Seasonal dynamics of water bloom-forming Microcystis morphospecies and the associated extracellular microcystin concentrations in large, shallow, eutrophic Dianchi Lake
Wu Yan-Long
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Song Li-rong
DOI:
Received November 05, 2013,Revised December 26, 2013, Accepted December 31, 2013, Available online 2014-04-09
Volume ,,Pages -
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The increasing occurrence of Microcystis blooms is of great concern to public health and ecosystem due to the potential hepatotoxic microcystins (MCs) produced by these colonial cyanobacteria. In order to interpret the relationships between variations of Microcystis morphospecies and extracellular MCs concentrations, the seasonal dynamics of phytoplankton community composition, MCs concentrations, and environmental parameters were monitored monthly from August, 2009 to July, 2010. The results indicated that Microcystis dominated total phytoplankton abundance from May to December (96–99% of total biovolume), with toxic M. viridis and non-toxic M. wesenbergii dominated after July (constituting 65-95% of the Microcystis population), followed by M. viridis as the sole dominant species from November to January (49.0–93.2%). Correlation analysis revealed that water temperature and nutrient were the most important variables accounting for the occurrence of M. wesenbergii, while the dominance of M. viridis was related with nitrite and nitrate. The relatively low content of MCs was explained by the association with a large proportion of M. viridis and M. wesenbergii, small colony size of Microcystis populations, and low water temperature, pH and dissolved oxygen. The extracellular MC (mean of 0.477±0.204 μg/L) of water samples analyzed by ELISA demonstrated the low concentrations of microcystin in Dianchi Lake which implied the low potential risk for human health in the basin. The survey provides the first whole-lake study of the occurrence and seasonal variability of Microcystis population and extracellular MCs that are of particular interest for water quality monitoring and management.
