Abstract
The effects of two widely used pesticides in paddy fields, 2, 4-D, dimethylamine and endosulfan, on growth, photosynthetic rate and the photosynthetic pigments of Chaetoceros sp. and Nannochloropsis sp. were assessed in this study. The 48 hour 50% inhibitory concentration (IC 50 ) value for 2, 4-D dimethylamine on Chaetoceros sp. and Nannochloropsis sp. were 142.2 mg l−1 and 211.8 mg l−1, respectively, and the 48 hour IC 50 value for endosulfan on Chaetoceros sp. and Nannochloropsis sp. were 21.9 μ g l−1 and 45.8 μ g l−1, respectively. Endosulfan was much more toxic to the microalgae than 2, 4-D dimethylamine. Both pesticides reduced photosynthetic pigments and oxygen production rate of the microalgae. After 48 hours exposure to the pesticides, the microalgae were transferred to a pesticide-free medium to investigate the post-exposure effect. 2, 4-D dimethylamine and endosulfan did not cause irreversible damage on the microalgae. However, there was a prolonged lag phase and the maximum specific growth rate (μ) of the microalgae was significantly retarded.
Acknowledgements
The authors would like to acknowledge the Ministry of Higher Education, Malaysia and University Malaysia Terengganu for funding the studies.