Anthropogenic regulation of hydrographs is a widespread approach to river management; however, the effects of river regulation on habitat conditions and aquatic communities have rarely been studied. In this study, we analyzed the physical, chemical, and biological data from the lower Nakdong River in South Korea from 2005 to 2009 before weir construction and from 2012 to 2016 after weir construction. A partial least square path model (PLS-PM) was applied to delineate the complex interrelationships of diatoms and cyanobacteria with physicochemical parameters, nutrients, zooplankton grazing, and hydrological parameters. Inferential modeling using the hybrid evolutionary algorithm (HEA) allowed the identification of differences in the importance and threshold conditions of population dynamics drivers of diatoms and cyanobacteria before and after flow regulation. The annually averaged trajectories of limnological variables displayed significant shifts in seasonality and magnitudes of phytoplankton, zooplankton, and nutrient concentrations between the two periods. The results of PLS-PM indicated that, after flow regulation, diatoms and cyanobacteria were directly affected by nutrients and zooplankton densities and the path coefficients of hydrological parameters decreased or even were insignificant. The inferential models suggested that diatom dynamics were essentially shaped by threshold conditions of water temperature (WT) and pH before regulation, but mainly by those of rotifers (below 51.1 ind. L⁻¹) after regulation. As for cyanobacteria dynamics, WT was identified as a critical threshold condition before and after regulation, and the threshold of PO₄⁻ concentration above 145.4 L⁻¹ was identified as the reason for occasional blooms during the post-regulation period. Overall, the results suggest that flow regulation gradually alters habitat conditions typically of rivers to those of stagnant waters. These findings must be taken into account for sustainable management strategies of regulated rivers.

人为调节水文过程线是河流管理的一种普遍方法；然而，很少研究河流调节对栖息地条件和水生群落的影响。在这项研究中，我们分析了韩国洛东江下游 2005 年至 2009 年建堰前和 2012 年至 2016 年建堰后的物理、化学和生物数据。应用偏最小二乘路径模型 (PLS-PM) 来描绘硅藻和蓝藻与物理化学参数、营养物质、浮游动物放牧和水文参数之间的复杂相互关系。使用混合进化算法 (HEA) 的推理建模允许识别流量调节前后硅藻和蓝藻种群动态驱动因素的重要性和阈值条件的差异。湖沼学变量的年平均轨迹显示了两个时期之间浮游植物、浮游动物和养分浓度的季节性和量级的显着变化。PLS-PM结果表明，流量调节后，硅藻和蓝藻直接受养分和浮游动物密度的影响，水文参数的路径系数降低甚至不显着。推论模型表明，硅藻动力学主要受调节前水温 (WT) 和 pH 值的阈值条件影响，⁻¹ ) 调节后。至于蓝藻动态，WT被确定为调控前后的临界阈值条件，PO ₄ ^-浓度高于145.4 L ^-1的阈值被确定为调控后期间偶尔开花的原因。总体而言，结果表明流量调节逐渐将河流的栖息地条件改变为停滞水域的栖息地条件。这些发现必须考虑到受管制河流的可持续管理策略。