The influence of low concentration of cypermethrin and deltamethrin on phyto- and zooplankton of surface waters.

Pyrethroids play an important role in modern agriculture but their use is not without risks to non-target organisms and habitats. They have high toxicity to a broad spectrum of aquatic organisms. The aim of the study was to investigate the effect of low concentration (0.02 μg l(-1)) of two widely used pyrethroids--cypermethrin and deltamethrin on phyto- and zooplankton. The acute bioassays were conducted using Chlorella vulgaris and Thamnocephalus platyurus. Then, the chronic bioassays were conducted using Chlorella vulgaris, Daphnia magna and Brachionus calycilforus. The 24h LC50 values for cypermethrin and deltamethrin to Thamnocephalus platyurus were 0.89 μg l(-1) and 1.51 μg l(-1), respectively. The 48h EC50 values for cypermethrin and deltamethrin to Brachionus calycilforus were 3.828 mg l(-1) and 8.425 mg l(-1), respectively. 13% growth inhibition of Chlorella vulgaris (statistically insignificant) after 14 days of exposure to deltamethrin as well as cypermethrin was observed.