In 2000, a total maximum daily load (TMDL) total phosphorus (TP) goal of 40 µg/L was established for Lake Okeechobee, Florida. The goal was selected to reduce the “imbalance to flora and fauna” caused by excessive phosphorus loading in the lake. We recalculate the TMDL TP goal using a water quality data series of TP and chlorophyll-a concentrations from 1986 to 2018 for the original 30 in-lake stations plus an additional 29 stations. Using the cross-tabulation approach used to generate the original TMDL TP goal, we determined a new goal of 42 µg/L, nominally different from the original. We also reevaluate the goal’s ability to maintain an implicit goal of 11.5% bloom frequency. We conclude substantial changes in the frequency and scope of the water quality sampling scheme prevent a determination on the effectiveness of the TMDL TP goal. The implementation, however, appears to have failed as the median TP concentration has increased by 93 µg/L to 133 µg/L and bloom frequency, after correcting for the declining sampling frequency, has increased from 1986 to 2018. An increased sampling frequency of TP and chlorophyll-a sampling is needed, or else tracking responses of chlorophyll-a to future TP reductions will be virtually impossible.

中文翻译：

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重新审视奥基乔比湖总最大日负荷总磷目标

2000 年，佛罗里达州奥基乔比湖的总最大日负荷 (TMDL) 总磷 (TP) 目标为 40 µg/L。选择目标是为了减少因湖中磷含量过高而导致的“动植物失衡”。我们使用 1986 年至 2018 年的 TP 和叶绿素-a 浓度的水质数据系列重新计算了 TMDL TP 目标，这些数据适用于最初的 30 个湖内站和另外 29 个站。使用用于生成原始 TMDL TP 目标的交叉表方法，我们确定了 42 µg/L 的新目标，名义上与原始目标不同。我们还重新评估了目标保持 11.5% 绽放频率的隐式目标的能力。我们得出结论，水质采样计划的频率和范围发生了实质性变化，这阻碍了对 TMDL TP 目标有效性的确定。