Shao Qianwen, Yang Qingchuan, Xu Yuankai, Zhang Ling, Ding Ming, Li Fan, He Congying
Ningbo Institute of Oceanography, Ningbo, 315832, China.
School of Marine Science, Ministry of Education, Ningbo University, Ningbo, 315832, China.
Microb Ecol. 2025 Aug 28;88(1):91. doi: 10.1007/s00248-025-02588-z.
Artificial water diversion is widely used to address water security; yet, its impacts on phytoplankton communities and coastal carbon balance remain poorly understood. Using a seasonal diversion project in a semi-enclosed bay as a case study, we analyzed phytoplankton composition via morphological methods and assessed carbon balance through simultaneous measurements of primary production (P), ecosystem respiration rate (R), and production-to-respiration (PP/R) ratio. Our results showed that artificial water diversion activities during the wet month enhanced hydrological connectivity and phytoplankton homogeneity, triggering a mixed diatom-dinoflagellate bloom. Phytoplankton abundance during the wet month increased by sevenfold (surface layer) and 26.5-fold (bottom layer) compared to dry month values. This simultaneously resulted in the PP value of the wet month being more than twice that of the dry month. Although R rose with increasing phytoplankton abundance, no significant correlation was observed between them. Instead, dry-month R was primarily driven by pH and dissolved organic carbon, whereas wet-month R showed minimal environmental linkages. PP/R ratios of surface and bottom layers were always less than 1, implying Meishan bay was a net heterotrophic ecosystem, despite significant changes in phytoplankton community structure induced by artificial water diversion and associated algal bloom. Furthermore, our results strongly suggest that changes in PP, but not in R, control the PP/R ratio of Meishan bay. This study offers valuable guidance for the ecological management of artificial water diversions and can serve as a reference for similar water diversion projects in other semi-enclosed bays.
人工引水被广泛用于解决水安全问题；然而，其对浮游植物群落和沿海碳平衡的影响仍知之甚少。以一个半封闭海湾的季节性引水工程为案例研究，我们通过形态学方法分析了浮游植物组成，并通过同时测量初级生产力（P）、生态系统呼吸速率（R）和生产与呼吸比（PP/R）来评估碳平衡。我们的结果表明，雨季的人工引水活动增强了水文连通性和浮游植物的同质性，引发了硅藻和甲藻混合水华。与旱季相比，雨季的浮游植物丰度在表层增加了7倍，在底层增加了26.5倍。这同时导致雨季的PP值是旱季的两倍多。虽然R随着浮游植物丰度的增加而上升，但两者之间未观察到显著相关性。相反，旱季的R主要受pH值和溶解有机碳的驱动，而雨季的R与环境的联系最小。表层和底层的PP/R比值始终小于1，这意味着梅山湾是一个净异养生态系统，尽管人工引水和相关藻华导致浮游植物群落结构发生了显著变化。此外，我们的结果强烈表明，PP的变化而非R的变化控制着梅山湾的PP/R比值。本研究为人工引水的生态管理提供了有价值的指导，并可为其他半封闭海湾的类似引水工程提供参考。
