Effects of sumithion on growth and production of phytoplankton and zooplankton in aquaculture ponds

Sumithion is an organophosphorous pesticide widely used to control tiger bugs in fish larval rearing pond. The present study was aimed to investigate the effects of sumithion on plankton population abundance in aquaculture pond. The experiment was carried out with three treatments, i.e. ponds with no sumithion (T1), ponds with 1.0 ppm sumithion (T2) and those with 2.0 ppm sumithion (T3). The water quality parameters, such as temperature, pH, dissolved oxygen and total alkalinity were almost unchanged throughout the study period whereas transparency, NO3-N and PO4-P values declined with an increase in sumithion concentrations but differences were not significant (p<0.05). No distinct changes were observed in population densities of phytoplankton (x cells L-1). On the other hand, the zooplankton population densities (x Ind L-1) significantly (p<0.05) decreased with toxicity of sumithion after 30 days up to the end of experimental period in both T2 and T3 compared to the control group (T1). The ranges of pH, organic carbon (%), available phosphorus (ppm) and total nitrogen (%) of pond bottom-sediment did not differ irrespective of the treatments. This study demonstrated that sumithion has adverse effects on zooplankton which may influence the production in aquaculture pond.