The Potential of the Thamnotoxkit Microbiotest for Routine Detection of Cyanobacterial Toxins
Abstract : An interlaboratory trial with 8 laboratories was organised for evaluating the potential of the Thamnotoxkit F™ microbiotest for toxicity detection of 5 toxin producing cyanobacteria (Anabaena flos-aquae, Microcystis aeruginosa, Cylindrospermopsis raciborskii, Aphanizomenon flos-aquae, Tychonema bourrellyi) and the green alga Selenastrum capricornutum(Raphidocelis subcapitata) as a control. The Thamnotoxkit F™ test is a 24h bioassay using, as test organisms, larvae of the freshwater anostracan crustacean Thamnocephalus platyurushatched from cysts. Dilution series were prepared from freeze-dried samples of microalgae which were submitted twice to freezing and melting before extraction of the water soluble cyanotoxins. The concentration series used for each microalgal extract ranged from 0.3 mg/ml to 5.0 mg/ml. All samples were tested twice at different time by each examiner, eventually yielding 16 independent results obtained from 3 parallels (48 data for each sample). The samples of C. raciborskiiwere only studied by 4 examiners and gave 8 results (24 data). The water extracts of An.flos-aquaeand M. aeruginosawere the most toxic to T. platyurusinducing 100% mortality in all concentrations used, except the highest dilution in which the mortality was, however, still around 70-80%. The extracts of C. raciborskiialso induced 100% mortality as from the 1.0 mg/ml concentration and Aph.flos-aquaekilled all the test organisms at the 3.0 mg/ml dilution. Water extracts of T. bourrellyionly caused total mortality in the highest test concentration. The water extract of the control alga S. capricornutumonly gave a significant toxicity effect (around 30%) on the crustaceans in the highest concentration.
From this study it can be concluded that the Thamnotoxkit F™ assay is a sensitive and convenient method for the detection of cyanotoxins and constitutes an interesting alternative for the mouse bioassay for routine hazard screening of water bodies for biotoxins.