Abstract
Cyanobacterial blooms caused by eutrophication in Lake Taihu have led to ecological threats to freshwater ecosystems. A pilot scale experiment was implemented to investigate the relationship between cyanobacteria and other aquatic plants and animals in simulated eutrophic ecosystems under different phosphorus (P) regimes. The results of this study showed that cyanobacteria had two characteristics favorable for bloom formation in eutrophic ecosystems. One is the nutrient absorption. The presence of alkaline phosphatase was beneficial for algal cells in nutrition absorption under low P concentration. Cyanobacteria exhibited a stronger ability to absorb and store P compared to Vallisneria natans, which contributed to the fast growth of algal cells between 0.2 and 0.5 mg·L−1 of P (p < 0.05). However, P loads affected only the maximum biomass, but not the growth phases. The growth cycle of cyanobacteria remained unchanged and was not related to P concentration. P cycling indicated that 43.05–69.90% of the total P existed in the form of sediment, and P content of cyanobacteria showed the highest increase among the organisms. The other is the release of microcystin. Toxic microcystin-LR was released into the water, causing indirectly the growth inhibition of Carassius auratus and Bellamya quadrata and the reduction of microbial diversity. These findings are of importance in exploring the mechanism of cyanobacterial bloom formation and the nutrient management of eutrophic lakes.
Highlights
Lake Taihu is the third largest freshwater lake in China and is located in one of the most developed and densely populated regions in the country
Was released into the water, causing indirectly the growth inhibition of Carassius auratus and Bellamya quadrata and the reduction of microbial diversity. These findings are of importance in exploring the mechanism of cyanobacterial bloom formation and the nutrient management of eutrophic lakes
Microcystis aeruginosa (FACHB-912) isolated from the cyanobacterial bloom in 2007 in Lake Taihu were used in this study, which was purchased from the Institute of Hydrobiology, Chinese Academy of Sciences (Wuhan, China)
Summary
Lake Taihu is the third largest freshwater lake in China and is located in one of the most developed and densely populated regions in the country. Lake Taihu is rich in fisheries resources, with common species including Coilia mystus, Cyprinus carpio, and Carassius auratus [1]. Several submerged macrophytes exist in Lake Taihu, dominated by Potamogeton wrightii Morong, Vallisneria natans, and Hydrilla verticillata [2]. The area has experienced significant deterioration in recent decades as a result of urbanization and agricultural expansion, increased nutrient inputs from domestic wastes, industrial discharge, and fertilizer use. This eutrophication transformed Lake Taihu into a cyanobacteria-dominated system, with blooms occurring regularly from April to November throughout the lake
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