ISOLATION OF MICROCYSTIN-LR FROM A MICROCYSTIS (CYANOBACTERIA) WATERBLOOM COLLECTED IN THE DRINKING-WATER RESERVOIR FOR PORTO, PORTUGAL

Plankton tows collected over the water intake towers on Crestuma reser voir, which is the drinking water supply for about 2,000,000 persons i n the Porto, Vila Nova de Gaia, and Gondomar regions near the city of Porto, were found to be hepatotoxic using the mouse intraperitoneal bi oassay. Phytoplankton in these samples was dominated by the cyanobacte ria Microcystis aeruginosa (95%). The lethal dose for 50% of the anima ls tested of lyophilized bloom material was approximately 30 mg/kg (dr y cell weight/animal weight). Using HPLC separation, a single fraction was obtained. Isolation and purification of this fraction resulted in a toxin that was shown to be microcystin-LR by amino acid and MS anal yses. Since microcystin-LR is a potent hepatotoxin and liver tumor pro moter, and since high cell densities of Microcystis aeruginosa produci ng microcystin-LR were found near the water intake lines, it shows tha t a regular monitoring of microcystin(s) should be developed in water used for human consumption to prevent any health hazard. The eutrophic ation of the Douro River due to agricultural runoff, domestic effluent s, and effluents from large Spanish towns leads us to conclude that M. aeruginosa toxic waterblooms will continue to occur and possibly incr ease during periods of low rainfall and warm weather. This creates the distinct possibility that human and animal intoxications will occur. We recommend that regulations concerning the control of microcystins i n waters be developed in countries where this problem occurs. A nation al program in Portugal to inform the public about the possibility of c yanobacteria intoxication is also recommended.