Effects of Biodegradable Insecticides on Biofilter Bacteria: Implications for Aquaponics

Abstract

Even though aquaponics is the production system that is increasingly gaining focus, there is an absence of publications studying the use of pesticides in the aquaponics. Therefore, the aim of this study was to assess negative effects of one synthetic (chlorpyrifos) and two botanical insecticides (azadirachtin and pyrethrin) to matured biofilter in plastic buckets. The effectiveness of biofilter bacteria is determined indirectly, as concentrations of ammonia, nitrites and nitrates in the water were measured at 0h, 5h, 13h, 21h, 29h, 37h, 45h and 53h after insecticides application. The results showed negative effects of azadirachtin on the first step of nitrification, as concentration of ammonia was higher comparing to other groups for almost every sample point. Negative effects on second step of nitrification and higher concentrations of nitrites in the water were also detected, but no statistical differences were observed in the present study, due to the large variation between buckets. Nitrates were lower in water treated with azadirachtin from 29 hours from start to the end of the experiment. Application of other two insecticides to biofilter did not cause any effects and showed no difference comparing to the control group.