Eddy correlation measurements of oxygen fluxes in permeable sediments exposed to varying current flow and light
Eddy correlation measurements of oxygen fluxes in permeable sediments exposed to varying current flow and light
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DOI：
10.4319/lo.2013.58.4.1329
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发表时间：
2013-07-01
影响因子：
4.5
通讯作者：
Marino, Roxanne
中科院分区：
文献类型：
--
作者：
Berg, Peter;Long, Matthew H.;Marino, Roxanne
基于海洋和淡水地点的无创涡流相关测量，本研究记录了水流和光对可渗透沉积物中沉积物-水氧通量的控制。海洋沉积物暴露于潮汐驱动的水流和光下，氧气通量从夜间到白天在-29至78 mmol m(-2) d(-1)之间变化。拟合模型假设氧气呼吸随电流流量线性增加，并且光控生产的光合作用-辐照度曲线很好地再现了测量的通量（R-2 = 0.992），并显示当电流速度从大约 0 增加到 20 cm s(-1) 时，摄氧量增加了 4 倍。将该模型应用于为期一周的海流速度和光测量记录表明，由于光和海流的变化，生态系统净代谢在不同天数之间变化很大，在-27至31 mmol m(-2) d(-1)之间。这种变化可能是许多浅水系统的典型现象，并强调需要长期通量积分来准确确定系统代谢。在淡水河流域，沉积物-水氧通量范围为-360至137 mmol m(-2) d(-1)。夜间与同时进行的海底箱孵化的直接比较显示，涡流比箱中获得的涡流大 4.1 倍。本次比较中的水流速度为31 cm s(-1)，较大的差异可能是由于在这种高水流速度下自然孔隙水冲刷室的模拟效果不佳造成的。这些结果强调需要对可渗透沉积物进行更多非侵入性氧通量测量，以准确评估其在当地和全球碳预算中的作用。
Based on noninvasive eddy correlation measurements at a marine and a freshwater site, this study documents the control that current flow and light have on sediment-water oxygen fluxes in permeable sediments. The marine sediment was exposed to tidal-driven current and light, and the oxygen flux varied from night to day between -29 and 78 mmol m(-2) d(-1). A fitting model, assuming a linear increase in oxygen respiration with current flow, and a photosynthesis-irradiance curve for light-controlled production reproduced measured fluxes well (R-2 = 0.992) and revealed a 4-fold increase in oxygen uptake when current velocity increased from similar to 0 to 20 cm s(-1). Application of the model to a week-long measured record of current velocity and light showed that net ecosystem metabolism varied substantially among days, between -27 and 31 mmol m(-2) d(-1), due to variations in light and current flow. This variation is likely typical of many shallow-water systems and highlights the need for long-term flux integrations to determine system metabolism accurately. At the freshwater river site, the sediment-water oxygen flux ranged from -360 to 137 mmol m(-2) d(-1). A direct comparison during nighttime with concurrent benthic chamber incubations revealed a 4.1 times larger eddy flux than that obtained with chambers. The current velocity during this comparison was 31 cm s(-1), and the large discrepancy was likely caused by poor imitation by the chambers of the natural pore-water flushing at this high current velocity. These results emphasize the need for more noninvasive oxygen flux measurements in permeable sediments to accurately assess their role in local and global carbon budgets.