两座亚热带水库真核浮游生物群落变化与构建机制

Community dynamics and assembly mechanisms of eukaryotic plankton in two subtropical reservoirs

摘要:

【目的】 真核浮游生物是水库生态系统的关键组分，在食物网中发挥承上启下的生态作用。本研究以两座亚热带深水水库(石兜水库和汀溪水库)为研究区，探究水库不同粒径范围(0.2–200μm、0.2–3 μm和3–200 μm)真核浮游生物群落的构建机制。【方法】 2015−2018年，对两座水库进行连续4年的季节采样，基于18S rRNA基因的V9可变区扩增测序和多元统计方法，研究水库不同粒径范围的真核浮游生物群落动态变化特征。【结果】 总体上，两座水库总真核浮游生物(0.2–200μm)与微型真核浮游生物(3–200 μm)优势门类变化的相关性较强，与微微型真核浮游生物(0.2–3μm)优势门类变化的相关性较弱。物种更替是驱动两座水库真核浮游生物群落时间动态变化的主要因素；2016年和2017年石兜水库更替物种总序列数均高于汀溪水库，而2018年则相反。与汀溪水库相比，石兜水库微微型真核浮游生物群落构建受确定性过程的影响比例更大。蓝藻叶绿素a浓度与汀溪水库真核浮游生物群落相关性较弱且不显著，而与石兜水库真核浮游生物群落显著相关，其中与石兜水库微微型真核浮游生物群落相关性最高。【结论】 微微型真核浮游生物群落比微型真核浮游生物群落更容易受蓝藻生物量影响；微型真核浮游生物群落变化一定程度上决定着总真核浮游生物群落的动态变化。全球变化背景下，应对不同粒径范围真核浮游生物进行监测，深入分析群落结构和功能变化，从而更好地保障水库生态健康和水质安全。

Abstract:

[Objective] Eukaryotic plankton are key components of a freshwater ecosystem, playing an important role in the food web. This study aims to explore the community dynamics and assembly mechanisms of three differently size-fractionated eukaryotic plankton communities (0.2–200, 0.2–3, and 3–200 μm) in two deep subtropical reservoirs (Shidou Reservoir and Tingxi Reservoir) in Xiamen. [Methods] From 2015 to 2018, samples were collected from both reservoirs in four seasons. The V9 region of eukaryotic 18S rRNA gene was amplified and sequenced to investigate the dynamic changes of eukaryotic plankton communities in the reservoirs. [Results] Overall, the temporal dynamics of dominant phyla of total eukaryotic plankton (0.2–200 μm) showed a strong correlation with that of micro-eukaryotic plankton (3–200 μm) and a weak correlation with that of pico-eukaryotic plankton (0.2–3 μm). Turnover was the main factor driving the temporal dynamics of eukaryotic plankton community composition in the two reservoirs. The proportions of the total number of sequences of the turnover species were higher in Shidou Reservoir than in Tingxi Reservoir in 2016 and 2017, while the opposite pattern was observed in 2018. Deterministic processes played a stronger role in the pico-eukaryotic plankton community assembly in Shidou Reservoir than in Tingxi Reservoir. The concentration of cyanobacterial chlorophyll a was weakly correlated with the eukaryotic plankton community in Tingxi Reservoir, while it was significantly correlated with the eukaryotic plankton community (especially the pico-eukaryotic plankton community) in Shidou Reservoir. [Conclusion] The pico-eukaryotic plankton community was more sensitive to cyanobacterial biomass than the micro-eukaryotic plankton community. The dynamics of the micro-eukaryotic plankton community largely determined the dynamics of the total eukaryotic plankton community. In the context of global changes, efforts should be made to monitor differently size-fractionated eukaryotic plankton and analyze the dynamics of community structure and functions for better understanding and protection of the reservoir ecosystem health and water quality.