Population and biomarker responses of Daphnia magna towards anticholinesterase exposures

Abstract Context: Cholinesterase (ChE) had long been employed for revealing environmental existence of anticholinesterases, and β-N-acetylglucosaminidase (NAGase) is a newly developed biomarker of aquatic arthropods. Still, population consequences of ChE inhibition and the consequences in terms of NAGase remained unclear. Objective: To quantify relationship between level of ChE and that of NAGase deliberated from chemical suppressed population of Daphnia magna. Methods: A set of macrophyte-dominated systems were established indoor to test insecticide chlorpyrifos. Antibodies were developed for quantifying content of ChE in bodies and content of NAGase in media, which was achieved by indirect-competitive and indirect-noncompetitive enzyme-linked immunosorbent assay (ELISA), respectively. Results: Lowest observed effect concentration (LOEC) of chlorpyrifos, as it was counted by actual concentrations, was 0.128, <0.011, 0.092, and 0.092 µg/L for population density, inherent activity of ChE, apparent activity of ChE, and content of NAGase, respectively. Corresponding to 0.90–0.48 U/µg declination in inherent activity of ChE, atrophy of −1.65 to 23% in population and that of −4.1 to 24.89% in NAGase was detected, respectively. Conclusion: Population impact of an anticholinesterase could be predicted, with adequate accuracy, by either ChE or NAGase.