Benthic Flow and Mixing in a Shallow Shoal Grass (Halodule wrightii) Fringe
Benthic Flow and Mixing in a Shallow Shoal Grass (Halodule wrightii) Fringe
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DOI：
10.3390/geosciences11030115
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
D. Cannon;K. Kibler;V. Kitsikoudis
中科院分区：
文献类型：
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作者：
D. Cannon;K. Kibler;V. Kitsikoudis
平均流量和湍流测量收集在一个浅的Haloelasticwrightii浅滩草边缘突出了显着的异质性，在相对较小的空间尺度上的水动力效应。在植被冠层（底部以上约4厘米）内进行了相对稀疏（40%覆盖率）和密集（70%覆盖率）植被的实验，并在裸露沉积物上方的床附近收集了参考测量值。在所有采样点均观察到显著的底栖速度剪切，在两个植被覆盖点，冠层剪切层几乎穿透到海床。在所有样本位置（P/Δ 1），湍流剪切产生（P）与湍流动能耗散（Δ 1）平衡，表明茎产生的湍流在总体湍流预算中起次要作用。而植被稀疏的采样点与增强的通道到海岸的速度衰减有关（71.4 ± 1.0%）相对于裸露沉积物上的水流（51.7 ± 2.2%），在近岸密集林冠（VNS）观测到了意想不到的强越岸流，其量级几乎是在主航道测量的两倍（VCH; VNS/VCH <$= 1.81 ± 0.08）。这些结果突出了内和跨冠层运输的流量转向和加速的重要性，特别是在单个植被斑块的规模，营养盐和沉积物通量的重要影响。重要的是，这项工作是对浅水沿海河口浅滩草缘的首批水动力研究之一，也是唯一关于H内湍流混合的报告之一。赖特氏树冠。
Mean flow and turbulence measurements collected in a shallow Halodule wrightii shoal grass fringe highlighted significant heterogeneity in hydrodynamic effects over relatively small spatial scales. Experiments were conducted within the vegetation canopy (~4 cm above bottom) for relatively sparse (40% cover) and dense (70% cover) vegetation, with reference measurements collected near the bed above bare sediment. Significant benthic velocity shear was observed at all sample locations, with canopy shear layers that penetrated nearly to the bed at both vegetated sites. Turbulent shear production (P) was balanced by turbulent kinetic energy dissipation (ϵ) at all sample locations (P/ϵ≈1), suggesting that stem-generated turbulence played a minor role in the overall turbulence budget. While the more sparsely vegetated sample site was associated with enhanced channel-to-shore velocity attenuation (71.4 ± 1.0%) relative to flows above bare sediment (51.7 ± 2.2%), unexpectedly strong cross-shore currents were observed nearshore in the dense canopy (VNS), with magnitudes that were nearly twice as large as those measured in the main channel (VCH; VNS/VCH¯ = 1.81 ± 0.08). These results highlight the importance of flow steering and acceleration for within- and across-canopy transport, especially at the scale of individual vegetation patches, with important implications for nutrient and sediment fluxes. Importantly, this work represents one of the first hydrodynamic studies of shoal grass fringes in shallow coastal estuaries, as well as one of the only reports of turbulent mixing within H. wrightii canopies.