Effects of tebufenpyrad on freshwater systems dominated by Neocaridina palmata, Physa fontinalis, and Ceratophyllum demersum.

Tebufenpyrad are widely used for control leaf mites in orchard and may enter freshwater systems through runoff, spray drift, and so on. Few papers have reported the side effect of the pesticide on population dynamics of aquatic taxa such as shrimps, gastropods, macrophytes, phytoplankton, and bacteria. Here, we tested the effect of a single application of tebufenpyrad on Neocaridina palmata, Physa fontinalis, Ceratophyllum demersum, Simocephalus vetulus, Dolerocypris sinensis, and so on, by indoor systems. The TWA (Time-weighted average)-based highest no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for Neocaridina palmata, which were counted by the wet weight, were 0.67 and 2.33 µg/L, respectively, and the dose-related effect lasted 21 d. According to our study, chitobiase could be used to quantify the effects of the pesticide on shrimp despite the interference from P. fontinalis, which was finally corrected by employing of antibodies. The NOEC and LOEC were thus determined to be 1.41 and ≤ 5.64 µg/L, respectively, which were higher than the values that was counted by the wet weight. Principal component analysis (PCA) and principal response curve (PRC) investigation showed that the pesticide suppressed population of C. demersum, and phytoplankton, while the Physa fontinalis, S. vetulus, and D. sinensis were stimulated by the pesticide. Illumina MiSeq was used to determine the alteration in bacterial community within the systems. The results of PRC and PCA analyses showed that tebufenpyrad induced flora of nitrate reducing, nitrate denitrifying, thiosulfate oxidation, ureolysis, and methanol oxidation, while it suppressed flora of cellulolysis. Tebufenpyrad was found to have a negative effect on water quality indicators such as pH, DO, NO3-, NO2-, and SO42-, and a positive effect on PO43-, NH4+, and EC. This suggested that the tebufenpyrad led to water quality deterioration.