淡水水体中水华的暴发对水环境造成严重危害，营养盐对形成水华起着重要的作用。为探究水华暴发期营养盐对藻类生长的影响程度，以三峡水库的支流澎溪河原生藻类群落为实验对象，利用自主设计的原位装置开展原位受控实验。在装置内进行了磷、高氮和低氮3种实验，装置内的其他生境条件与周围的环境保持一致。研究发现：在磷实验和低氮实验过程中，叶绿素呈下降趋势，而在高氮实验中叶绿素呈上升趋势。为明确不同实验条件下叶绿素变化趋势不一致的原因，通过化学计量学、相关性分析及非线性拟合等方法，对形成不同叶绿素趋势的原因进行了分析研究，结果表明：水华暴发期澎溪河藻类生长的最适N：P为32.52，且澎溪河藻类生长的最适总磷和总氮浓度分别为0.12、2.44 mg/L；营养盐和水温是原位条件下藻类生长的主要影响因素，营养盐浓度过高（总氮浓度高于2.44 mg/L）、营养盐浓度过低（低于化学计量学上藻类所需要最低营养盐浓度）、水温过低（低于20℃）均会抑制藻类的生长，且与营养盐浓度过高相比，水温过低/营养盐浓度过低对藻类生长抑制作用较强；水华的暴发需要同时满足营养盐条件（营养盐浓度需大于藻类在化学计量学上所需要的最低浓度）和温度条件（水温高于20℃）。

Algae blooming in freshwater severely damages the aquatic ecosystem seriously, and nutrient level is the key environmental factor that results in the formation of algae blooming. For purpose of revealing the influence degrees of nutrient on the in situ growth of algae during the algae blooming, this study took the algae assemblages as the research object, and self designed devices were used in in situ experiments, which were carried out in the Pengxi River of the Three Gorges Reservoir. In this study, three different treatments including phosphorus, high nitrogen and low nitrogen treatments were introduced, and the conditions in the devices were consistent with that in the nature water body. During the phosphorus treatment as well as low nitrogen treatment, chlorophyll a showed a dramatic decreasing trend but did not manifest the same trend during the high nitrogen treatment. In order to elucidate the reason that caused the different chlorophyll a trend during different treatments, there were several methods conducted in this study to analyse and study the causes of different chlorophyll trends, such as chemometrics and correlation analysis, besides non-linear fitting. Finally, the results showed:(1) The optimal N:P for algae growth in the Pengxi River was 32.52, and the suitable phosphorus and nitrogen concentration for algae growth were 0.12 mg/L and 2.44 mg/L, respectively; (2) Both nutrient and water temperature were the key factors that resulted in the in situ algae growth. High nutrient concentration (the concentration of nitrogen was higher than 2.44 mg/L), low nutrient concentration (lower than the concentration that algae required for chemometrics), and low water temperature (lower than 20℃) might inhibit the algae growth. In contrast to the high nutrient concentration, the low nutrient concentration or the low water temperature could bring out higher inhibition for algae growth; (3) Algae blooming in the Pengxi River must meet two premises:Sufficient nutrient (higher than the lowest nutrient concentration that algae required for chemometrics) and appropriate suitable water temperature (higher than 20℃).

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国家自然科学基金（41771520）；国家重点研发计划（2019YFD1100501）