Daily and vertical dynamics of rotifers under the impact of diatom blooms in the Three Gorges Reservoir,China |
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Authors: | Shuchan Zhou Qinghua Cai Yaoyang Xu Xinqin Han |
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Institution: | (1) State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, People’s Republic of China; |
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Abstract: | The Three Gorges Dam was built in 2005 with a storage capacity of 39.3 billion m3, ranking 22nd in the world. However, since the impoundment of the reservoir, serious blooms of phytoplankton have occurred.
Rotifers, having a key role in the freshwater aquatic food web, are important grazers of phytoplankton and an essential food
resource to higher trophic consumers. To explore the impacts of phytoplankton blooms on the rotifer community, daily and vertical
surveys of rotifers were conducted in a bay of the Three Gorges Reservoir (Xiangxi Bay). Altogether 46 rotifer species were
registered, and Synchaeta tremula, Polyarthra vulgaris, and Brachionus calyciflorus were the most abundant species accounting for 36, 26, and 16% of the mean rotifer densities, respectively. Although these
dominant species always prevailed in the rotifer community, their proportions changed significantly from non-bloom phase to
bloom phase, e.g., the significance of S. tremula deceased from 46.8 to 33.2%, while P. vulgaris and B. calyciflorus increased from 23.9 and 13.9% to 26.2 and 16.2%, respectively. In the vertical water column, all the rotifer following phytoplankton
displayed an aggregated distribution, concentrating at the upper layers (0.5–5 m), especially during the bloom phase. From
the non-bloom phase to the bloom phase, rotifer densities, the dominant rotifers, Shannon–Wiener and Margalef’s diversity
increased significantly, while the evenness displayed the opposite trend. Non-metric multidimensional scaling analysis (NMDS)
revealed that the samples in the non-bloom phase were well separated from those in the bloom phase. This means that the outbreak
of the diatom bloom in the Xiangxi Bay had significant impacts on the rotifer community. Further investigations are needed
to address the impacts of the changes of rotifer community on higher trophic levels. |
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