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.

Responses of Water Level in China’s Largest Freshwater Lake to the Meteorological Drought Index (SPEI) in the Past Five Decades

“…The Poyang Lake Basin is one of the key areas of global water security and biodiversity conservation [23], and it is an important production base of grain, oil, cotton and aquatic products in China, feeding a population of up to 44 million [24,25]. The annual discharge from the Poyang Lake Basin is approximately 1457 × 10 8 m 3 , accounting for 5.3% of the national water resources and 15.7% of the discharge in the Yangtze River Basin [26].…”

Decadal Sedimentation in China's Largest Freshwater Lake, Poyang Lake

“…Poyang Lake, located in the middle stream of the Changjiang River, provides a habitat for approximately 44 million people (D. W. Zhang et al, ) as well as over 200 species of migratory waterfowl, including the special Siberian white crane ( Grus leucogeranus ; Jiao, ). Despite its vital socioeconomic and ecological significance, the depositional system of Poyang Lake has become more fragile since the beginning of the 21st century, with its surface area reduced by 226 km 2 between 1991 and 2010 (Q. Zhang, Li et al, ), while exposed wetland area in October increased by 1,078 km 2 from 1955 to 2012 (Mei et al, ).…”

The toxic effects of microcystin-LR on mouse lungs and alveolar type II epithelial cells

“…However, the concentrations of MCs in many water bodies are far beyond that guideline. One study showed that the level in the Poyang Lake, the largest freshwater lake in China, was 7.97 μg/L (Zhang et al, 2015), whereas in the Hoan Kiem Lake of northern Vietnam, a concentration of MCs as high as 46 μg/L was recorded (Duong et al, 2013). MC-LR is chemically stable and has a very slow natural degradation process.…”