Individual and Combined Effects of Pesticides with Active Ingredients of Mancozeb and Methomyl on the DNA Damage of Daphnia magna (Straus, 1820; Cladocera, Daphniidae)

Mancozeb and methomyl are active ingredients commonly contained in pesticides applied in shallot farming. Surface runoff can carry pesticide residues that enter water bodies and affect non-target organisms, such as Daphnia magna. This study evaluated the genotoxicity effects of individual and combined mancozeb and methomyl on the DNA damage of D. magna. Organisms at 24 h old and 48 h old were exposed to individual and combined concentrations of mancozeb and methomyl for 24 h to obtain the LC50-24 h values. These values were used to evaluate DNA damage by calculating the tail intensity (TI) (), tail moment (TM), and tail factor (TF). Results showed that based on the LC50-24 h values, methomyl has the highest toxicity level, followed by the mancozeb:methomyl combination, and then mancozeb. The combination index of mancozeb:methomyl for both D. magna ages (24 h and 48 h) indicated that the two pesticides antagonistically interact (CI>1). However, based on TI, TM, and TF values, the level of damage was almost the same between the individual and combined pesticide concentrations, and the DNA damage was more massive with increased pesticide concentration. The DNA damage of 24 h old and 48 h old D. magna did not significantly differ. Increased DNA damage in D. magna indicated that this parameter was sensitive to the presence of pesticides. In application, DNA damage can be used as a biomarker for biomonitoring pesticide pollution in the aquatic ecosystem. © 2023, Faculty of Environment and Resource Studies,Mahidol University. All rights reserved.