Studies on the effects of the insecticide aldrin on aquatic microbial populations

The effects of aldrin at rates 10 and 50 mgml−1 on microbial function were studied under aerobic conditions. Parameters monitored included total culturable population of heterotrophic bacteria, number of culturable phosphate-solubilizing microflora, number of bacteria which decompose protein with liberation of H2S, nitrifying bacteria, denitrifying bacteria and denitrification activity. Culturable heterotrophic bacteria, phosphate-solubilizing bacteria, bacteria which decompose proteins with liberation of H2S and denitrifying bacteria were significantly increased at dose rates of 10 and 50 mgml−1 of aldrin. However, the presence of aldrin decreased denitrification activity at concentration of 50 mgml−1. Nitrifying population were not affected as a consequence of the addition of aldrin, showing that these microorganisms can tolerate the concentrations of aldrin tested.