RESUMEN
Bentazon (Basagran®) belongs to the chemical group of benzothiadiazinones. Thus, this study aimed to estimate the influence of herbicide bentazon (3 µg.L-1, 6 µg.L-1, 12 µg.L-1, 300 µg.L-1) in Danio rerio embryos development. The study tested environmental relevant concentrations of bentazon as well as the limit established for drinking water (300 µg.L-1) in Brazil. We performed behavioral and developmental analyzes during 96 h of exposure. The bentazon measurements after experimental period showed reduction ranging from 5.0 to 18.93% between exposed groups. Our results showed significant differences in the heart rate, which was significantly higher in groups exposed to all bentazon concentrations compared to control groups. The absence of alterations in the behavioral parameters showing that the herbicide bentazon at the concentrations tested had few adverse effects on the development and behavior of the Danio rerio embryos. Considering the toxic point of view, there is a chance that bentazon acts together with other environmental contaminants as an additive or synergistic way.
Asunto(s)
Herbicidas , Contaminantes Químicos del Agua , Animales , Herbicidas/toxicidad , Pez Cebra , Benzotiadiazinas/toxicidad , Desarrollo Embrionario , Contaminantes Químicos del Agua/toxicidad , Embrión no MamíferoRESUMEN
Chlorophyll fluorescence techniques are used for the detection of toxic substances in samples of photosynthetic cells by measuring chlorophyll a fluorimetric parameters, which are a response of the PSII physiological status. This work was conducted to determine the effects of the herbicide bentazon (CASRN 25057-89-0) on growth and maximum quantum yield of photosystem II (Fv/Fm) in cells of the marine diatom Skeletonema costatum. Unialgal cultures were exposed to several bentazon concentrations and its effects on algal growth and Fv/Fm were determined. The traditional algal growth inhibition test (algal biomass measurements) and DCMU-induced chlorophyll a variable fluorescence measurements were determined. Our results showed that even low concentrations of bentazon rapidly lead to Fv/Fm decrease, while the effects on algal growth were detected after 24 h of exposure. The LOEC (2.81 mg L(-1)) and EC50 (13.0 mg L(-1)) determined through Fv/Fm experiments were lower than the LOEC (22.5 mg L(-1)) and EC50 (24.0 mg L(-1)) determined through algal growth inhibition experiments. This confirms that the Fv/Fm is a more sensitive parameter than algal growth for monitoring the effects of bentazon. The present results have demonstrated the applicability of Fv/Fm parameter to access the early toxicity of bentazon, as well as other PSII-inhibition compounds, before significant changes occurred in the original concentration and bioavailability of these toxicants during longer exposure times.