Whole‐lake methane emissions from two temperate shallow lakes with fluctuating water levels: Relevance of spatiotemporal patterns
Whole‐lake methane emissions from two temperate shallow lakes with fluctuating water levels: Relevance of spatiotemporal patterns
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DOI：
10.1002/lno.11764
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发表时间：
2021-05
影响因子：
4.5
通讯作者：
Marcel Schmiedeskamp;L. Praetzel;D. Bastviken;K. Knorr
中科院分区：
文献类型：
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作者：
Marcel Schmiedeskamp;L. Praetzel;D. Bastviken;K. Knorr
在全球范围内，浅水湖泊是向大气排放甲烷（CH4）的重要来源。以前对此类湖泊的研究很少关注湖内时空变化，这对于产生代表性的全湖通量以及更好地理解和限制大规模排放至关重要。为了解决这个问题，我们在近两年内每两周测定了中欧两个小型浅水湖（≤ 150 cm）的 CH4 通量和 CH4 浓度的变化情况。我们发现这两个湖都是甲烷的来源，主要是通过沸腾。在暂时干涸的较浅的 Heideweiher 湖，平均通量为 7.2 mmol m−2 d−1，从未干涸的 Windsborn 湖的平均通量为 3.5 mmol m−2 d−1。空间差异（湖泊之间和内部）与沉积物碳含量和质量密切相关，而沉积物碳含量和质量又与深度或距海岸的距离有关。最高通量出现在两个湖的中心部分。通量的时间变化主要与沉积物温度和干燥程度（自干燥以来的时间测量）相关。全湖的估计主要是低水期和温暖的夏季。总体而言，我们表明短期和小规模测量无法解释小湖泊 CH4 通量的高变异性，而可靠的大规模评估需要考虑这种时空变异性。
Globally, shallow lakes are an important source of methane (CH4) emissions to the atmosphere. Previous studies of such lakes have rarely focused on the within‐lake spatiotemporal variability, which is critical for generating representative whole‐lake fluxes, and better understanding and constrain large‐scale emissions. To address this issue, we determined the variability of CH4 fluxes and CH4 concentrations in two small shallow (≤ 150 cm) lakes in Central Europe biweekly over almost 2 years. We found that both lakes were a source of CH4, mainly by ebullition. At the shallower Lake Heideweiher, which temporarily dried out, the average flux was 7.2 mmol m−2 d−1, the average flux from Lake Windsborn that never dried out, was 3.5 mmol m−2 d−1. The spatial differences (between and within lakes) were most strongly related to sediment C‐content and quality, which in turn was linked to depth or distance to shore. The highest fluxes occurred in the central parts of both lakes. The temporal variability of the fluxes was primarily correlated with sediment temperature and degree of drying measured as the time since drying up. The whole‐lake estimates were dominated by low water periods and the warm summer months. Overall, we show that short‐term and small‐scale measurements cannot account for the high variability of CH4 fluxes from small lakes, and that reliable large‐scale assessments need to consider such spatiotemporal variability.