The dynamics of toxic and nontoxic Microcystis during bloom in the large shallow lake, Lake Taihu, China

Abstract

Lake Taihu is a large shallow freshwater lake (surface area 2,338 km(2), mean depth 1.9 m) in China, which has experienced toxic cyanobacterial bloom dominated by Microcystis annually during the last few decades. In the present study, the dynamics of toxic and nontoxic Microcystis in three sampling stations (Meiliang Bay (site N2), Gonghu Bay (site N4), and the lake center area (site S4)) were quantified using quantitative real-time PCR (qPCR) during bloom periods from April to September, 2010. Our data showed that the abundance of toxic Microcystis and the toxic proportion gradually increased from April to August in water samples and reached the peak in August. During the study period, toxic Microcystis genotypes comprised between 26.2 and 64.3, between 4.4 and 22.1, and between 10.4 and 20.6 % of the total Microcystis populations in the three sampling sites, respectively. Correlation analysis suggested that there was a strong positive relationship between total Microcystis, toxic Microcystis and the toxic proportion. Chlorophyll a, total phosphorus, and water temperature were positively correlated with the abundances of total Microcystis and toxic Microcystis. Furthermore, the toxic proportion was positively correlated with total phosphorus (P < 0.05) and water temperature (P < 0.01), showing that global warming together with eutrophication could promote more frequent toxic blooms.

Distribution of the Harmful Bloom-Forming Cyanobacterium, <i>Microcystis aeruginosa</i>, in 88 Freshwater Environments across Japan

“…On the other hand, low-nutrient conditions, which were defined as concentrations of less than 400 μg L -1 for TN and/or 20 μg L -1 for TP (Fujimoto et al, 1997), were observed at 18 sites, and these sites also showed low Microcystis abundance (2.0×10 2 to 1.8×10 4 copies mL -1 of the IGS-PC gene) or levels below the detection limit. Although TN and/or TP have been shown to correlate with toxic cyanobacteria abundance (Vézie et al, 2002;Davis et al, 2009;Li et al, 2014b), it is important to note that Microcystis itself contributes to TN, TP, and TOC concentrations. Although the present results showed no correlation between the index of mcyA/PC and environmental factors, the gene abundance of mcyA and IGS-PC positively correlated in a log-log scale comparison (R 2 =0.91, Fig.…”

Responses of phytoplankton functional groups to simulated winter warming

“…Slim et al (2014) suggested that blooms of cyanobacteria, specifically M. aeruginosa and Aphanizomenon ovalisporum caused by warming could also disturb the ecosystem and the functioning of the Lake Karaoun, Lebanon. Furthermore, Joung et al (2011) and Gkelis et al (2014) suggested that high temperature would promote the growth of MC-producing genotypes and Li et al (2014) also indicated that global warming could promote more frequent toxic blooms in Lake Taihu, China. The increased microcystin produced by Microcystis would have accelerating negative effects on lake ecosystem structure and ecosystem.…”

Local nutrient regimes determine site-specific environmental triggers of cyanobacterial and microcystin variability in urban lakes

“…Past studies have found large variations in the percentage of potentially toxic cyanobacteria and in the microcystin concentration between spatially isolated phytoplankton communities (Sitoki et al, 2012;Li et al, 2014). Furthermore, it was reported that the variability of cyanobacterial biomass in lakes only explained a small fraction of the variability in microcystin concentration (Sinang et al, 2013;Eva and Lindsay, 2014).…”