Impact of nitrate on growth and survival of embryo and larvae of the green toad, Bufotes variabilis (Anura: Bufonidae)

Amphibian populations are declining on a global scale, and many contributing factors have been implicated, including the effect of agricultural contaminants. Nitrate is heavily used as an agricultural fertilizer and is today a ubiquitous environmental pollutant. In order to test the influence of nitrate on growth and survival of embryonic and larval of the green toad Bufotes variabilis, 300 eggs were raised separately at four concentrations of 0: control, 13.7, 34.5, 57.5 mg/L during 74 days. The experimental results showed that the nitrate had a non-significant effect on hatching time and rate (p> 0.05) during the embryonic period. The results show average values for snout-vent length (SVL) for larvae measured in the four treatments of concentrations on 74 days was the highest in the control treatment (10.61±0.28 mm), followed by 13.7 mg/l (10.52±0.74), 34.5 mg/l (10.41±0.71), and 57.5 mg/L concentrations of nitrate (10.34±0.52) but this is not significant (p<0.05). Larvae in the 57.5 mg/l concentration exhibited the lowest mean of growth rate for SVL (0.16 mm/days) and 13.7 mg/l exhibited the greatest mean of growth rate (0.17 mm/days) at the end of the experiment.The percentage of larvae remaining at the end of the experiment was 89.33%±2.30, 73.33%±2.30, 70.66%±9.23, 57.33%±16.16, for the control, 13.7, 34.5, 57.5 mg/l treatments, respectively. The results of ANOVA indicated the impact of nitrate on the survival of larvae B. variabilis was significant (p≤0.006)

Keywords:

Amphibian declines , Growth , survival , Nitrogen pollution