Benthic oxygen consumption rates during hypoxic conditions on the Oregon continental shelf: Evaluation of the eddy correlation method
Benthic oxygen consumption rates during hypoxic conditions on the Oregon continental shelf: Evaluation of the eddy correlation method
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DOI：
10.1029/2011jc007564
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发表时间：
2012-02
影响因子：
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通讯作者：
C. Reimers;H. Özkan‐Haller;P. Berg;A. Devol;Kristina McCann-Grosvenor;Rhea D. Sanders
中科院分区：
文献类型：
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作者：
C. Reimers;H. Özkan‐Haller;P. Berg;A. Devol;Kristina McCann-Grosvenor;Rhea D. Sanders
[1]在2009年春末和夏季的缺氧条件下，研究了俄勒冈大陆架上44.7°N和43.9 N之间~ 80 m水深的三个站点，以确定底栖动物的耗氧量。氧通量是由每次部署11-15小时的自主着陆器进行的涡流相关（EC）测量得出的。平均耗氧量在3.2 ~ 9.8 mmol m−2 d−1之间，在最南端的站点最高。研究了分离涡流分量和旋转坐标的方法对涡流通量的影响。研究发现，与表面波和内波相关的频率上的振荡有显著的贡献，但水平分量的偏置可以通过基于波的旋转方法最小化。其他测量包括底栖边界层特性、沉积物渗透性和沉积物有机C、叶绿素-a、过量210Pb和%细粒的剖面。比较通量估计是根据两个站点的底栖生物室测量和微电极剖面确定的。室内氧气消耗速率超过EC通量的倍数为1.2 ~ 1.8，这可能反映了封闭效应、测量的时空尺度不同和/或底栖生物呼吸速率不均匀。然而，两种方法的通量值对于陆架深度来说都很低。因此，为了使底栖动物的氧气消耗促成俄勒冈大陆架缺氧，必须缓慢地更新底水，并通过沿大陆架或跨大陆架的平流和湍流混合来最低限度地通风。环流研究表明，在持续的夏季上升流-松弛周期中，增加的近底部分层有利于这些条件。
[1] Three stations, at ∼80 m water depth on the Oregon shelf between 44.7°N and 43.9 N, were studied under hypoxic conditions in late spring and summer of 2009 to determine benthic oxygen consumption rates. Oxygen fluxes were derived from eddy correlation (EC) measurements made from an autonomous lander deployed for 11–15 h at a time. Average oxygen consumption rates ranged from 3.2 to 9.8 mmol m−2 d−1 and were highest at the southernmost station. Methods for separating eddy components and rotating coordinates were examined for effects on EC fluxes. It was found that oscillations at frequencies associated with surface and internal waves made significant contributions, but horizontal component biasing could be minimized by wave-based rotation methods. Additional measurements included benthic boundary layer properties, and sediment permeability and profiles of sediment organic C, chlorophyll-a, excess 210Pb and % fines. Comparative flux estimates were determined from benthic chamber measurements and microelectrode profiles at two of the stations. The chamber O2 consumption rates exceeded the EC fluxes by factors of 1.2–1.8, which may reflect enclosure effects, the different spatial and temporal scales of the measurements, and/or inhomogeneous benthic respiration rates. The magnitudes of the fluxes by either method, however, are low for shelf depths. Thus, for benthic O2 consumption to contribute to Oregon shelf hypoxia, bottom waters must be slowly renewed and minimally ventilated by along- or across-shelf advection and turbulent mixing. Circulation studies indicate these conditions are favored by increased near-bottom stratification during persistent summer upwelling- relaxation cycles.