江湖水量交换对石臼湖藻类群体化聚集与小型化演替的影响

Field investigation organized by World Wide Fund for Nature (WWF) found that Shijiu Lake is one of the three lakes directly linked to Yangtze river in its middle and lower reaches. Shijiu Lake had been selected in Asian wetland directory and provincial nature reserve, with important ecological value and social significance. Under the influence of the Yangtze River and water exchange between river and lake, water levels and qualities of Shijiu Lake performed periodical changes, eutrophic tendency in dry season provided the greatest chance for algal colony aggregation and miniaturizing succession. Nowadays, in this lake picophytoplankton (0.2-2μm) concentration is fairly high, cyanobacterial colony particles are found in local regions, some measures are needed to prevent and control risks of water blooms. The forthcoming project of water source and storage engineering will further increase the necessity and urgency of algal research in Shijiu Lake. In the present study, process of algal colony aggregation and miniaturizing succession will be qualitative and quantitative expressed by means of laser particle analyzer, flow cytometry, and molecular biotechnology. Contribution of different environmental factors to variation of phytoplankton community structure will be investigated by multivariate statistical analysis according to measured data and mathematical models, so as to explore algae ecological effects of water exchange between Yangtze river and Shijiu Lake, and perform early warning for harmful algae. This study could provide scientific basis for environment protection of Shijiu Lake and could put forward reasonable evaluation for hydraulic engineering. Moreover, it will provide references for the research on ecological impacts of relationship between river and lake.

世界自然基金会（WWF）主办的野外调查发现石臼湖是长江中下游仅存的3个自然通江湖泊之一，该湖已入选亚洲湿地名录和省级自然保护区，具有重要的生态价值和社会意义。在长江水位和江湖水量交换的影响下，石臼湖水位和水质均出现周期性变化，枯水期的富营养化趋势为藻类群体化聚集和小型化演替提供了极大可能。目前石臼湖超微藻（0.2-2μm）浓度较高，局部出现蓝藻群体颗粒，亟需防控水华风险。计划建设的水源地和蓄水工程进一步增加了石臼湖藻类研究的必要性和紧迫性。本项目借助激光粒度仪、流式细胞仪以及分子生物学技术对石臼湖藻类群体化聚集与小型化演替过程进行定性和定量表征，通过实测数据和数理模型进行多元统计分析，揭示各个环境因子对藻类群落结构变化的贡献率，探明江湖水量交换的藻类生态效应，对有害藻类进行预警，为石臼湖水环境保护和水利工程的合理评价提供科学依据，为江湖关系的生态影响研究提供借鉴。

在长江水位和江湖水量交换的影响下，石臼湖水位和水质均出现周期性变化，枯水期的富营养化趋势为藻类群体化聚集和小型化演替提供了极大可能。石臼湖超微藻(0.2-2μm)浓度较高(5千万~80亿 cells/mL)，局部出现微囊藻群体颗粒(D50为100~800微米)，亟需防控水华风险。本研究发现夏季的磷浓度升高有利于微囊藻大群体形成，而氮浓度升高促进微囊藻生物量增加(Harmful Algae 2018,72:14-24.)。在藻类小型化演替方面发现氨氮有利于超微蓝藻生长，而硝氮促进微囊藻生物量累积(Tan et al. 2019 in press)。在微囊藻生长及防控过程中可以采用S-OD440来表征细胞完整性及其衰亡破裂比例(ES&T 2018, 52: 3295-3303)。本研究还发现低磷浓度(<0.01mg/L)有利于聚球藻，高磷浓度(>0.05mg/L)有利于微囊藻(https://doi.org/10.1007/s00128-018-2527-x)。本研究为探明微藻与超微藻演替规律，通江湖泊环境保护提供参考和借鉴。