Microcystis Bloom in an Urban Lake after River Water Diversion—A Case Study

Xiaoyan Chen,Yiyong Zhou,Dong Bai,Chunlei Song,Xiuyun Cao

doi:10.3390/w12061811

Xiaoyan Chen, Yiyong Zhou + Show 3 more

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https://doi.org/10.3390/w12061811

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Abstract

To improve the water quality of Lake Yuehu, a water diversion from the Han River was conducted in July 2008. However, an unexpected Microcystis bloom occurred in the lake after water introduction. Water and sediment samples were collected from Lake Yuehu and the variation of chemical and biochemical parameters, as well as the phytoplankton community, were analyzed during the water diversion to assess its effect and to clarify the mechanism leading to the Microcystis bloom. The nitrogen (N) concentration was increased and phosphorus (P) concentration decreased in Lake Yuehu after receiving water from the Han River, which had a high loading of N and a low loading of P. These conditions may benefit the growth and dominance of non-N2 fixing Microcystis, as it may not have suffered from P limitation during our study because it did not produce extracellular phosphatase, which worked as an indicator of P deficiency, as evidenced by the in situ enzyme-labelled fluorescence. Notably, the sediment Fe (OOH)~P content significantly decreased in Lake Yuehu; this pulsed release of P from the sediment might have sustained the Microcystis bloom. Based on our results, algal blooms may occur as a consequence of conducting water diversion projects to improve water quality.

Highlights

Eutrophication and cyanobacterial blooms caused by genera such as Microcystis have become increasingly common in freshwater ecosystems globally, especially in urban lakes, resulting in a serious threat to recreational functions [1,2,3]
NO3-N was the main component of the Dissolved inorganic of N (DIN) in all sampling sites, four times higher than Lake Yuehu (Figure 2a)
We proposed that the transformation of nutrients in Lake Yuehu due to water diversion have might triggered the Microcystis bloom, since no annual Microcystis bloom was observed before the water diversion at the same season with similar meteorological conditions

Summary

Introduction

Eutrophication and cyanobacterial blooms caused by genera such as Microcystis have become increasingly common in freshwater ecosystems globally, especially in urban lakes, resulting in a serious threat to recreational functions [1,2,3]. Most Microcystis strains have been demonstrated to produce potent hepatatoxin microcystin, blooms of which would threaten human health, recreational activities and fisheries. Diverting water from rivers to lakes is one of the approaches that targets a reduction in the incidence of blooms or eutrophication in lakes. It is unclear whether water diversion could improve water quality, and little is known about the influence mechanism of water diversion on blooms of Microcystis in lakes

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