Browning-related oxygen depletion in an oligotrophic lake
Browning-related oxygen depletion in an oligotrophic lake
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DOI：
10.1080/20442041.2018.1452355
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发表时间：
2018-01-01
期刊：
影响因子：
3.1
通讯作者：
Fisher, Thomas J.
中科院分区：
文献类型：
--
作者：
Knoll, Lesley B.;Williamson, Craig E.;Fisher, Thomas J.
近几十年来，北美东北部和欧洲许多湖泊的陆地溶解有机质（DOM）增加，并导致长期褐化。我们使用了一个长期数据集（1988-2014），研究了美国宾夕法尼亚州两个不同溶解有机碳浓度的温带小湖泊中与褐化相关的水透明度降低对溶解氧动态的影响。低营养（“更清澈”）湖泊的生产力低，历史上是含氧的深水。中营养-轻度营养不良（“棕色”）湖的生产力也相对较低，但历史上缺氧的深水。我们研究了褐变是否与夏季溶解氧动力学的变化相一致，重点是深水氧气消耗。在较清澈的湖泊中，我们发现最低氧浓度在27年期间下降了4.4 mg L-1，这些变化与水透明度下降和水柱稳定性增加密切相关。我们还发现最大溶解氧深度变浅了4.5米，并且近年来建立了缺氧条件。在棕色湖泊中，我们使用的指标没有检测到溶解氧的任何显著变化，这支持了预测，即清澈湖泊的垂直温度和氧气模式可能比深色湖泊对DOM的增加更敏感。缺氧传统上被认为是人为的营养负荷和最近的气候变暖的结果。我们表明褐变是另一种类型的环境变化，可能类似地导致贫营养湖泊缺氧。
In recent decades, terrestrial dissolved organic matter (DOM) has increased in many northeastern North American and European lakes and is contributing to long-term browning. We used a long-term dataset (1988-2014) to study the consequences of browning-related decreased water transparency on dissolved oxygen dynamics in 2 small temperate lakes in Pennsylvania, USA, that differ in their dissolved organic carbon concentrations. The oligotrophic ("clearer") lake has low productivity and historically oxygenated deep waters. The mesotrophic-slightly dystrophic ("browner") lake also has relatively low productivity but historically anoxic deep waters. We examined whether browning coincided with changes in summer dissolved oxygen dynamics, with a focus on deep-water oxygen depletion. In the clearer lake, we found that minimum oxygen concentrations decreased by similar to 4.4 mg L-1 over the 27-year period, and these changes were strongly associated with both decreased water transparency and increased water column stability. We also found a shallowing of the maximum dissolved oxygen depth by similar to 4.5 m and anoxic conditions established in more recent years. In the browner lake, the metrics we used did not detect any significant changes in dissolved oxygen, supporting the prediction that vertical temperature and oxygen patterns in clearer lakes may be more sensitive to increasing DOM than darker lakes. Anoxia is traditionally considered to be a consequence of anthropogenic nutrient loading and, more recently, a warming climate. We show that browning is another type of environmental change that may similarly result in anoxia in oligotrophic lakes.