Abstract：
Nutrient proportion, light intensity, and temperature affect the succession of dominant phytoplankton species. Despite these insights, this transformation mechanism in highly turbid lakes remains a research gap, especially in response to climate change. To fill this gap, we investigated the mechanism by which multi-environmental factors influence the succession of dominant phytoplankton species in Lake Chagan. This investigation deployed the structural equation model (SEM) and the hydrodynamic-water quality-water ecology mechanism model. Results demonstrated that the dominant phytoplankton species in Lake Chagan transformed from diatom to cyanobacteria during 2012 and 2022. Notably, Microcystis was detected in 2022. SEM revealed the primary environment variables for this succession, including water temperature (Tw), nutrients (total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH4N)), and total suspended solids (TSS). Moreover, this event was not the consequence of zooplankton grazing. An integrated hydrodynamic-water quality-bloom mechanism model was built to explore the mechanism driving phytoplankton succession and its response to climate change. Nutrients determined the phytoplankton biomass and dominant species succession based on various proportions. High NH4N:NO3N ratios favored cyanobacteria and inhibited diatom under high TSS. Additionally, the biomass proportions of diatom (30.77 % vs. 22.28 %) and green (30.56 % vs. 23.30 %) decreased dramatically. In contrast, cyanobacteria abundance remarkably increased (35.78 % to 51.71 %) with the increasing NH4-N:NO3-N ratios. In addition, the proportion of non-nitrogen-fixing cyanobacteria was higher than that of the nitrogen-fixing cyanobacteria counterparts when TN:TP≥20 and NH4N:NO3N ≥ 10. Light-limitation phenotypes also experienced an increase with the rising NH4N:NO3N ratios. Notably, the cyanobacterial biomass reached 3-6 times that in the baseline scenario when the air temperature escalated by 3.0 °C until 2061 under the SSP585 scenario. We highlighted the effect of nitrogen forms on the succession of dominant phytoplankton species. Climate warming will increase nitrogen proportion, providing an insightful reference for controlling cyanobacterial blooms.
摘要：
营养比例，光强度,温度影响浮游植物优势物种的演替。尽管有这些见解,这种在高浑浊湖泊中的转化机制仍然是一个研究空白，特别是在应对气候变化方面。为了填补这个空白，我们研究了多种环境因素影响查干湖浮游植物优势物种演替的机理。本研究采用了结构方程模型（SEM）和水动力-水质-水生态机制模型。结果表明，2012年和2022年，查甘湖浮游植物的优势物种从硅藻转变为蓝藻。值得注意的是,2022年检测到微囊藻。SEM揭示了这种演替的主要环境变量，包括水温(Tw)，养分(总氮(TN)，总磷（TP），和氨氮(NH4N))，和总悬浮固体(TSS)。此外，这一事件不是浮游动物放牧的结果。建立了水动力-水质-水华综合机制模型，探讨了浮游植物演替的驱动机制及其对气候变化的响应。营养元素根据各种比例决定了浮游植物的生物量和优势物种的演替。在高TSS下，高NH4N：NO3N比率有利于蓝细菌并抑制硅藻。此外,硅藻的生物量比例(30.77%vs.22.28%）和绿色（30.56%与23.30%）大幅下降。相比之下,随着NH4-N：NO3-N比率的增加，蓝细菌的丰度显着增加（35.78％至51.71％）。此外,当TN：TP≥20和NH4N：NO3N≥10时，非固氮蓝藻的比例高于固氮蓝藻的比例。光限制表型也随着NH4N：NO3N比率的升高而增加。值得注意的是,在SSP585情景下，当空气温度升高3.0°C直到2061时，蓝细菌生物量达到基线情景的3-6倍。我们强调了氮形式对优势浮游植物物种演替的影响。气候变暖将增加氮的比例，为控制蓝藻水华提供了有见地的参考。
