Assessment of rapid bioassays for detecting cyanobacterial toxicity

Simple and easy-to-use bioassays with Artemia salina (brine shrimp) larvae, luminescent bacteria and Pseudomonas putida were evaluated for the detection of toxicity due to cyanobacterial hepato- and neurotoxins. The hepatotoxins and a neurotoxin, anatoxin-a, were extracted from laboratory-grown cultures and natural bloom samples by the solid phase fractionation method and dissolved in diluent for different bioassays. The toxin concentration of cyanobacterial extracts was determined with HPLC. The Artemia biotest appeared to be quite sensitive to cyanobacterial hepatotoxins, with LC 50 values of 3-17 mg l-1. The Artemia test was also shown to be of value for the detection of toxicity caused by anatoxin-a. The fractionated extract of anatoxin-a was not lethal to Artemia but it disturbed the ability of the larvae to move forwards. Filtered cyanobacterial cultures with anatoxin-a, on the other hand, caused mortality of Artemia larvae at concentrations of 2-14 mg l-1. With the solid phase fractionation of cyanobacterial samples, no non-specific toxicity due to compounds other than hepato- and neurotoxins was observed. In the luminescent bacteria test, the inhibition of luminescence did not correlate with the abundance of hepatotoxins or anatoxin-a. The growth of Ps. putida was enhanced, rather than inhibited by cyanobacterial toxin fractions.