Humic material changes effects of terbutylazine on behavior of zebrafish (Brachydanio rerio)

The long-term sublethal toxicity of the triazine herbicide terbutylazine (TBA, 1, 5, 50, 200 μg/l) alone and in presence of dissolved humic material (DHM, 2 mg TOC/l) on zebrafish (Brachydanio rerio) has been studied. The effect of the tested substances on behavior were investigated by recording and quantifying their spontaneous locomotor activity using the BehavioQuant® system. Data were analysed by the Hasse diagram technique. For the parameter light-dark-preference, but not for the parameter inconstancy of motility, a clear concentration-effect-relationship for the groups under TBA as well as for the groups under TBA + DHM exposure could be found. Comparing TBA and TBA + DHM treated groups for both test parameters the presence of DHM increased the toxic effect of TBA on zebrafish for the preference and decreased for the motility. The main result is that the preference follows an additive principle, but not the motility. Hints for the influence of at least two different mechanisms controlling these behavioral parameters are discussed.