Air–water exchange rates of gasses, such as O₂, CO₂, and CH₄, are widely used in ecosystem studies of lakes and reservoirs, but their magnitudes are often difficult to assess. In this proof‐of‐concept study, we measured gas exchange by underwater eddy covariance in such lentic systems from a moving platform. We used an Acoustic Doppler Velocimeter and a fast‐responding O₂‐temperature sensor mounted in the bow of a boat to measure water velocity, O₂ concentration, and temperature below the air–water interface (~ 10 cm) while the boat was propelled at constant speed (~ 25 cm s⁻¹) by an electric trolling motor. Fluxes of O₂ and heat across the air–water interface and standard gas exchange coefficients, k₆₀₀, were calculated for every 3 min of traveled distance (~ 45 m). All deployments were done under calm low‐wind conditions where empirical relationships for k₆₀₀ are most uncertain. Deployment averages of k₆₀₀ ranged from 0.070 to 0.39 m d⁻¹ and were strongly correlated with both the heat flux and the water temperature. In one deployment, a > 20% variation in mean water column O₂ concentration was measured along a 1 km long transect of a reservoir. Given the typical size of O₂ concentration differences over the air–water interface that drive gas exchange, such lateral variations can, even at a near‐constant exchange coefficient, result in highly biased whole‐ecosystem fluxes if based on stationary single‐point O₂ measurements. “Mobile” aquatic eddy covariance measurements enable quantification of gas exchange in lakes and reservoirs under true in situ conditions and with high temporal and spatial resolution.

中文翻译：

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通过水下涡动协方差从移动平台测量的湖泊和水库中的空气-水气体交换

O ₂，CO ₂和CH ₄等气体的气水交换率已广泛用于湖泊和水库的生态系统研究，但其幅度通常难以评估。在此概念验证研究中，我们通过移动平台在此类透镜系统中通过水下涡动协方差测量了气体交换。我们使用声学多普勒测速仪和快速响应的O ₂温度传感器，该传感器安装在船头，测量船推进时水速，O ₂浓度和空气-水界面以下的温度（〜10 cm）电动拖曳电机以恒定速度（〜25 cm s ^-1）以恒定速度行驶。O _2的通量每行驶3分钟（〜45 m）计算一次空气-水界面的热量，标准气体交换系数k ₆₀₀。所有部署都是在平静的低风条件下完成的，其中k _600的经验关系最不确定。k _600的部署平均值在0.070到0.39 md ^-1之间，并且与热通量和水温密切相关。在一种部署中，沿着水库1公里长的横断面测量了平均水柱O ₂浓度的变化> 20％。鉴于O ₂的典型大小如果基于固定的单点O ₂测量值，则在驱动气体交换的空气-水界面上的浓度差异，即使在接近恒定的交换系数下，这种横向变化也可能导致整个生态系统通量高度偏差。“移动式”水生涡流协方差测量能够在真实的原位条件下以高时空分辨率量化湖泊和储层中的气体交换。