Mechanism study on the frequent variations of cell-bound microcystins in cyanobacterial blooms in Lake Taihu: Implications for water quality monitoring and assessments

Cyanobacteria-/cyanotoxin-contaminations and eutrophication status before Wuxi Drinking Water Crisis in Lake Taihu, China

“…As a result, the concentrations of determined intracellular toxins would be correspondingly lower than that in cool seasons. Our results were consistent with the studies after the crisis (Song et al, 2007;Chen et al, 2009), but somewhat different from the previous investigation by Shen et al (2003). In their study, high temperature would increase the concentrations of cellbound toxins, and the maximum toxin production for the blooms occurred in Aug and Sep.…”

“…4 indicated that the concentrations of intracellular toxins changed with sampling sites and sampling months quickly, even there was no big difference between the bloom biomass in the water columns. Similar results were also obtained in studies after the water crisis (Song et al, 2007;Chen et al, 2009), in which the quick variations of MCs concentrations were related with the changes of different Microcystis colonies. In the present study, the concentrations of intracellular toxins in May, Aug and Sep were significantly lower than that in Jun, Jul and Oct.…”

“…In this study, the similar results were obtained, and no obvious correlations was found between the production of each toxin variants, together with the total toxins and the nutrient levels in Lake Taihu (Table 2). Results from the present study were somewhat different from that of Chen et al (2009) who reported that toxin concentration was negatively correlated not only with N:P ratio, but also with the TN contents. In our study, similar correlations were only observed between the concentrations of total intracellular MCs and the N:P ratios.…”

“…As to the functions of nutrients in the course of the toxin synthesis in toxic cyanobacteria, there were several explanations. Some studies proposed that high phosphate concentration did not seem to enhance the toxic colonies or toxin concentrations in natural blooms from field studies (Chen et al, 2009;Briand et al, 2009). However, some other laboratory studies investigated toxinproducing abilities by using toxic and nontoxic Microcystis strains, suggesting that phosphate concentrations were beneficial to the growth of toxic strains but detrimental to nontoxic strains (Vézie et al, 2002).…”

Seasonal dynamics of water bloom-forming Microcystis morphospecies and the associated extracellular microcystin concentrations in large, shallow, eutrophic Dianchi Lake

“…The study of Chen et al (2009) had shown that the frequent variations of MCs in both concentrations and toxin species were associated with the frequent alteration of Microcystis colonies or/and species from the monitoring results of Microcystis colonies in Taihu Lake. High concentration of MCs in the blooms was always associated with M. flos-aquae and M. aeruginosa, whereas when M. wesenbergii was the dominant colonial type, the MC production was low.…”