Effects of the reduction of submarine groundwater discharge (SGD) on thermal habitats for manatee in the Homosassa River, a spring-fed estuary in Florida, were studied using a laterally averaged hydrodynamic model. The estuary receives its hydrologic loading from numerous spring vents, mainly located at its headwaters and two upstream tributaries. The model was calibrated and verified against real-time data collected during November 2014 - August 2017 before it was used to simulate hydrodynamics, salinity transport, and thermal dynamics in the estuary from October 9, 2007 to March 12, 2018 with various SGD reductions. Effects of the SGD reduction on chronic (72-hour timescale) and acute (4-hour timescale) thermal habitats for manatee were analyzed at five critical time points (CTPs), including those of the lowest air temperature in 2010 and 2018, the lowest water temperature, the minimum thermal habitats, and the most sensitive extremely low habitats.

It is found that the chronic thermal habitats for manatee decrease linearly with the increase of the SGD reduction at these CTPs. When chronic thermal habitats are extremely low, they are most sensitive to the SGD reduction. Every 1% reduction of the SGD could cause roughly a 1.31 – 1.32% reduction of ≥ 20°C water volume and a 1.28% reduction of ≥ 20°C surface area. The chronic thermal habitats for manatee in the Homosassa River can be predicted using a simple heat flux parameter $\left(H_f\right)$, which explains 92% and 93% of the total variances of ≥ 20°C water volume and surface area, respectively using a logarithm relationship. The linearity of the relationships between the acute thermal habitats for manatee and the SGD reduction is weak. In fact, when acute thermal habitats in the estuary are extremely low, their relationships with the SGD reduction are very nonlinear, with the global minimum points varying significantly for various SGD reductions.

使用横向平均水动力模型研究了减少海底地下水排放 (SGD) 对 Homosassa 河（佛罗里达州的一个泉水河口）海牛热栖息地的影响。河口从主要位于其源头和两个上游支流的许多泉水口接收水文负荷。该模型根据 2014 年 11 月至 2017 年 8 月期间收集的实时数据进行了校准和验证，然后用于模拟 2007 年 10 月 9 日至 2018 年 3 月 12 日期间不同 SGD 减少的河口的流体动力学、盐度输送和热动力学。在五个关键时间点 (CTP) 分析了 SGD 减少对海牛慢性（72 小时时间尺度）和急性（4 小时时间尺度）热栖息地的影响，包括 2010 年和 2018 年最低气温的时间点，

发现海牛的慢性热栖息地随着这些 CTP 处 SGD 减少的增加而线性减少。当长期热栖息地极低时，它们对 SGD 的减少最为敏感。SGD 每减少 1%，就会导致 ≥ 20°C 的水量大约减少 1.31 – 1.32%，以及≥ 20°C 的表面积减少 1.28%。可以使用简单的热通量参数预测 Homosassa 河中海牛的长期热栖息地$\left(H_F\right)$，这使用对数关系分别解释了 ≥ 20°C 水体积和表面积总方差的 92% 和 93%。海牛的急性热栖息地与 SGD 减少之间的线性关系很弱。事实上，当河口的急性热栖息地极低时，它们与 SGD 减少的关系是非常非线性的，对于各种 SGD 减少，全局最小值点变化很大。