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| The effect of cyanobacteria on dissolved organic carbon post the bloom in autumn in Western Lake Taihu |
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Abstract Surface water sample from western Lake Taihu was collected monthly from July 2009 to March 2010. Chlorophyll a, cyanobacterial cell lysis rate, phosphate concentration were analyzed. Meanwhile high molecular weight (1kDa~0.5μm) dissolved organic carbon was separated by cross-flow ultrafiltration, and its concentration as well as the carbon to nitrogen ratio were measured. The highest cyanobacterial cell lysis rate (0.43d-1) was observed in November, while the maximum phosphate and high molecular weight dissolved organic carbon concentration was observed in December and September, respectively. No significant relationships were concluded between cell lysis rate and phosphate concentration, as well as high molecular weight dissolved organic carbon concentration. Cyanobacterial cell lysis rate was one of the factors that affect the levels of phosphate and high molecular weight dissolved organic carbon. The surrounding phosphate level was contributed to the phosphorus fractions transformation between organic phosphorus and phosphate. High molecular weight dissolved organic carbon in lake could be associated with other factors such as wind-induced resuspension of sediments and the frequent activity of bacteria through the microbial carbon loop. Compared to the nitrogen compounds, the carbon compounds were easily degraded, which resulted the decrease of carbon to nitrogen ratio after the bloom. Furthermore, the decrease of carbon to nitrogen ratio could have also been due to an increase in dissolved organic nitrogen produced from nitrate by heterotrophic bacteria.
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Received: 01 June 2010
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