We investigated trends in temperature, stratification, and hypolimnetic oxygen concentration of German lakes under climate change using observational data and hydrodynamic modelling. Observations from 46 lakes revealed that annually averaged surface temperatures increased by + 0.5 °C between 1990 and 2020 while bottom temperatures remained almost constant. Modelling of 12 lakes predicted further increases in surface temperatures by 0.3 °C/decade until the year 2099 in the most pessimistic emission scenario RCP 8.5 (RCP 4.5: + 0.18 °C/decade; RCP 2.6: + 0.04 °C/decade). Again, bottom temperatures increased much less while summer stratification extended by up to 38 days. Using a simplified oxygen model, we showed that hypolimnetic oxygen concentrations decreased by 0.7–1.9 mg L⁻¹ in response to the extended stratification period. However, model runs assuming lower productivity (e. g. through nutrient reduction) resulted in increased oxygen concentrations even in the most pessimistic emission scenario. Our results suggest that the negative effects of climate change on the oxygen budget of lakes can be efficiently mitigated by nutrient control.

我们利用观测数据和水动力模型研究了气候变化下德国湖泊的温度、分层和低湖氧浓度的趋势。对 46 个湖泊的观测显示，1990 年至 2020 年间，年平均表面温度增加了 + 0.5 °C，而底部温度几乎保持不变。对 12 个湖泊的建模预测，在最悲观的排放情景 RCP 8.5（RCP 4.5：+ 0.18 °C/十年；RCP 2.6：+ 0.04 °C/十年）中，直到 2099 年，地表温度将进一步上升 0.3 °C/十年。同样，底部温度的上升幅度要小得多，而夏季分层则延长了 38 天。使用简化的氧气模型，我们发现，随着分层时间的延长，低浅层氧气浓度降低了 0.7–1.9 mg L ⁻¹ 。然而，模型运行假设生产率较低（例如通过养分减少），即使在最悲观的排放情况下也会导致氧气浓度增加。我们的结果表明，气候变化对湖泊氧气收支的负面影响可以通过营养物控制有效减轻。