Ecological Hazards of Some Pesticides on Unicellular Freshwater Green Alga; Pseudokirchneriella subcapitata

Document Type : Original Article

Authors

1 Mammalian and Aquatic Toxicity Dept., Central Lab of Agricultural Pesticides, Agricultural Research Center, Alexandria, Egypt.

2 Pesticide Chemistry and Toxicology Dept., Faculty of Agriculture (Fuka Branch)Alexandria University, Marsa Matrouh, Egypt.

Abstract

Aquatic toxicity and differential sensitivity of different pesticide categories on freshwater green alga; Pseudokirchneriella subcapitata were investigated. In this context, growth-inhibiting tests of 14 pesticides (including 4 fungicides; 4 acaricides/ nematicides and 6 insecticides) were carried out.  Based on IC50 values, P. subcapitata was more sensitive to many pesticides (mostly fungicides and acaricides/ nematicides) and less sensitive to insecticides. The test alga was tolerant to carbendazim, while it was highly susceptible to prochloraz. The 96-h IC50 values for imidazole and benzimidazole fungicides; prochloraz and thiallophanate-methyl varied around 0.26 and 80.81 mg/L; respectively, while organophosphates (chlorpyrifos-methyl, chlorpyrifos, profenofos, fenamifos, malathion and dimethoate) varied in their toxicities from 1.01 to 42.67 mg/L. Furthermore, carbamates (mancozeb, methomyl, carbosulfan and carbendazim) showed different patterns of IC50s (0.27, 72.96, 246.06 and 393.26 mg/L; respectively). According to estimated risk phrases, the decreasing order of the potential aquatic ecosystem risk imposed by the tested pesticides was prochloraz > mancozeb+metalaxyl > chlorpyrifos-methyl > chlorpyrifos > imidaclopride > profenofos > fenamifos > malathion > dimethoate > methomyl > thiallophanate-methyl > carbosulfan > mineral oil > carbendazim. In conclusion, the results of this study clearly emphasize the importance of estimating risk phrases when assessing the pesticide stress on aquatic ecosystems and indicated that the tested pollutants may imbalance the aquatic ecosystem and cause a shift of algal species dominance. Such speculations need further more studies to fully understand the processes involved in pesticide toxicity.
 

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