草甘膦与氰氟草酯对隆线溞的急性毒性研究

在水生食物链中,水溞是连结植物、微生物和动物的关键成员。草甘膦与氰氟草酯被广泛用于防除水生和稻田杂草,研究它们对水溞的毒性,有益于人们关注使用除草剂对水体生态系统的影响。试验以标准水体监测生物——隆线溞(Daphnia carinata)单克隆为材料,研究草甘膦和氰氟草酯对其泳动能力、存活率和趋光性的影响。结果表明,两种除草剂对隆线溞均有明显毒性,草甘膦对隆线溞24,48和96h的半致死浓度(LC50)分别为66.58,29.60和12.33mg/L,为田间常规用药量的0.15%~0.81%;氰氟草酯对隆线溞24,48和96h的LC50依次是63.15,51.91和34.41mg/L,为田间常规用药量的17.21%~31.58%。两种除草剂显著影响隆线溞的泳动能力和趋光指数。隆线溞接触草甘膦和氰氟草酯3h后,导致其趋光指数显著改变的浓度分别是4.59和14.20mg/L,分别为常规用药量的0.06%和7.10%。因此,草甘膦和氰氟草酯对水溞的毒性大,对水生食物链的影响不可忽视。利用水溞趋光性可快速、灵敏地监测除草剂使用后的水体生物毒性。

Acute toxicity study of glyphosate and cyhalofop-butyl to Daphnia carinata

Daphnia is a key organism in the food chains of plants,microbes,and animals in aquatic ecosystems.Glyphosate is widely applied to crop fields,orchards,green land,and water,and accounts for about 60％ of registered herbicides in China.Cyhalofop-butyl is widely used to control Echinochloa crusgalli in paddy fields.The use of these two herbicides has increased markedly in recent years in China.Therefore,it is important to investigate the toxicity of glyphosate and cyhalofop-butyl to zooplankton to understand their effects on aquaticecosystems.In this study,Daphnia carinata,a standard bio-monitor of water quality,was cultivated in dechlorinated tap water and fed with Scenedesmus obliquus at (20±0.5) ℃ under light at 1200 lx supplied by fluorescent lamps.Four-day-old D.carinata were incubated in solutions containing glyphosate or cyhalofop-butyl at different concentrations.The acute toxicity of these two herbicides to the movement,survival,and phototaxis of D.carinata was evaluated.Both herbicides were toxic to D.carinata.The semi-lethal concentration (LC50) of glyphosate in 24 h,48 h,and 96 h was 66.58,29.60,and 12.33 mg/L,respectively,and that of cyhalofop-butyl was 63.15,51.91,and 34.41 mg/L,respectively.These dosages represented only 0.15％-0.81％0 (glyphosate) and 17.21％-31.58％ (cyhalofop-butyl) of those applied in the field.Both glyphosate and cyhalofop-butyl had significant adverse effects on the swimming ability and phototaxis index of D.carinata.The concentrations causing significant changes in the phototaxis index at 3 h were 4.59 mg/L for glyphosate and 14.20 mg/L for cyhalofop-butyl;these concentrations corresponded to 0.06％ and 7.10％ of the field dosage,respectively.These results showed that glyphosate and cyhalofop-butyl are very toxic to daphnia.Therefore,their effects on the aquatic food chain should not be ignored.Changes in the phototaxis of D.carinata in response to herbicides at low concentrations may serve as an index of herbicide bio-toxicity in fresh water.