Abstract Horne AJ, Beutel M. 2019. Hypolimnetic oxygenation 3: an engineered switch from eutrophic to a meso-/oligotrophic state in a California reservoir. Lake Reserv Manage. 35:338–353. A long-term improvement in water quality due to a hypolimnetic oxygenation system (HOS) used without other management actions was shown for Camanche Reservoir in California (volume = 514 million m3). Prior to oxygenation, the reservoir was eutrophic with low water clarity, high chlorophyll a (Chl-a), and blooms of cyanobacteria primarily caused by internal nutrient loading from anoxic sediments. All 4 trophic state indicators showed major improvement, most pointing to a new oligotrophic state. Days after HOS startup in July 1993, hypolimnion soluble phosphate and ammonium concentrations declined and, unexpectedly, nitrate remained low. This report covers pre-HOS (1988 to mid-1993) and 12 yr of post-HOS measurements (mid-1993 to mid-2005). For surface waters during the growth season (Apr–Oct) after HOS, average Chl-a decreased 79% (14.6–3.1 μg/L) and peak Chl-a decreased sixfold (from 49 to 8 μg/L). Average Secchi depth increased 10-fold (0.47 to 4.9 m) and peak Secchi depth doubled (4.2–8 m). Cyanobacteria (Aphanizomenon and Dolichospermum, formerly Anabaena) decreased >95% while the previously absent Merismopedia, an indicator of clean water, appeared. The large colonial diatom Fragilaria also decreased by >90%. Zooplankton (rotifers and crustaceans) appeared unchanged. After HOS, late winter surface nutrients prior to the next spring bloom were much reduced (total phosphorus, TP, by 58%, total inorganic nitrogen, TIN, by 88%). The TIN:TP ratio dropped from 6 to 1.6. In 2004, the last full year of measurements, further declines were found for nitrate nitrogen (42–3 μg/L) and Chl-a (3.1–2.8 μg/L) while TP was unchanged (14 μg/L).

中文翻译：

---

Hypolimnetic 氧合 3：在加利福尼亚水库中从富营养状态到中/贫营养状态的工程转换

摘要 Horne AJ, Beutel M. 2019. Hypolimnetic 氧合 3：在加利福尼亚水库中从富营养状态到中/贫营养状态的工程转换。湖泊保护区管理。35:338-353。加利福尼亚州的卡曼奇水库（容积 = 5.14 亿立方米）显示，由于在没有其他管理措施的情况下使用了低温氧合系统 (HOS)，水质得到了长期改善。在充氧之前，水库是富营养化的，水透明度低，叶绿素 a (Chl-a) 高，蓝藻大量繁殖，主要是由缺氧沉积物的内部养分负荷引起的。所有 4 项营养状态指标都显示出重大改善，大多数都指向新的贫营养状态。1993 年 7 月 HOS 启动几天后，水下可溶磷酸盐和铵浓度下降，出乎意料的是，硝酸盐仍然很低。本报告涵盖居屋前（1988 年至 1993 年中）和居屋后 12 年（1993 年中至 2005 年中）的测量。对于居屋后的生长季节（4 月至 10 月）地表水，平均 Chl-a 下降了 79%（14.6-3.1 μg/L），峰值 Chl-a 下降了六倍（从 49 到 8 μg/L）。平均 Secchi 深度增加了 10 倍（0.47 到 4.9 m），峰值 Secchi 深度增加了一倍（4.2-8 m）。蓝藻（Aphanizomenon 和 Dolichospermum，以前的鱼腥藻）减少了 95% 以上，而以前没有的分生藻（一种清洁水的指标）出现了。大型群落硅藻 Fragilaria 也减少了 >90%。浮游动物（轮虫和甲壳类动物）看起来没有变化。在 HOS 之后，下一次春季开花前的晚冬地表养分大大减少（总磷、TP 减少 58%，总无机氮 TIN 减少 88%）。TIN:TP 比率从 6 下降到 1.6。