Nitrite Toxicity to Danio Rerio: Effects of Fish Age and Chloride Concentrations

The aim of the present study was to compare the acute nitrite toxicity for Danio rerio at the age of 20-25 days (larval stage) and 2-3 months (juvenile stage) at various chloride concentrations. The semistatic method according to OECD 203 was used in the tests. The 96hLC50 NO 2 - value was 386.00 ± 29.75 mg l -1 ( D. rerio aged 20-25 days), and 242.41 ± 13.67 mg l -1 ( D. rerio aged 2-3 months), respectively, at 19 mg Cl - l -1 in diluting water. We observed an increase in 96hLC50 NO 2 - in D. rerio of both developmental stages following an increase in Cl- concentration in diluting water. A comparison between the 96hLC50 NO 2 - determined for D. rerio aged 20-25 days and those aged 2-3 months at different chloride concentrations in diluting water (19; 50; 100 mg l -1 ) showed a highly significant increase ( p < 0.01) in the 96hLC50 NO 2 - for the younger fish at all chloride concentrations. An exponential relationship between 96hLC50 NO 2 - values and chloride concentrations in diluting water (I = 0.849) was demonstrated in D. rerio aged 20-25 days while a logarithmical relationship (I = 0.856) was observed in D. rerio aged 2-3 months.