Abstract:
Fungicides have the potential to deleteriously affect the non-targeted aquatic microbial
communities, macroinvertebrates communities and key ecosystem processes such
as litter decomposition, nutrient recycling. Tebuconazole (TBZ) is a commonly used
fungicide in agricultural areas in Sri Lanka. Although a few research looked at how
other fungicides affected decomposer communities and aquatic ecosystem processes
including leaf litter decomposition, there were no studies on Tebuconazole’s effects on
stream ecosystems. The present study aimed at investigating the effects of TBZ on
Terminalia arjuna decomposition in tropical streams. A 40-day indoor microcosm study
was conducted to evaluate the leaf litter breakdown rate of Terminalia arjuna subjected
to TBZ concentrations of 0.1mg/L, 1mg/L and control tanks with dechlorinated water.
The leaf Decomposition Rates (DR) were analysed using the %Dry weight reduction
(%DWR) and %organic matter reduction (%OMR) using ANCOVA keeping time as a
covariate in microcosms. Dunnett’s post hoc test was used to determine the significant
differences among treated and control channels. The results indicated that there was a
lower decay coefficient (k) for TBZ treated leaf packs in comparison to control leaf packs
(k control: -0.0104±0.0005> k 0.1mg/L: -0.0093±0.0007> k 1mg/L: -0.0087±0.0002),
suggesting a delay in DR when exposed to TBZ contamination. There was a significant
reduction of % dry weight in control tanks in comparison to treatment tanks (p<0.05)
while no significant difference (p>0.05) of %OMR among the leaf packs in treated and
control tanks. The finding of the study suggests that the fungicide TBZ can harm the
non-target aquatic fungi which are not resistant to TBZ contamination thus affecting
the leaf litter decomposition process. A high concentration of TBZ exposure suppresses
the leaf litter decomposition process.
