title: Occurrence and spatial distributions of microcystins in Poyang Lake, the largest freshwater lake in China.
abstract: Occurrence and spatial distributions of microcystins (MCs; MC-RR, -YR, -LR, -LA, -LF, -LW) in Poyang Lake were studied during the period from July 6 to July 18, 2012, by using ultra-high-performance liquid chromatography-electrospray ionization tandem triple quadrupole/mass spectrometry (UPLC-MS/MS). MC-RR was the most dominant variant (94.70 and 84.73 % for intracellular (cellular MCs) and extracellular (dissolved MCs) MCs, respectively) in Poyang Lake, followed by MC-LR (4.65 and 13.17 %, respectively), MC-YR (0.8 and 2.63 %, respectively), and MC-LA (0.02 and 0.00 %), while MC-LW and MC-LF were not detected. Total MCs concentrations (intracellular +extracellular MCs) ranged between 0.0036 and 7.97 μg/L, with an average of 0.79 μg/L, and only two sampling stations with the total MCs concentrations exceeded the drinking water guideline level of 1 μg/L for MC-LR proposed by World Health Organization. The overall spatial pattern of intracellular and extracellular MCs in Poyang Lake demonstrates decreasing trends from east to west, and the south part higher than the north part. Intracellular MCs content was negatively correlated with total nitrogen (r = -0.34, p < 0.01) and NO3 (r = -0.35, p < 0.01), while no significant correlation was found between intracellular MCs concentration and total phosphorus, NH4, and NO2 (p > 0.05), suggesting that NO3 might be a regulating factor for MCs production in Poyang Lake. In addition, intracellular MCs concentrations were positively correlated with wind speed, Microcystis and Cyanobacteria biomass (r = 0.34-0.51, p < 0.05), indicating that wind speed plays an important role in the spatial distributions of MCs, and NO3, toxic cyanobacteria (mainly Microcystis), and wind speed seem to be the important forcing factors driving MCs spatial distributions in Poyang Lake.
authors.affiliation: Institute for Quality & Safety and Standards of Agricultural Products Research, Jiangxi Academy of Agricultural Sciences, Nanlian Road 602, Nanchang, 330200, Jiangxi, People's Republic of China.
authors.forename: Dawen
authors.initials: D
authors.lastname: Zhang
authors.forename: Qiegen
authors.initials: Q
authors.lastname: Liao
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Donggen
authors.initials: D
authors.lastname: Wang
authors.forename: Linguang
authors.initials: L
authors.lastname: Luo
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Chen
authors.forename: Jiayou
authors.initials: J
authors.lastname: Zhong
authors.forename: Jutao
authors.initials: J
authors.lastname: Liu
mesh_terms: D002681:China; D002853:Chromatography, Liquid; D060766:Drinking Water / Q000737:chemistry; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry; D060106:Lakes / Q000737:chemistry*; D052998:Microcystins / Q000032:analysis*; D010839:Phytoplankton / Q000145:classification / Q000302:isolation & purification; D062206:Spatial Analysis; D053719:Tandem Mass Spectrometry; D014873:Water Pollutants / Q000032:analysis*; D014919:Wind
chemical_list: D060766:Drinking Water; D052998:Microcystins; D014873:Water Pollutants; C078588:microcystin