Quantification of microcystin-producing and non-microcystin producing Microcystis populations during the 2009 and 2010 blooms in Lake Taihu using quantitative real-time PCR.
Lake Taihu, a large, shallow hypertrophic freshwater lake in eastern China, has experienced lake-wide toxic cyanobacterial blooms annually during summer season in the past decades. Spatial changes in the abundance of hepatotoxin microcystin-producing and nonmicrocystin producing Microcystis populations were investigated in the lake in August of 2009 and 2010. To monitor the densities of the total Microcystis population and the potential microcystin-producing subpopulation, we used a quantitative real-time PCR assay targeting the phycocyanin intergenic spacer (PC-IGS) and the microcystin synthetase gene (mcyD), respectively. On the basis of quantification by real-time PCR analysis, the abundance of potential toxic Microcystis genotypes and the ratio of the mcyD subpopulation to the total Microcystis varied significantly, from 4.08 x 10(4) to 5.22 x 10(7) copies/mL, from 5.7% to 65.8%, respectively. Correlation analysis showed a strong positive relationship between chlorophyll-a, toxic Microcystis and total Microcystis; the abundance of toxic Microcystis correlated positively with total phosphorus and ortho-phosphate concentrations, but negatively with TN:TP ratio and nitrate concentrations. Meanwhile the proportion of potential toxic genotypes within Microcystis population showed positive correlation with total phosphorus and ortho-phosphate concentrations. Our data suggest that increased phosphorus loading may be a significant factor promoting the occurrence of toxic Microcystis bloom in Lake Taihu.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences,Nanjing 210008, China. ldm8212@126.com
Daming
D
Li
Fanxiang
F
Kong
Xiaoli
X
Shi
Linlin
L
Ye
Yang
Y
Yu
Zhen
Z
Yang
D002681:China; D005838:Genotype; D057097:Harmful Algal Bloom; D060106:Lakes; D052998:Microcystins / Q000096:biosynthesis*; D046931:Microcystis / Q000235:genetics* / Q000254:growth & development; D016133:Polymerase Chain Reaction
D052998:Microcystins; C078588:microcystin