Longer duration of seasonal stratification contributes to widespread increases in lake hypoxia and anoxia
Longer duration of seasonal stratification contributes to widespread increases in lake hypoxia and anoxia
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DOI：
10.1111/gcb.16525
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发表时间：
2022-12-06
影响因子：
11.6
通讯作者：
Rose, Kevin C.
中科院分区：
文献类型：
--
作者：
Jane, Stephen F.;Mincer, Joshua L.;Rose, Kevin C.
溶解氧（DO）浓度是水生生态系统的一个重要属性，影响栖息地、饮用水质量、生物多样性、营养物地球化学和温室气体排放。虽然温带湖泊夏季溶解氧平均浓度正在下降，但导致深水溶解氧损失的季节性因素仍有很多未知之处。目前尚不清楚下降是否与季节性溶解氧耗竭率增加或季节性分层变化有关，这些变化限制了深层沃茨的再氧化。此外，尽管存在重要的生物和生态溶解氧阈值，一直没有大规模的评估，在数量的变化的栖息地跨越这些阈值，限制了能力，以了解所观察到的溶解氧损失的后果。我们使用了来自400多个广泛分布的湖泊的数据集，以确定DO损失的驱动因素，并量化湖水越过生物和生态重要阈值浓度（5至0.5 mg/L）的频率和体积。我们的研究结果表明，虽然季节性溶解氧消耗率随时间的推移没有一致的变化，但超过四分之三的湖泊表现出分层持续时间的增加，为季节性深水溶解氧消耗提供了更多的时间。因此，大多数湖泊都经历了夏季增加的水量低于所有检查的阈值在深水溶解氧浓度，增加的水柱低于阈值的比例范围在0.9%和1.7%之间每十年。在分层结束前的30天内，每十年增加>2.2%，超过70%的分析湖泊经历了贫氧水数量的增加。这些结果表明，正在进行的气候引起的增加，在分层的持续时间已经减少了许多物种的栖息地，可能增加内部营养负荷，否则改变湖泊化学。未来的气候变暖可能会加剧这些趋势。
The concentration of dissolved oxygen (DO) is an important attribute of aquatic ecosystems, influencing habitat, drinking water quality, biodiversity, nutrient biogeochemistry, and greenhouse gas emissions. While average summer DO concentrations are declining in lakes across the temperate zone, much remains unknown about seasonal factors contributing to deepwater DO losses. It is unclear whether declines are related to increasing rates of seasonal DO depletion or changes in seasonal stratification that limit re-oxygenation of deep waters. Furthermore, despite the presence of important biological and ecological DO thresholds, there has been no large-scale assessment of changes in the amount of habitat crossing these thresholds, limiting the ability to understand the consequences of observed DO losses. We used a dataset from >400 widely distributed lakes to identify the drivers of DO losses and quantify the frequency and volume of lake water crossing biologically and ecologically important threshold concentrations ranging from 5 to 0.5 mg/L. Our results show that while there were no consistent changes over time in seasonal DO depletion rates, over three-quarters of lakes exhibited an increase in the duration of stratification, providing more time for seasonal deepwater DO depletion to occur. As a result, most lakes have experienced summertime increases in the amount of water below all examined thresholds in deepwater DO concentration, with increases in the proportion of the water column below thresholds ranging between 0.9% and 1.7% per decade. In the 30-day period preceding the end of stratification, increases were greater at >2.2% per decade and >70% of analyzed lakes experienced increases in the amount of oxygen-depleted water. These results indicate ongoing climate-induced increases in the duration of stratification have already contributed to reduction of habitat for many species, likely increased internal nutrient loading, and otherwise altered lake chemistry. Future warming is likely to exacerbate these trends.