Schrader, KK; de Regt, MQ; Tidwell, PD; Tucker, CS; Duke, SO

Aquaculture, vol. 163, no. 1-2, pp. 85-99, 1 Apr 1998

Oscillatoria cf. chalybea produces the musty, off-flavor compound 2-methylisoborneol which can taint the flesh of channel catfish and render them unmarketable. Green algae are preferred over cyanobacteria in aquaculture ponds since they do not produce 2-methylisoborneol and because they are better in maintaining the primary productivity in pond ecosystems. The discovery of compounds exhibiting selective toxicity towards cyanobacteria is the first step in the development of a cyanobacterial algicide that would benefit the channel catfish industry. Herbicides and other synthetic compounds were screened using a microplate bioassay to determine their toxicity towards the cyanobacterium O. cf. chalybea and the green alga Selenastrum capricornutum. Diquat, paraquat, and diuron were most inhibitory to the growth of O. cf. chalybea (0.1, 0.1, and 1.0 mu M, respectively) but only diquat and paraquat were selectively toxic towards O. cf. chalybea. Bromoxynil, cinmethylin, diclofop, isoxaben, and sodium carbonate peroxyhydrate were selective, with complete growth inhibition towards O. cf. chalybea. Of these compounds, sodium carbonate peroxyhydrate appears to be the most environmentally and toxicologically safe for use in aquaculture. Sodium carbonate peroxyhydrate may not be selectively toxic against all species of cyanobacteria, as evidenced by our additional screening of the compound using another cyanobacterium, Anabaena sp.