Coarse-grained hard substrate areas with grain sizes up to very coarse boulder (> 2 m) are very rare in the German North Sea. The “Helgoländer Steingrund” is one of such highly biodiverse areas: it is characterized by a half-moon-shaped hard substrate ridge, which subdivides the site into a more exposed (westerly) and a less exposed (easterly) flank, characterized by a mixture of sand and gravel deposits. Sonar systems, underwater videos, and bottom samples were used for mapping and classifying the abiotic and biotic components in such very patchy and coarse-grained habitat. Three main seabed types (sand, gravel, and hard substrate) were identified, based on acoustic backscatter data. The additional information coming from underwater videos and sediment bottom sample analysis allowed the description of six different seabed types, which included both the abiotic (sediments, morphology, etc.) and biotic components. The flanks of the ridge and their transition to the surrounding soft-ground areas were characterized by a distinct dominance of the bryozoa F. foliacea and A. diaphanum on the western and on the eastern side, respectively. Morphology and hydrodynamics are likely responsible for such zonation. This is proved by the outcomes of the Acoustic Doppler Current Profiler data, which showed the general flow pattern across the ridge and even resolved the local variability of current pattern, dependent on the tidal stage and bottom relief.

中文翻译：

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德国湾粗粒栖息地底栖海底的流体动力学和水声测绘

在德国北海，具有高达非常粗的巨石 (> 2 m) 的粗粒硬质基底区域非常罕见。“Helgoländer Steingrund”是生物多样性如此丰富的地区之一：它的特点是有一个半月形的硬底脊，将场地细分为暴露程度较高（西风）和暴露较少（东风）的侧面，其特点是砂和砾石沉积物的混合物。声纳系统、水下视频和底部样本被用于绘制和分类这种非常不完整和粗粒度的栖息地中的非生物和生物成分。根据声学反向散射数据，确定了三种主要海床类型（沙子、砾石和硬质基底）。来自水下视频和沉积物底部样本分析的附加信息允许描述六种不同的海床类型，其中包括非生物（沉积物、形态等）和生物成分。山脊的侧翼及其向周围软地面区域的过渡的特点是苔藓虫 F. foliacea 和 A. diaphanum 分别在西部和东部具有明显优势。形态学和流体动力学可能是造成这种分区的原因。声学多普勒海流剖面仪数据的结果证明了这一点，该数据显示了穿过海脊的一般流动模式，甚至解决了取决于潮汐阶段和底部起伏的电流模式的局部变化。diaphanum 分别位于西部和东部。形态学和流体动力学可能是造成这种分区的原因。声学多普勒海流剖面仪数据的结果证明了这一点，该数据显示了穿过海脊的一般流动模式，甚至解决了取决于潮汐阶段和底部起伏的电流模式的局部变化。diaphanum 分别位于西部和东部。形态学和流体动力学可能是造成这种分区的原因。声学多普勒海流剖面仪数据的结果证明了这一点，该数据显示了穿过海脊的一般流动模式，甚至解决了取决于潮汐阶段和底部起伏的电流模式的局部变化。