【摘要】 山地深水湖库是我国西南地区兼具防洪、发电、供水和观光等多重功能的重要水体，但近年来频发蓝藻水华，威胁水生态健康与人居环境。本研究以重庆石柱藤子沟水库为例，于2022—2023年开展水质、藻类、鱼类及底栖动物监测，系统诊断其生态健康状况并识别风险驱动机制。结果表明：水库水质总体为Ⅲ类，但总磷、溶解氧、酸碱度超标率分别达47.78%、 26.54%和24.69%；水体呈中营养—轻度富营养状态，夏季蓝藻密度峰值达1.79×10~7 cells/L，形成轻度水华，主要受高温、营养盐（以农业面源为主）及水体温度分层共同驱动。建议构建“监测预警—抑藻控源—生态修复”一体化防控体系，推广兼具净化与景观功能的生态工程，从而有效保障山地湖库水生态健康，持续提升人居环境质量。更多还原

【Abstract】 Mountainous deep-water reservoirs, formed by damming river channels and impounding water in valley depressions, represent a distinctive landscape type in southwest China. These reservoirs provide essential ecosystem services—including flood control, hydropower generation, water supply, and recreational opportunities—and are increasingly recognized as critical nodes for regional ecological security and human well-being. A representative case is the Tengzigou Reservoir in Chongqing’ s Shizhu County, designated as a National Wetland Park in 2019 due to its ecological and scenic value. Since 2014, this reservoir has experienced recurrent seasonal cyanobacterial blooms, raising concerns about aquatic ecological health and the suitability of the local living environment.To address these challenges, this study conducted comprehensive in situ monitoring from April 2022 to March 2023 across eight sampling sites within the reservoir and its two main tributaries(Shazi River and Yuelai River). The investigation integrated physical, chemical, and biological indicators—including water quality parameters(e. g., total phosphorus, dissolved oxygen, p H, total nitrogen), phytoplankton community structure, fish assemblages, and benthic macroinvertebrates—to holistically assess the reservoir’ s ecological status. Results indicated that the overall water quality of Tengzigou Reservoir was classified as Grade III according to China’ s Surface Water Environmental Quality Standards(GB 3838–2002). However, significant spatiotemporal heterogeneity was observed. Total phosphorus exhibited the highest exceedance rate at 47.78%, with concentrations ranging from 0.003 to 0.35 mg/L(mean: 0.05 mg/L). Dissolved oxygen fell below the Class III threshold in 26.54% of samples, with some deep-layer measurements dropping below 1 mg/L, indicating localized hypoxia. p H exceeded the upper limit of 9 in 24.69% of samples, with a mean value of 8.17. Total nitrogen exceeded the Class III standard in 16.96% of samples(range: 0.11 – 2.05 mg/L; mean: 0.65 mg/L), while ammonia nitrogen and chemical oxygen demand rarely surpassed thresholds. The reservoir is in a mesotrophic to lightly eutrophic state. Chlorophyll-a concentrations ranged from 1.4 to 17.5 μg/L(mean: 6.6 μg/L), with 9.36% of values exceeding 10 μg/L—indicative of elevated algal biomass. A total of 13 algal species were identified, primarily comprising green algae, cyanobacteria, diatoms, cryptophytes, and dinoflagellates. Cyanobacteria dominated during summer months(June to October), peaking in July when they accounted for 70.38% of the phytoplankton community. Bluegreen algal density reached a maximum of 1.79×107 cells/L in July 2022 at the Yuelai River inflow zone(S5 to S7), constituting a mild surface bloom. Densities were significantly lower in spring and winter, with cyanobacteria undetectable from December to March.Biological surveys recorded 24 fish species, including 20 Cypriniformes, 1 Perciformes, and 3 Siluriformes. Dominant species included crucian carp, common carp, silver carp, and topmouth gudgeon. Six species were endemic to China, and one invasive species(mirror carp) was detected. Most fish(21 of 24) were adapted to lentic or slow-flowing habitats, reflecting the reservoir’ s altered hydrology. Trophic composition included 11 omnivorous, 10 carnivorous, and 3 herbivorous species, suggesting a moderately complex food web without strong dominance by filter-feeders. A total of 23 benthic taxa were identified, predominantly aquatic insects(22 taxa), especially Diptera(Chironomidae) and Ephemeroptera, along with one annelid species. Chironomid larvae dominated in the reservoir core(S4) from August to October, while site-specific shifts occurred in tributaries—such as Trichoptera in Yuelai River in August, and different Ephemeroptera genera in September and October. The prevalence of pollution-tolerant Chironomidae indicates potential eutrophication stress.Vertical profiling revealed strong thermal stratification in the deep reservoir basin(S3) during summer. A distinct thermocline formed between 2-5 m depth in July, with a temperature gradient exceeding 10 ℃ between epilimnion and hypolimnion. In contrast, inflow rivers(e. g., S1) remained fully mixed throughout the monitoring period. Nutrient analysis showed that total phosphorus concentrations averaged 0.04 mg/L in July—exceeding the 0.02 mg/L bloom warning threshold—but declined sharply to 0.006 mg/L by September during prolonged dry conditions with minimal rainfall. This rapid decrease, coinciding with the cessation of surface runoff, underscores the dominant contribution of agricultural nonpoint sources to phosphorus loading, as further confirmed by source apportionment indicating that 85% of total phosphorus originated from agricultural activities. These results indicate that the Tengzigou Reservoir watershed maintains a generally favorable aquatic ecological condition, yet faces latent risks. While biological indicators suggest the absence of severe eutrophication, recurrent seasonal cyanobacterial blooms remain a concern. These blooms are closely linked to high water temperatures, elevated phosphorus levels—primarily from agricultural non-point sources—and summer thermal stratification. To address these challenges, it recommends establishing a bloom monitoring and early-warning system tailored to mountainous deep-water reservoirs. Ecological reservoir operations should be optimized to weaken thermal stratification, while algal suppression measures can be deployed in high-risk zones. Crucially, watershedscale control of agricultural runoff—through buffer strips, improved fertilizer management, and best practices—is essential to reduce phosphorus loading. Integrating ecological functions with aesthetic landscape design along shorelines can further enhance both water quality and livability. Sustained implementation of this integrated approach will support long-term ecological resilience and regional sustainability.更多还原