Stimulatory effect of herbicide 2,4-D on the heterotrophic microbial community in the water of three fish ponds.

Herbicide 2,4-D at a dosage of 500 mg l-1 stimulated the proliferation of the heterotrophic bacterial community present in the water of three fish ponds over a period of one year. 2,4-D due to its toxic action might kill the planktonic algal population occurring in the pond water, which on degradation generated more nutrients conductive to bacterial proliferation. The microbial density in different hours were closely correlated (p less than 0.01 less than 0.05) with the variations of each of NH4-N, NO2-N and specific conductivity of water, while the relationship between the former and PO4-P was reciprocal (P less than 0.001).