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Crab burrow aspect ratio influences particle capture rates on intertidal sandflats
Geo-Marine Letters ( IF 1.4 ) Pub Date : 2019-12-11 , DOI: 10.1007/s00367-019-00630-x
Marine Le Minor , Julia C. Mullarney , Conrad A. Pilditch , Katrin Huhn

Crabs are ecosystem engineers that dig burrows, which can trap sediment. We used a field experiment to explore how burrow aspect ratio (depth/diameter) affects the trapping efficiency of sediments and organic material. Arrays of burrows mimics were constructed using tubes of similar depths but two different opening diameters: fat tubes (aspect ratio of 3.8) and thin tubes (7.1). Different arrays were tested to examine whether the combination of burrows with two different aspect ratios affects the material capture, while retaining the same total area of openings per array. The results showed that, in general, the fat tubes trapped more organic material, especially large pieces, and more sediment than thin tubes. Furthermore, the silt-clay content of the sediment trapped in the tubes was up to 50% greater than the surrounding surficial sediment. Hence, we conducted 2D numerical simulations of flow around, and into, a single burrow to elucidate the mechanisms behind particle capture. Results showed that the flushing rate and the turbulent kinetic energy were greater in the fat tubes. However, turbulence persisted for a longer distance downstream of the thin tubes than the fat tubes. The enhanced turbulence may increase the flux of sediment into the tubes where particles can settle and, consequently, promote the sediment capture and sedimentation rate. Our results demonstrate that the aspect ratio of burrows significantly affects capture processes of organic material and sediment particles. Moreover, this capture mechanism depends on the flow regime, as faster flows are associated with larger amounts of material in the water column.

中文翻译:

蟹洞纵横比影响潮间带沙滩上的颗粒捕获率

螃蟹是生态系统工程师,可以挖洞穴,可以捕获沉积物。我们使用现场实验来探索洞穴纵横比(深度/直径)如何影响沉积物和有机物质的捕获效率。洞穴模拟物阵列是使用深度相似但开口直径不同的两种管子构建的:脂肪管(纵横比为 3.8)和细管(7.1)。测试了不同的阵列以检查具有两种不同纵横比的洞穴的组合是否会影响材料捕获,同时保持每个阵列的开口总面积相同。结果表明,总的来说,脂肪管比细管捕获更多的有机物质,尤其是大块,和更多的沉积物。此外,截留在管中的沉积物的粉砂粘土含量比周围的表层沉积物高 50%。因此,我们对单个洞穴周围和内部的流动进行了二维数值模拟,以阐明粒子捕获背后的机制。结果表明,脂肪管中的冲洗速度和湍流动能更大。然而,湍流在细管下游持续的距离比脂肪管更长。增强的湍流可能会增加沉积物进入管道的通量,颗粒可以在管道中沉降,从而促进沉积物捕获和沉降速率。我们的结果表明,洞穴的纵横比显着影响有机物质和沉积物颗粒的捕获过程。此外,这种捕获机制取决于流动状态,因为较快的流动与水柱中的大量物质有关。并进入一个洞穴,以阐明粒子捕获背后的机制。结果表明,脂肪管中的冲洗速度和湍流动能更大。然而,在细管下游的湍流比脂肪管持续更长的距离。增强的湍流可能会增加沉积物进入管道的通量,颗粒可以在管道中沉降,从而促进沉积物捕获和沉降速率。我们的结果表明,洞穴的纵横比显着影响有机物质和沉积物颗粒的捕获过程。此外,这种捕获机制取决于流动状态,因为较快的流动与水柱中的大量物质有关。并进入一个洞穴,以阐明粒子捕获背后的机制。结果表明,脂肪管中的冲洗速度和湍流动能更大。然而,湍流在细管下游持续的距离比脂肪管更长。增强的湍流可能会增加沉积物进入管道的通量,颗粒可以在管道中沉降,从而促进沉积物捕获和沉降速率。我们的结果表明,洞穴的纵横比显着影响有机物质和沉积物颗粒的捕获过程。此外,这种捕获机制取决于流动状态,因为较快的流动与水柱中的大量物质有关。结果表明,脂肪管中的冲洗速度和湍流动能更大。然而,湍流在细管下游持续的距离比脂肪管更长。增强的湍流可能会增加沉积物进入管道的通量,颗粒可以在管道中沉降,从而促进沉积物捕获和沉降速率。我们的结果表明,洞穴的纵横比显着影响有机物质和沉积物颗粒的捕获过程。此外,这种捕获机制取决于流动状态,因为较快的流动与水柱中的大量物质有关。结果表明,脂肪管中的冲洗速度和湍流动能更大。然而,湍流在细管下游持续的距离比脂肪管更长。增强的湍流可能会增加沉积物进入管道的通量,颗粒可以在管道中沉降,从而促进沉积物捕获和沉降速率。我们的结果表明,洞穴的纵横比显着影响有机物质和沉积物颗粒的捕获过程。此外,这种捕获机制取决于流动状态,因为较快的流动与水柱中的大量物质有关。增强的湍流可能会增加沉积物进入管道的通量,颗粒可以在管道中沉降,从而促进沉积物捕获和沉降速率。我们的结果表明,洞穴的纵横比显着影响有机物质和沉积物颗粒的捕获过程。此外,这种捕获机制取决于流动状态,因为较快的流动与水柱中的大量物质有关。增强的湍流可能会增加沉积物进入管道的通量,颗粒可以在管道中沉降,从而促进沉积物捕获和沉降速率。我们的结果表明,洞穴的纵横比显着影响有机物质和沉积物颗粒的捕获过程。此外,这种捕获机制取决于流动状态,因为较快的流动与水柱中的大量物质有关。
更新日期:2019-12-11
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