title: Ecotoxicity of two organophosphate pesticides chlorpyrifos and dichlorvos on non-targeting cyanobacteria Microcystis wesenbergii.
abstract: Organophosphate pesticides (OPs), as a replacement for the organochlorine pesticides, are generally considered non-toxic to plants and algae. Chlorpyrifos and dichlorvos are two OPs used for pest control all over the world. In this study, the dose-response of cyanobacteria Microcystis wesenbergii on OPs exposure and the stimulating effect of OPs with and without phosphorus source were investigated. The results showed that high concentrations of chlorpyrifos and dichlorvos caused significant decrease of chlorophyll a content. The median inhibitory concentrations (EC50) of chlorpyrifos and dichlorvos at 96 h were 15.40 and 261.16 μmol L(-1), respectively. Growth of M. wesenbergii under low concentration of OPs (ranged from 1/10,000 to 1/20 EC50), was increased by 35.85 % (chlorpyrifos) and 41.83 % (dichlorvos) at 120 h, respectively. Correspondingly, the highest enhancement on the maximum quantum yield (F v/F m) was 4.20 % (24 h) and 9.70 % (48 h), respectively. Chlorophyll fluorescence kinetics, known as O-J-I-P transients, showed significant enhancements in the O-J, J-I, and I-P transients under low concentrations of dichlorvos at 144 h, while enhancements of chlorophyll fluorescence kinetics induced by low concentrations of chlorpyrifos were only observed in the J-I transient at 144 h. Significant decreases of chlorophyll content, F v/F m and O-J-I-P transients with OPs as sole phosphorus source were found when they were compared with inorganic phosphate treatments. The results demonstrated an evidently hormetic dose-response of M. wesenbergii to both chlorpyrifos and dichlorvos, where high dose (far beyond environmental concentrations) exposure caused growth inhibition and low dose exposure induced enhancement on physiological processes. The stimulating effect of two OPs on growth of M. wesenbergii was negligible under phosphate limitation.
authors: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
authors: Kai-Feng
authors: KF
authors: Sun
authors: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China. xuxr@scsio.ac.cn.
authors: Xiang-Rong
authors: XR
authors: Xu
authors: Department of Ecology, Jinan University, Guangzhou, 510632, China.
authors: Shun-Shan
authors: SS
authors: Duan
authors: State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
authors: You-Shao
authors: YS
authors: Wang
authors: State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
authors: Hao
authors: H
authors: Cheng
authors: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
authors: Zai-Wang
authors: ZW
authors: Zhang
authors: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
authors: Guang-Jie
authors: GJ
authors: Zhou
authors: State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
authors: Yi-Guo
authors: YG
authors: Hong
mesh_terms: D001673:Biodegradation, Environmental; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D004390:Chlorpyrifos / Q000633:toxicity*; D004006:Dichlorvos / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005453:Fluorescence; D059165:Hormesis; D007306:Insecticides / Q000633:toxicity*; D007700:Kinetics; D046931:Microcystis / Q000187:drug effects* / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D007306:Insecticides; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D004006:Dichlorvos; D004390:Chlorpyrifos; D000077194:Chlorophyll A
keywords: Chlorophyll fluorescence; Chlorpyrifos; Dichlorvos; Hormesis; M. wesenbergii