山东近海浮游植物群落对核电站温排水热效应的响应机制研究

Haiyang nuclear power plant and Shidao Bay nuclear power plant are under construction on the coast of Shandong Province. Thermal effluent from the nuclear power plant can elevate the water temperature in nearby coastal waters. As a result, the species composition and cell abundance of phytoplankton will change, thus the structure and function of ecosystem will change as well. Study on the response of phytoplankton community to the temperature elevation will facilitate our understanding of the environmental effects of two nuclear power plants. In this study, we propose to investigate the seasonal and spatial variations of phytoplankton community structure by microscopic observation, flow cytometric method and high-throughput sequencing. Field incubation experiments under temperature elevation, including microcosm experiments and dilution experiments, will be carried out to monitor the succession of phytoplankton community and estimate the growth rate and grazing mortality rate of phytoplankton. Furthermore, the key species of phytoplankton are planned to be incubated under different temperature and the biochemical compositions and physiological metabolism activities will be assessed to clarify the response to temperature elevation. Overall, the outcome of this project is aimed to predict the change of phytoplankton community affected by nuclear power plant thermal effluent, and figure out the effects of temperature elevation on different phytoplankton groups and species. This research will be also helpful to assess the risk of algal blooms and to establish the prior-warning mechanism.

海阳核电站和石岛湾核电站即将建成投产，运行后将产生大量温排水。温排水的热效应可改变受纳海域浮游植物的物种组成和细胞丰度，进而影响近海生态系统的结构和功能。因此，研究海阳和荣成近海水域浮游植物群落对温排水热效应的响应机制，有助于全面认识两座核电站运行后的环境效应。本项目拟采用显微镜检法、流式细胞仪技术和高通量测序技术研究调查海域的浮游植物群落结构及其时空分布特征；开展现场增温实验，通过小尺度围隔实验监测温升影响下浮游植物群落的演替，通过稀释法实验比较不同增温幅度下浮游植物不同类群的生长率和摄食死亡率；分离纯化浮游植物关键种，分析其生理生化指标在不同温度条件下的变化，研究浮游植物关键种对温升的响应机制。以期预测核电站温排水可能引发的浮游植物群落结构的改变；探明温升对不同浮游植物类群和物种的影响；评估增温条件下藻华爆发的风险，为建立藻华预警机制提供基础资料。

本项目通过现场调查、船基培养和室内实验，综合运用显微镜检法、流式细胞仪技术和高通量测序技术研究了山东近海浮游植物群落对核电站温排水热效应的响应机制。基于渤黄海季度调查、胶州湾周年逐月调查和荣成近海季度调查，获得了翔实的山东近海典型海区浮游植物数据，掌握了浮游植物群落的结构特点和动态变化规律；在渤黄海近岸站位开展船基培养实验，利用稀释法估算了不同培养温度下浮游植物群落的生长率和摄食死亡率，分析了温升对近海浮游植物群落生长和死亡的影响；在荣成近海站位开展船基围隔培养实验，观测了不同培养温度下叶绿素a浓度、微微型浮游植物丰度、浮游植物群落组成的变化，研究了浮游植物群落演替对温升的响应。研究发现渤海、北黄海近岸海域浮游植物存在很高的多样性，除了硅藻和甲藻，隐藻、绿藻、定鞭藻、硅鞭藻和金藻等浮游植物类群也贡献了较高的多样性；异孢藻、卡尔藻等裸露的甲藻以及寄生性甲藻阿米巴藻在群落中有较高的占比；葡萄藻、微单胞藻、Ostreococcus藻等微小型浮游植物在山东近海也有分布。在温度较低的季节增温能升高浮游植物群落的内禀生长率和摄食死亡率，而在高温季节则会降低二者。增温会加快浮游植物的生长，使生物量高峰提前1~2天出现；在春季，增温能促使浮游植物达到更高的生物量；而在夏季，增温会降低浮游植物生物量的峰值。在门（纲）水平上，增温对甲藻和绿藻的群落占比没有明显影响，有利于硅藻群落占比的增加，但不利于隐藻群落占比的增加。在属的水平上，春季促进硅鞭藻（属）的生长，抑制Telonema藻的生长；夏季促进角毛藻的生长。本研究的开展有助于全面认识核电站温排水对近海生态环境的影响，为建立核电站冷源水域藻华预警机制、保障核电站安全运行提供有效技术支撑；有助于深入了解近海浮游植物群落对全球变暖的响应机制，对提升我国近海生态系统相关研究有积极意义。