Effects of environmental ammonia concentrations on tribenuron methyl toxicity in Daphnia magna

The aim of the present study is to investigate the toxicity of the herbicide tribenuron methyl as an anthropogenic agent and ammonia as an abiotic factor on Daphnia magna at their environmental levels. They may coexist in the same environment. For this aim, D. magna specimens were exposed to tribenuron methyl and two different environmental levels of ammonia in 96 hours subacute and 21 days chronic durations. GPx, GST, tChE enzyme activities and TBARS and total protein concentrations were determined spectrophotometrically. MMP was analysed by fluorescence staining. Cytochrome c and AMPK protein concentrations were analysed by Western blotting. GST, tChE enzyme activities and TBARS and total protein levels did not change during subacute experiments. GPx activity increased in higher ammonia and tribenuron methyl mixture group compared to single administration groups of these toxicants. MMP depolarized in all the exposure groups; while it most affected in higher ammonia and tribenuron methyl mixture group. Cytochrome c protein level elevated in the effect of lower ammonia and lower ammonia and tribenuron methyl mixture groups. AMPK protein level increased in all the exposed daphnids except the lower ammonia exposure group. According to our results, GST and tChE cannot be considered as a biomarker for ammonia and tribenuron methyl intoxication in D. magna. The most probably, ammonia and tribenuron methyl caused an energetic crisis in D. magna but in discrete mechanisms. MMP and AMPK might be used as a good biomarker for these toxicants.