Institut National de La Recherche Scientifique (INRS), Centre Eau Terre Environnement (ETE), 490 De La Couronne, Québec City, Québec, G1K 9A9, Canada.
Institut National de La Recherche Scientifique (INRS), Centre Eau Terre Environnement (ETE), 490 De La Couronne, Québec City, Québec, G1K 9A9, Canada.
J Environ Manage. 2024 Nov;370:122687. doi: 10.1016/j.jenvman.2024.122687. Epub 2024 Oct 8.
Lake St. Charles, located north of Quebec City, Canada, is a shallow fluvial lake with two distinct basins bridging rural and urban landscapes. Mainly used as a source of drinking water for 300,000 residents, the lake has faced a steady degradation in water quality due to urbanization and the discharge of domestic wastewater. This study introduces a 3D hydrodynamics and water quality model using the Environmental Fluid Dynamics Code to enhance our understanding of algal bloom dynamics in Lake St. Charles. More specifically, we ran simulations for eight years (i.e., a three-year period for calibration, 2015 to 2017; and a five-year period for validation, 2018 to 2022) to reproduce the complex circulation patterns and dynamics of water quality within the system. The simulation results for chlorophyll-a demonstrate seasonal fluctuations in phytoplankton biomass, closely aligning with in situ observations and achieving Relative Root Mean Square Error (RRMSE) values below 50%. (i) In spring, runoff from snowmelt brought phosphorus into the lake, triggering primary production. Diatom growth was initially predominant in the shallow southern basin, then spread to the deeper northern basin due to favorable environmental conditions, including flow- and wind-induced currents, warmer water temperatures and nutrient availability. (ii) In summer, warm water temperatures stimulated biological activity, leading to the growth of cyanobacteria at the expense of diatoms, as well as a drop in phosphorus. (iii) The cyanobacteria persisted into the fall but began to decline in mid-November. (iv) Winter conditions, including the presence of an ice cover, limited the input of phosphorus and minimized phytoplankton production, but diatoms were observed in low concentrations near Des Hurons River inflow. Overall, during the open-water period, the lake-maintained chlorophyll-a concentrations indicative of mesotrophic conditions, with occasional periods when the biomass increased above the eutrophic threshold. Temperature, nutrient levels, and the fluvial dynamics of the lake are the primary factors influencing phytoplankton formation and distribution in lake St. Charles.
加拿大魁北克市北的圣查尔斯湖是一个浅河流湖泊，拥有两个截然不同的流域，连接着农村和城市景观。该湖主要为 30 万居民提供饮用水，但由于城市化和生活污水排放，其水质一直在稳步下降。本研究使用环境流体动力学代码引入了一个三维水动力和水质模型，以增强我们对圣查尔斯湖藻类爆发动态的理解。更具体地说，我们进行了八年的模拟（即三年的校准期，2015 年至 2017 年；五年的验证期，2018 年至 2022 年），以再现系统内复杂的循环模式和水质动态。叶绿素-a 的模拟结果显示浮游植物生物量呈季节性波动，与现场观测结果密切吻合，相对均方根误差（RRMSE）值低于 50%。（i）在春季，融雪径流将磷带入湖中，引发初级生产。硅藻生长最初在浅南部流域占主导地位，然后由于有利的环境条件（包括水流和风引起的水流、温暖的水温以及养分的可用性）扩展到较深的北部流域。（ii）在夏季，温暖的水温刺激了生物活动，导致蓝藻生长，而硅藻减少，磷也减少。（iii）蓝藻一直持续到秋季，但在 11 月中旬开始减少。（iv）冬季条件，包括冰盖的存在，限制了磷的输入，最大限度地减少了浮游植物的产生，但在 Des Hurons 河流入流附近观察到硅藻浓度较低。总体而言，在敞水期，该湖保持了指示中营养状态的叶绿素-a 浓度，偶尔会出现生物量增加超过富营养阈值的情况。温度、营养水平和湖泊的河流动力学是影响圣查尔斯湖浮游植物形成和分布的主要因素。
