Effect of pesticides on phytoplankton production

The effect of pesticides on natural phytoplankton was determined by incubating the plankton samples in situ at 1 m depth for different periods with various concentrations of the following pesticides: PP,-DDT, lindane, endosulfan (Organochlorine), methyl parathion, malathion (Organophosphorus) and sevin (carbamate). Primary production was inhibited considerably by these pesticides. In most cases production decreased with increase in the concentration of the pesticides. The production values ranged from 24.1 to 89.07 of that of the control for the six pesticides tested. The organochlorine pesticides were found to be more toxic than the other two groups and carbamate (sevin) was the least toxic to phytoplankton. The toxic effect was in the order of PP - DDT is greater than endosulfan is greater than lindane is greater than methylparathion is greater than malathion is greater than sevin