A SURVEY OF TOXICITY OF CYANOBACTERIAL BLOOMS IN LAKE-LADOGA AND ADJACENT WATER BODIES

Twentyfive cyanobacterial blooms in Lake Ladoga and adjacent water bod ies were studied in the summer of 1990-1992. Toxicity of the water blo om material for mice was detected in 9 cases. The maximal tolerable do ses (MTD) of the material extracted from biomass varied within 3-30 mg kg(-1) mouse body weight; 50% lethal doses (LD(50)) were within 45-12 5 mg kg(-1). Toxic water blooms were registered in Karelian lakes and in the Neva Bay, Gulf of Finland. Cyanobacterial samples collected on the eastern coast of Lake Ladoga proved to be non-toxic. The species i dentified in toxic bloom material included Anabaena circinalis, A. flo s-aquae, A. lemmermannii, Anabaena sp., Aphanizomenon flos-aquae, Gloe otrichia echinulata, G. pisum, Microcystis aeruginosa and Oscillatoria sp. These data suggest that toxic forms of cyanobacteria are widespre ad in Karelian lakes belonging to the drainage basin of Lake Ladoga.