAL LAKE (SOUTHERN ITALY): RELATIONSHIP BETWEEN Planktothrix rubescens DENSITY AND MICROCYSTIN CONCENTRATION

During the winter season 2008/2009 for the first time a massive cyanobacteria bloom occurred in the artificial lake of Occhito, the main reservoir in the province of Foggia (Southern Italy, Apulian Region). The toxic species Planktothrix rubescens was identified and monitored from January to July 2009 in order to quantify the population density and microcystin production both in the lake and in treated waters for human consumption. The bloom reached the main peak during March 2009, when the highest values of 140-160*10(6) cells/1 were recorded in the lake (at the same time the microcystin concentration was 11-31 mu g/l). The water treated by means of sand - activated carbon filtering and chlorination processes highlighted significant removal rates, from 34% to 99% for P. rubescens cell density and from 52% to 100% for microcystin.