Preliminary evidence of toxicity associated with the benthic cyanobacterium Phormidium in South Australia

In April 2000, the water supply for Yorke Peninsula in South Australia was deemed nonpotable when extracts from a proliferation of the benthic cyanoba cterium Phormidium aff. formosum in Upper Paskeville Reservoir were found t o be lethally toxic by intraperitoneal injection into mice (400 mg kg(-1)). Routine water quality monitoring had failed to detect the development of t he Phormidium until complaints of musty taste and odour, attributable to th e production of 2-methyl-isoborneol (MIB), were received from the consumers . The 185 ML open-balancing storage, receiving filtered and chloraminated w ater from the River Murray, was isolated from the drinking water supply and a health alert was issued to approximately 15,000 consumers. The identity of the toxin(s) is thus far unknown, but clinical symptoms of toxicity in m ice and chemical characteristics are distinct from the known major cyanotox ins. Preliminary characterisation of this toxin indicates that it has low s olubility in water and organic solvents and is strongly associated with the particulate cellular material of the filaments. Toxicity of extracts was d iminished by boiling and by treatment with chlorine, but not by chloramines . Further testing of floating cyanobacterial mats in the Torrens Lake in th e city of Adelaide (Phormidium aff. formosum) and Myponga Reservoir (Phormi dium aff. amoenum) in 2000/2001 was also found to be toxic by mouse bioassa y. Toxicity is yet to be confirmed in monospecific cultured strains and fur ther studies are required to identify the toxin and assess its health signi ficance. Genetic characterisation of isolates has commenced in an attempt t o classify their relatedness and to assist in the rapid identification of p otentially toxic strains. (C) 2001 by John Wiley & Sons. Inc.