EL-Nahhal Yasser, Alshanti Adli
The present study was designed to investigate the disappearance of cyanobacterial mat from fish breeding lakes and to evaluate the phytotoxic effects of Penicillin, Ciprofloxacin, and Tylosin as single and as mixtures to cyanobacterial mats. Phytotoxic effects were measured as growth inhibition of cyanobacteria using spectrophotometer at 680 nm at low concentrations of antibiotics. Results showed potential phytotoxicity of the tested antibiotics with EC50 values of Penicillin, Ciprofloxacin and Tylosin of 0.13, 0.71, 5.28 mg/l respectively. Relative toxicity indicated that Penicillin and Ciprofloxacin were more toxic to cyanobacterial mats than Diuron (standard toxic material). EC50 values of binary mixtures are 0.077, 0.103, 0.292 TU, for (Penicillin+Tylosin), (Ciprofloxacin+Tylosin) and (Ciprofloxacin+Penicillin) respectively; whereas EC50 of the tertiary mixture is 0.034 TU. Statistical analysis of the results indicated significant differences between the toxic effects of compounds and their mixtures to cyanobacterial mats. Observation of toxicity of over time indicated that cyanobacterial mats were able to overcome the toxic effects after approximately 72 h of exposure time. It can be concluded that antibiotics exert dangerous toxic effects to cyanobacterial mat, an important organism in the eco-system. These results are considered the first of its kind in Palestine.
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