NON-TARGET EFFECT OF MALATHION AND 2, 4-D ON TEA-GARDEN SOIL ALGAEKAMAL CHOUDHURY AND SIKHA RANI KALITAAbstract In agricultural fields during the past few decades, pesticides have been used frenziedly though it is not an appropriate measure of sustainable practice. Microalgae easily become the first, in the list of non target organisms that are affected by pesticides. The present investigation deals with the studies on the effects of selected pesticides - Malathion and 2, 4-D on algae from the Tea Garden soils. Malathion is an organophosphate insecticide and 2, 4-D (Dichlorophenoxy acetic acid) is a herbicide which are commonly used for agricultural protection in our country. In control, total 29 algal species were observed, out of which 16 belongs to Cyanophyceae, 9 Chlorophyceae and 4 Bacillariophyceae. The tested concentrations of pesticides were 50, 100, 200, 400 and 600 ppm. Among the two pesticides Malathion is found to be more toxic then 2, 4-D. The toxic level of Malathion is higher in Bacillariophyceae than Chlorophyceae followed by Cyanophyceae. In case of 2, 4-D the Bacillariophyceae shows the same trend but Cyanophyceae is more toxic than Chlorophyceae. In this observation Lyngbya limnetica and Chlorella vulgaris were appeared as most tolerant species for both the pesticides. On the other hand Aulosira fertilissima, Calothrix marchica, Oedogonium gracillus, Closterium diane, Fragillaria brevistrata and Tabelaria fenestrate were found to be very sensitive to both the pesticides. |